33 BMW 1983 R80ST Rebuild Rear Drive

I suspect the final drive seals are leaking, and this bike has been sitting for about 25 years. So I am rebuilding and refinishing the rear drive. I have never rebuilt a rear drive before and I understand this requires some special tools and also correct shimming of the pinion and crown gear; aka, ring gear. So I asked Matt Iles, owner of Iles Motorsports, if I could watch him do this work, and he agreed. I have Matt replace all the seals and bearings in the final drive so it will be good for another 40 years and 100,000 miles. ūüôā That way I get an education about how this is done so I can decide if I am capable of doing this work in the future. Any mistakes in this documentation are on me, not Matt.

WARNING:
This is precision work and requires several special tools to complete the work. For this reason, only those who have the special tools and experience should attempt to rebuild a rear drive on their own. Should the rear drive fail, it can be a very dangerous experience.

Matt was gracious in donating his labor in support of my goal to auction this bike and donate all the proceeds to the Motorcycle Relief Project. He is also the person who pointed to this bike when I let him know that I wanted to rebuild and R80ST for charity.

Tools

This tool is a strip of steel with holes that match the studs in the rear drive that attach the swing arm. It’s a handy way to hold the rear drive in a vice while working on it.

Rear Drive Bracket

Rear Drive Bracket

Rear Drive Bracket Secured In Vice

Rear Drive Bracket Secured In Vice

This tool is a large diameter pin wrench that removes the threaded ring with the seal that fits around the shaft of the pinion gear. It’s BMW part # (33 1 700) and is available from MAX BMW as part # (83 30 0 402 060).

Pinion Shaft Seal Ring Pin Wrench

Pinion Shaft Seal Ring Pin Wrench

Pin Wrench For Removing Pinion Shaft Seal Ring: BMW Part# 33 1 700

Pin Wrench For Removing Pinion Shaft Seal Ring: BMW Part# 33 1 700

This tool that fits on the input gear of the pinion gear shaft. The input gear mates with the driveshaft coupling. It prevents the pinion shaft from turning when removing the pinion shaft nut.

Tool To Immobilize Pinion Shaft

Tool To Immobilize Pinion Shaft

A variety of blind pullers and bearing separators are needed to remove bearings from shafts.

Blind Bearing Puller

Blind Bearing Puller

Bearing Separator

Bearing Separator

Bearing Puller

Bearing Puller

A gas torch, or two, are also needed to heat parts of the aluminum rear drive housing to remove bearings without scoring the aluminum. Propane or MAP gas torches will work.

Gas Torches

Gas Torches

Parts

Here is the list of new parts I use to rebuild the rear drive.

Part #                   Description                                                               Qty
23 21 1 230 084  COLLAR NUT 1
33 12 1 233 302  GASKET RING 1
33 11 2 311 097  GASKET ASBESTOS FREE 1
33 12 1 230 247  ANGULAR BALL BEARING 1
33 12 1 231 542  SHAFT SEAL 1
33 12 1 236 998  NEEDLE SLEEVE Р15X30X18 1
33 12 1 241 682  NEEDLE BEARING 1
33 12 1 242 211  GROOVED BALL BEARING Р85X120X18 1
33 12 1 241 938  SHAFT SEAL Р85X110X10 1

Disassemble Rear Drive

Matt mounts the rear drive in the steel strap in his vice so it is easy to work on it.

Securing Rear Drive In Bracket

Securing Rear Drive In Bracket

Remove Pinion Gear Shaft

Then he uses the input gear immobilizing tool to prevent the pinion shaft from turning. He heats the nut on the end of the pinion shaft as it has loctite on it and then removes the nut and washer.

Install Tool To Immobilize Pinion Shaft

Install Tool To Immobilize Pinion Shaft

Heating Pinion Shaft Nut To Loosen Loctite

Heating Pinion Shaft Nut To Loosen Loctite

Removing Pinion Shaft Nut

Removing Pinion Shaft Nut

Pinion Shaft Nut And Washer

Pinion Shaft Nut And Washer

There is a plastic seal in the face of the pinion shaft input gear that he removes. It’s old and comes out in pieces. Then he removes the pinion shaft input gear.

Pinion Shaft Input Gear Gasket Ring

Pinion Shaft Input Gear Gasket Ring

Removing Pinion Shaft Input Gear Gasket Ring

Removing Pinion Shaft Input Gear Gasket Ring

Pieces Of Pinion Shaft Input Gear Gasket Ring

Pieces Of Pinion Shaft Input Gear Gasket Ring

Removing Pinion Shaft Input Gear

Removing Pinion Shaft Input Gear

Pinion Shaft Input Gear

Pinion Shaft Input Gear

The pinion shaft seal ring has a seal and screws into the rear drive housing. Matt heats the side of the rear drive housing around the larger ball bearing so he can remove the pinion gear shaft. He uses the large pin wrench to unscrew the seal ring. Behind it is a large shim.

Heating Rear Drive Housing To Remove Pinion Shaft Seal Ring

Heating Rear Drive Housing To Remove Pinion Shaft Seal Ring

Pinion Shaft Seal Ring Pin Wrench

Pinion Shaft Seal Ring Pin Wrench

Installing Pinion Shaft Seal Ring Pin Wrench

Installing Pinion Shaft Seal Ring Pin Wrench

Pinion Shaft Seal Ring Removed

Pinion Shaft Seal Ring Removed

Pinion Shaft Seal In Ring

Pinion Shaft Seal In Ring

Pinion Shaft Shim

Pinion Shaft Input Gear Shim

There is a double ball bearing race on the pinion gear shaft. Matt uses the pinion shaft nut to pull the shaft out of the rear drive housing. Matt heats the rear drive housing around the bearing and then uses pliers to pull the pinion gear shaft out.

NOTE:
If the pinion shaft won’t come out by hand, you need to heat the rear drive housing around the double ball bearing more. That said, sometimes some gentle persuasion is needed, but not much.

Heating Rear Drive To Remove Pinion Shaft Assembly

Heating Rear Drive To Remove Pinion Shaft Assembly

Removing Pinion Shaft Assembly

Removing Pinion Shaft Assembly

 

Pinion Shaft Shims

Pinion Shaft Shims

Pinion Shaft Shims

Pinion Shaft Shims

Pinion Shaft Parts-Ring Seal In Background

Pinion Shaft Parts-Ring Seal In Background

Remove Rear Cover And Seal

The rear cover is secured with eight bolts with wave washers. The cover fits tightly inside the rear drive housing. There are two M5 threaded holes in the cover. Matt screws in two long M5 bolts to push the rear cover out of the lip in the rear drive case. He had to heat the case to help get the rear cover loose. Matt uses a large blade screw driver and hammer to remove the large diameter oil seal from the rear cover.

Rear Drive Cover Is Secured By 8 Bolts

Rear Drive Cover Is Secured By 8 Bolts

Orienting Rear Drive To Remove Cover

Orienting Rear Drive To Remove Cover

Rear Drive Cover Hardware Detail

Rear Drive Cover Hardware Detail

Hole In Rear Drive Cover For 5 mm Bolt To Push The Cover Out Of Rear Drive Housing

Hole In Rear Drive Cover For 5 mm Bolt To Push The Cover Out Of Rear Drive Housing

Inserting 5 mm Bolt Into Rear Drive Cover

Inserting 5 mm Bolt Into Rear Drive Cover

 

Evenly Tightening 5 mm Bolts To Remove Rear Drive Cover From Rear Drive Housing

Evenly Tightening Both 5 mm Bolts To Remove Rear Drive Cover From Rear Drive Housing

Rear Drive Drive Cover Removed

Rear Drive Drive Cover Removed

Rear Drive Drive Cover Gasket

Rear Drive Drive Cover Gasket

Rear Drive Cover Oil Seal

Rear Drive Cover Oil Seal

Rear Drive Cover Seal Removed

Rear Drive Cover Seal Removed

Remove Crown Gear Shaft

After the rear cover is removed, the crown gear shims are exposed. Matt removes the crown gear assembly and the needle bearing the nose of the crown gear rides inside of. There is a brass compression ring on the nose of the crown gear that fits on the face of the roller bearing and acts as a shim.

Rear Drive Drive Cover Removed Showing Shims On Crown Gear Shaft

Rear Drive Drive Cover Removed Showing Shims On Crown Gear Shaft

Crown Gear Shaft Shims

Crown Gear Shaft Shims

Crown Gear Shaft Shims

Crown Gear Shaft Shims

Removing Crown Gear Shaft

Removing Crown Gear Shaft

Crown Gear Shaft Needle Bearing Removed

Crown Gear Shaft Needle Bearing Removed

Crown Gear Shaft Compression Ring Acts As A Shim

Crown Gear Shaft Compression Ring Acts As A Shim

Under the crown gear is a metal pan the fits in the rear drive housing and Matt lifts it out of the housing.

Rear Drive Case With Metal Pan

Rear Drive Case With Metal Pan

Metal Pan Removed

Metal Pan Removed

Rear Drive Housing With Parts Removed

Rear Drive Housing With Parts Removed

Rear Drive Case Casting Mark

Rear Drive Case Casting Mark

Remove Crown Gear Bearings

The crown gear needle bearing outer race fits on the nose of the crown gear shaft. Matt uses a bearing splitter and a puller to remove it.

Crown Gear Shaft Needle Bearing Outer Race

Crown Gear Shaft Needle Bearing Outer Race

Removing Crown Gear Shaft Needle Bearing Outer Race

Removing Crown Gear Shaft Needle Bearing Outer Race

Removing Crown Gear Shaft Needle Bearing Outer Race

Removing Crown Gear Shaft Needle Bearing Outer Race

Removing Crown Gear Ball Bearing Outer Race Removed

Removing Crown Gear Needle Bearing Outer Race Removed

Removing Crown Gear Needle Bearing Race

Removing Crown Gear Needle Bearing Race

Matt uses a larger bearing puller to remove the large diameter ball bearing race from the crown gear. He puts a large socket in the hole between the rear wheel studs for the bearing puller to press on.

Crown Gear Shaft Ball Bearing Race

Crown Gear Shaft Ball Bearing Race

Using Socket For Gear Puller To Push On

Using Socket For Gear Puller To Push On

Removing Crown Gear Ball Bearing Race

Removing Crown Gear Ball Bearing Race

Removing Crown Gear Ball Bearing Race

Removing Crown Gear Ball Bearing Race

Removing Crown Gear Ball Bearing Race

Removing Crown Gear Ball Bearing Race

Crown Gear Ball Bearing Race Removed

Crown Gear Ball Bearing Race Removed

Crown Gear & Ball Bearing Race

Crown Gear & Ball Bearing Race

Remove Pinion Gear Shaft Rear Needle Bearing

The pinion gear shaft rear end rides in a needle bearing inside a hole in the rear drive housing. Matt removes the bearing race from the rear drive housing with a blind puller. He heats the aluminum housing around the bearing to sizzle hot before removing the bearing so as not to score the aluminum.

Location Of Pinon Shaft Rear Needle Bearing In Rear Drive Housing

Location Of Pinion Shaft Rear Needle Bearing In Rear Drive Housing

Removing Pinon Gear Shaft Needle Bearing With Blind Bearing Puller

Removing Pinion Gear Shaft Needle Bearing With Blind Bearing Puller

Kuko Bearing Puller Part No (21-4)

Kuko Bearing Puller Part No (21-4)

Removing Pinon Gear Shaft Needle Bearing

Removing Pinion Gear Shaft Needle Bearing

Removing Pinon Gear Shaft Needle Bearing With Bearing Puller And Flange To Protect The Rear Drive/Swing Arm Mating Surface

Removing Pinion Gear Shaft Needle Bearing With Bearing Puller And Flange To Protect The Rear Drive/Swing Arm Mating Surface

Heating Aluminum Housing Around Pinon Gear Shaft Needle Bearing

Heating Aluminum Housing Around Pinion Gear Shaft Needle Bearing

Pinon Gear Shaft Needle Bearing Removed

Pinion Gear Shaft Needle Bearing Removed

Pinon Gear Shaft Needle Bearing

Pinion Gear Shaft Needle Bearing

Remove Pinion Gear Bearings

Matt removes the pinion gear needle bearing outer race from the pinion bearing shaft using a bearing splitter and puller. Then he removes the pinion gear and washer.

Pinon Shaft Needle Bearing Outer Race

Pinion Shaft Needle Bearing Outer Race

Removing Pinon Shaft Needle Bearing Outer Race

Removing Pinion Shaft Needle Bearing Outer Race

Removing Pinon Shaft Needle Bearing Outer Race

Removing Pinion Shaft Needle Bearing Outer Race

Pinon Shaft Needle Bearing Outer Race Removed

Pinion Shaft Needle Bearing Outer Race Removed

Matt uses a gear splitter and his press to remove the pinion gear double ball bearing race.

Pinon Shaft Double Ball Bearing Race

Pinion Shaft Double Ball Bearing Race

Bearing Splitter Under Pinon Gear Shaft Double Ball Bearing Race

Bearing Splitter Under Pinion Gear Shaft Double Ball Bearing Race

Pressing The Pinon Gear Shaft Out Of The Ball Bearing Race

Pressing The Pinion Gear Shaft Out Of The Double Ball Bearing Race

Pressing The Pinon Gear Shaft Out Of The Double Ball Bearing Race

Pressing The Pinion Gear Shaft Out Of The Double Ball Bearing Race

Pinon Gear Shaft Double Ball Bearing Race

Pinion Gear Shaft Double Ball Bearing Race

Pinon Gear Shaft Parts

Pinion Gear Shaft Parts

Vapor Blast Rear Drive

I took the rear drive housing and cover plate to Bryan Flanagan at Colorado Vapor Blasting to have them vapor blasted. Here is the before and after pictures.

Rear Drive Case Before Vapor Blasting

Rear Drive Case Before Vapor Blasting

Rear Drive Cover Before Vapor Blasting

Rear Drive Cover Before Vapor Blasting

Rear Drive Case Before Vapor Blasting

Rear Drive Case Before Vapor Blasting

Rear Drive After Vapor Blasting

Rear Drive After Vapor Blasting

Rear Drive After Vapor Blasting

Rear Drive After Vapor Blasting

Rear Drive After Vapor Blasting

Rear Drive After Vapor Blasting

Rear Drive Cover Casting Marks

Rear Drive Cover Casting Marks

Rear Drive After Vapor Blasting

Rear Drive After Vapor Blasting

Assemble Rear Drive

It took a bit more than 2 months to get the parts for the rear drive rebuild. I went back to Matt Iles’ shop to watch how he installed the new parts and checked the shimming of the pinion gear shaft and crown gear shaft. Before beginning work, he thoroughly cleans the inside of the rear drive housing with brake cleaner to be sure there is no debris or fine particles from the vapor blasting inside the housing.

Rear Drive Parts Laid Out

Rear Drive Parts Laid Out

Cleaning Inside Of Rear Drive Housing

Cleaning Inside Of Rear Drive Housing

The procedure Matt follows alternates installing the bearings on the pinion and crown gear shafts since the bearings get heated to slide them on the shafts and they need to cool before adding the next bearing so they stay where they need to be and don’t move.

The crown gear and the pinion gear are sold as a matched set. They are engraved with the same number after being matched at the factory to ensure you are installing a matched set of gears. Mine are marked “750”.

Pinon Gear Number 750

Pinion Gear Number 750

Crown Gear Number 750

Crown Gear Number 750

Install Crown Gear Shaft Ball Bearing Race

Matt uses a skillet to heat the bearings to sizzle hot before installation. The crown gear shaft ball bearing dropped into place.

Heating Crown Ring Gear Ball Bearing Race In Electric Skillet

Heating Crown Ring Gear Ball Bearing Race In Electric Skillet

Crown Gear Ball Bearing Race Installed

Crown Gear Shaft Ball Bearing Race Installed

Install Pinion Gear Shaft Needle Bearing Inner Bearing Race

The pinion gear inner bearing race fits on the end of the pinion shaft. The inner race has a face that has a flat end and a face with a bevel around the hole. The bevel side of the inner race faces the pinion gear. It dropped into place as well.

Pinon Gear Shaft Location For Inner Needle Bearing Race

Pinion Gear Shaft Location For Inner Needle Bearing Race

Pinon Gear Shaft Inner Needle Bearing Race-Flat Face

Pinion Gear Shaft Inner Needle Bearing Race-Flat Face

Pinon Gear Shaft Inner Needle Bearing Race-Beveled Face

Pinion Gear Shaft Inner Needle Bearing Race-Beveled Face

It dropped into place as well.

Pinon Gear Shaft Inner Needle Bearing Race Installed

Pinion Gear Shaft Inner Needle Bearing Race Installed

Install Crown Gear Shaft Needle Bearing Inner Race

The crown gear needle bearing inner race faces are the same. Matt heats it in the skillet and then drops it onto the end of the crown gear shaft.

Crown Gear Shaft Inner Needle Bearing Race

Crown Gear Shaft Inner Needle Bearing Race

Heating Crown Gear Inner Needle Bearing Race

Heating Crown Gear Inner Needle Bearing Race

Crown Gear Shaft Inner Needle Bearing Race Installed

Crown Gear Shaft Inner Needle Bearing Race Installed

Install Pinion Shaft Ball Bearing Race

Matt heats the pinion shaft ball bearing race and then slides onto the shaft.

Installing Pinon Shaft Needle Bearing Outer Race

Installing Pinion Shaft Ball Bearing Race

Pinon Gear Shaft Ball Bearing Race Installed

Pinion Gear Shaft Ball Bearing Race Installed

Install Pinion Gear Shaft Needle Bearing Outer Race

The pinion gear shaft needle bearing outer race fits into a hole in the rear drive housing. Matt heats the housing around the hole to sizzle hot with a heat gun. Then he uses an adjustable bearing race driver tool that accepts different size pucks to drive the pinion shaft outer needle bearing race into the hole.

Heating Rear Drive Housing Around Pinon Shaft Needle Bearing Hole In The Center Of The Housing

Heating Rear Drive Housing

Adjustable Bearing Race Driver Tool

Adjustable Bearing Race Driver Tool

Changing Adjustable Bearing Driver Puck

Changing Adjustable Bearing Driver Puck

Driving Pinon Shaft Needle Bearing Into Hole In Rear Drive Housing

Driving Pinion Shaft Needle Bearing Into Hole In Rear Drive Housing

Driving Pinon Shaft Needle Bearing Outer Race Into Hole In Rear Drive Housing

Driving Pinion Shaft Needle Bearing Outer Race Into Hole In Rear Drive Housing

Install Crown Gear Shaft Outer Needle Bearing & Crown Gear Shaft

Matt reheats the rear drive housing and then drops in the crown gear shaft outer needle bearing. Then he installs the crown gear shaft shim on the center of the hole.

Crown Gear Shaft Outer Needle Bearing Race Installed In Rear Drive Housing

Crown Gear Shaft Outer Needle Bearing Race Installed In Rear Drive Housing

Crown Gear Shaft Shim Installed In Rear Drive Housing Hole

Crown Gear Shaft Shim Installed In Rear Drive Housing Hole

Install Pinion Gear Shaft In Rear Drive Housing

Next, Matt mounts the rear drive housing in a special clamp in his vice. He heats the inside of the ball bearing hole to sizzle hot. Then he installs the pinion shaft shim and then the pinion shaft ball bearing on top of the shim and drives it home.

Rear Drive Housing Mounted In Bracket In Vice

Rear Drive Housing Mounted In Bracket In Vice

Ready To Install Pinon Gear Shaft Into Rear Drive Housing

Ready To Install Pinion Gear Shaft Into Rear Drive Housing

Pinon Gear Shaft Shim

Pinion Gear Shaft Shim

Rear Needle Bearing For Pinon Gear Shaft

Rear Needle Bearing For Pinion Gear Shaft

Installing Pinon Gear Assembly Into Rear Drive Housing

Installing Pinion Gear Assembly Into Rear Drive Housing

Pinon Gear Installed In Rear Drive Housing

Pinion Gear Installed In Rear Drive Housing

Next he installs the pinion shaft seal into the seal carrier using his adjustable bearing driver. The flat face of the seal points toward the inside of the rear drive housing and the side with the spring around the hole faces to the outside. The shaft seal face with the spring fits into the carrier so it faces the end of the carrier with the larger gap between the end of the threads and the end of the carrier.

Pinon Shaft Seal

Pinion Shaft Seal

Pinon Shaft Seal Orientation Inside Seal Carrier

Pinion Shaft Seal Orientation Inside Seal Carrier

Pinon Shaft Seal-Inside Face When Installed

Pinion Shaft Seal-Inside Face When Installed

Install Seal In Pinon Seal Housing With Seal Driver

Install Seal In Pinion Seal Housing With Seal Driver

He then puts some Hylomar on the threads of the seal carrier. Then he installs the washer on top of the pinion gear shaft ball bearing. He uses a special tool to screw the shaft seal carrier into the rear drive housing and torques it to the torque specification for the R80ST.

Hylomar Gasket Sealer

Hylomar Gasket Sealer

Applying Hylomar to Pinon Gear Shaft Seal Housing Threads

Applying Hylomar to Pinion Gear Shaft Seal Housing Threads

Hylomar Applied Pinon Gear Shaft Seal Housing Threads

Hylomar Applied Pinion Gear Shaft Seal Housing Threads

Pinon Gear Shaft Seal Carrier Threads

Pinion Gear Shaft Seal Carrier Threads

Part Number Of BMW Pinon Gear Seal Carrier Tool

Part Number Of BMW Pinion Gear Shaft Seal Carrier Tool

Install Pinon Gear Shaft Seal Carrier

Install Pinion Gear Shaft Seal Carrier

Install Pinon Gear Shaft Seal Carrier

Install Pinion Gear Shaft Seal Carrier

Torque Pinon Gear Seal Carrier Into Rear Drive Housing

Torque Pinion Gear Seal Carrier Into Rear Drive Housing

Install Pinion Drive Gear

Since we did not replace the crown gear and pinion gear shafts, the existing shims should be the correct thickness. Matt will determine if this is true after installing the pinion gear shaft driving gear.

Matt installs the pinion gear shaft washer, the pinion gear shim and the pinion gear seal, the pinion gear shaft driving gear, the washer and the bolt and torques it to the R80ST specification.

Installing Pinon Gear Shaft Washer

Installing Pinion Gear Shaft Washer

Pinon Gear Shaft Washer Installed

Pinion Gear Shaft Washer Installed

Pinon Gear Shaft Shim Installed On Top OF Washer

Pinion Gear Shaft Shim Installed On Top OF Washer

Pinon Shaft Seal Orientation

Pinion Shaft Seal Orientation

Pinon Shaft Input Gear Seal

Pinion Shaft Input Gear Seal

Pinon Gear Shaft Washer And Nut

Pinion Gear Shaft Washer And Nut

Using Pinion Gear Tool To Torque Pinion Shaft Nut

Using Pinion Gear Tool To Torque Pinion Shaft Nut

Determine Gear Teeth Mesh Pattern

Matt applies gear mesh grease to some of the crown gear teeth. This is a grease with a coloring agent. He installs the crown gear and pushes down on the hub while he spins the hub so the crown gear meshes with the pinion gear. Then he checks the pattern of the grease removed at the contact line of the gear teeth. Comparing them to the correct and incorrect pattern shown in the Clymer’s manual, the pattern is the same as the correct gear teeth mesh pattern. This implies that the crown and pinion gear shaft shims are the correct size to move the shafts to the correct position for the gear teeth to mesh in the center of the teeth. Then Matt cleans much of the measuring grease off the teeth, but since it’s grease, if some is left behind it won’t harm anything.

Gear Teeth Mesh Grease

Gear Teeth Mesh Grease

Gear Mesh Grease Applied To A Few Crown Gear Teeth

Gear Mesh Grease Applied To A Few Crown Gear Teeth

Twisting Crown Gear To See The Gear Teeth Mesh Pattern

Twisting Crown Gear To See The Gear Teeth Mesh Pattern

Crown Gear Teeth Mesh Pattern

Crown Gear Teeth Mesh Pattern

Crown Gear Teeth Mesh Pattern

Crown Gear Teeth Mesh Pattern

Pinon Gear Teeth Mesh Pattern

Pinion Gear Teeth Mesh Pattern

Pinon Gear Teeth Mesh Pattern

Pinion Gear Teeth Mesh Pattern

Correct Gear Teeth Mesh Pattern

Correct Gear Teeth Mesh Pattern

Incorrect Gear Teeth Mesh Patterns

Incorrect Gear Teeth Mesh Patterns

Measure Required Shim Thickness

Next Matt measures the rear cover depth of the shoulder for the large crown gear ball bearing. He measures the depth between the top of the crown gear ball bearing and the contact surface for the rear cover on the rear drive housing. He uses a jig to center the crown gear large ball bearing. Then he measures the thickness of the two existing shims and the thickness of the new cover gasket.

Measuring Depth Of Crown Ring Gear Bearing Hole In Rear Cover

Measuring Depth Of Crown Ring Gear Bearing Hole In Rear Cover

Crown Ring Gear Height Measurement Plate

Crown Gear Height Measurement Plate Aligns Ball Bearing In Rear Drive Housing

Crown Ring Gear Edge For Height Measurement

Crown Gear Ball Bearing Edge For Height Measurement

Rear Drive Case Crown Ring Gear Edge For Height Measurement

Rear Drive Case Edge For Crown Gear Ball Bearing Height Measurement

Measuring Crown Ring Gear Height

Measuring Crown Gear Ball Bearing Height

Measuring Two Crown Gear Shaft Shims

Measuring Two Crown Gear Shaft Shims

As shown below, the cover depth is 16.97 mm, the ball bearing height in the housing is 16.01 mm, the two shims are 1.13 mm thick. The gasket thickness is 0.28 mm. The difference between the cover depth and housing is 0.96 mm. Subtracting that from the shims gives 0.17 mm and subtracting that from the gasket thickness gives 0.11 mm. Since the gasket will compress a bit when the rear cover bolts are torqued, the bearing end play specification of 0.10 mm should be met so there is no need to change the shims.

Measurements Of Crown Ring Gear End Play-Conclusion Is End Play Is Okay

Measurements Of Crown Ring Gear End Play-Conclusion Is End Play Is Okay

Measure Gear Backlash

Next, Matt measures the backlash of the crown and pinion gears using a special tool and a dial indicator. Backlash is the amount of rotation of the hub without moving the pinion gear. Matt installs the rear cover aligning the rear brake cam shaft hole in the cover with the hole in the rear drive case. He typically uses the brake pivot rod to align the holes, but since I didn’t bring it, he uses a deep socket that is close to the same diameter. He torques the cover bolts to specification.

Hole For Brake Cam Shaft In Rear Drive Cover

Hole For Brake Cam Shaft In Rear Drive Cover

Align Brake Cam Hole In Cover With Hole In Rear Drive Housing

Align Brake Cam Hole In Cover With Hole In Rear Drive Housing

Torque Rear Drive Cover Bolts

Torque Rear Drive Cover Bolts

Then he installs the special tool on the three studs of the rear drive. The tool has a mark indicating where the backlash measurement is taken with the dial indicator. He immobilizes the pinion drive using another special tool.

Install Rear Drive Gears Backlash Measurement Tool

Install Rear Drive Gears Backlash Measurement Tool

Rear Drive Gears Backlash Tool Installed On Hub Bolts

Rear Drive Gears Backlash Tool Installed On Hub Bolts

Rear Drive Gears Backlash Tool Has Measurement Mark (RED)

Rear Drive Gears Backlash Tool Has Measurement Mark (RED)

Mark For Where Dial Indicator Touches Rear Drive Gears Backlash Tool

Mark For Where Dial Indicator Touches Rear Drive Gears Backlash Tool

Special Tool To Immobilize Pinon Gear Shaft

Special Tool To Immobilize Pinion Gear Shaft

He installs the dial indicator using a magnet to hold it steady on the vice and an articulate arm to position the pointer of the dial indicator at the red line and perpendicular to the arm. Then he turns the hub to lock the crown gear teeth against the pinion gear teeth. He zeros the dial indicator in this position and then rotates the hub in the opposite direction to measure the amount of backlash. If is 0.13 mm and the maximum allowed is 0.14 mm, so the backlash is within specifications.

Mounting Dial Indicator For Measuring Rear Drive Gears Backlash

Mounting Dial Indicator For Measuring Rear Drive Gears Backlash

Dial Indicator Tip Positioned On Arm Of Measurement Tool

Dial Indicator Tip Positioned On Arm Of Measurement Tool

Rotating Hub To Measure Rear Drive Gears Backlash

Rotating Hub To Measure Rear Drive Gears Backlash

Measuring Rear Drive Gears Backlash-0.13 mm

Measuring Rear Drive Gears Backlash-0.13 mm

Final Install Of Rear Cover

Matt takes the rear cover off again. He installs the metal pan and lubricates the gears with 80W-90 gear lube. He installs the rear cover gasket on the rear drive housing. He heats the rear drive cover and installs the rear cover over the hub again aligning the brake cam shaft holes in the rear cover and the rear drive case. Then he installs the crown gear assembly and rear cover into the rear drive housing and torques the cover bolts to specification.

Remove Rear Cover Bolts

Remove Rear Cover Bolts

Pan Installed In Rear Drive Housing

Pan Installed In Rear Drive Housing

Lubing Rear Drive Bearings With 80W-90 Gear Lube

Lubing Rear Drive Bearings With 80W-90 Gear Lube

Lubing Rear Drive Bearings With 80W-90 Gear Lube

Lubing Rear Drive Bearings With 80W-90 Gear Lube

Rear Drive Cover Gasket Detail

Rear Drive Cover Gasket Detail

Lubing Rear Drive Bearings With 80W-90 Gear Lube

Lubing Rear Drive Bearings With 80W-90 Gear Lube

New Rear Drive Cover Seal

New Rear Drive Cover Seal

Drift For Installing Rear Drive Cover Seal

Drift For Installing Rear Drive Cover Seal

Installing Rear Drive Cover Seal In Rear Drive Cover

Installing Rear Drive Cover Seal In Rear Drive Cover

Rear Drive Cover Seal Edge Even With Edge Of Rear Drive Cover

Rear Drive Cover Seal Edge Even With Edge Of Rear Drive Cover

Heating Rear Drive Cover And Coating Seal Edge With 80W-90 Gear Lube

Heating Rear Drive Cover And Coating Seal Edge With 80W-90 Gear Lube

Rear Drive Cover Seal Installed Around Hub

Rear Drive Cover Seal Installed Around Hub

Cleaning Rear Drive Cover Mating Surface

Cleaning Rear Drive Cover Mating Surface

Installing Crown Gear Assembly And Rear Drive Cover On Rear Drive

Installing Crown Gear Assembly And Rear Drive Cover On Rear Drive

What All Done Looks Like

Here is what we started with and how the rear drive looks after vapor blasting and rebuilding it.

Original Rear Drive Before Removal From Swing Arm

Original Rear Drive Before Removal From Swing Arm

Rear Drive Case Before Vapor Blasting

Rear Drive Case Before Vapor Blasting

Vapor Blasted, Rebuilt Rear Drive

Vapor Blasted, Rebuilt Rear Drive

Vapor Blasted, Rebuilt Rear Drive

Vapor Blasted, Rebuilt Rear Drive

Vapor Blasted, Rebuilt Rear Drive

Vapor Blasted, Rebuilt Rear Drive

2 thoughts on “33 BMW 1983 R80ST Rebuild Rear Drive

  1. Thank you very much for your great documentation. I always wanted to see this work. I’m not able to do it because I don’t own the tools for this precise work. Well done! Greetings from Germany

    Lupo

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.