First off, regardless of what you want to do to your rear drive, read both of Pete Roper's articles (hosted at the GuzziTech website). Better yet, read through them a few times to get a really good understanding of what these boxes are designed to do and how to repair them.

Pete's first article: Rear Drive Tear Down
Pete's second article: Rear Drive Rant #2

Now, I'll try to provide some insight from a first-timer's perspective. This information is only intended to supplement Pete's articles.

Items you will want to replace, regardless

MG# 90403850 - The small outer seal (these are the same for all big twins)
MG# 90407085 - The large inner seal (these are the same for all big twins)
MG# 90706490 - The large o-ring that goes between the pinion carrier and the rear drive housing
MG# 12352600 - The paper gasket that goes between the pinion carrier and the rear drive housing.
MG# 12352900 - The paper gasket that goes between the pinion carrier and the swing arm.
MG# 12350700 - The paper gasket that goes on either side of the shim between the flange and the body of the rear drive.
Replace all of the washers and bendy-tabs with Schnorr washers.

Items you may want to replace, depending on condition

MG# 92249225 - Pinion carrier bearings.
MG# 92201070 - Large ball bearing pressed into the flange.
MG# 92254340 - Needle bearing.

Special tools that are very helpful if not required

Half of an old, worn out U-Joint - If you don't have one in your own stash, check with your local dealer or with friends.
Two-jaw puller - I just bought a cheap one from Harbor Freight because I ended up grinding on it to make it able to remove the inner race of the needle bearing.
Slide hammer puller - I bought a cheap one from Harbor Freight. The attachments are weak and mostly worthless, but end up making my own using bolts that I grind for specific uses.
Betty Crocker Roaster Oven - Home Depot seems to sell these each year during the holiday season for around USD $30.00. Money well spent.
Torque wrench - Nothing fancy here, just something that goes form about 10 to 50 foot pounds is great.
36 mm box-end wrench (or a 1 7/16" box-end wrench if you can't find one of those)

Things I learned the first time around

Get the tools listed above before you start the tear down.
Removing the outer race for the needle bearing is much easier if you use the oven technique Pete describes. Plus, you probably won't ruin the brass ring. But, it is very stinky. I'm still in the doghouse with my wife Angela for using the oven in the kitchen. Now I have the Betty Crocker Roaster Oven and it works great.
Forget messing around with the old bendy-tabs and lock washers...replace them all with Schnorr washers and be done with it.
When installing the small outer seal, be sure to install it properly. As you are looking into the housing (as if it were a bucket), the flat surface of the seal should be on the bottom. If you get it backwards, your rear drive will leak (ask me how I know this).
There is no need to use gasket sealant on any of the gaskets. My experience is that they gaskets seal quite well with just a coating of grease on them.
Do use a high quality spline grease on all of the splines. Do not use wheel bearing grease or any other typical grease. It will only heat up, turn to liquid, and get flung all over your rear wheel (ask me how I know this). Instead, use something like Amsoil Fifth Wheel and Open Gear Compound.

Rear drive bearing cross-references

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There are three different types of bearings that are used in the rear drive. All are open (not shielded or sealed).

One (1) large ball bearing (ID: 70 mm, OD: 110 mm, Width: 13 mm)
This is the same bearing that has been used in all Moto Guzzi big twin rear drives from the V7 / V700 in 1968 through to this day, with the possible exception of some of the newer sport rear drives.
- Moto Guzzi MG# 92201070
- Maryland Metric item no. 16014
- SKF 16014
- FAG 16014
- RIV ELn 70
- STEYR 16014
One (1) needle bearing (ID: 40 mm, OD: 55 mm, Width: 17 mm)
This is the same bearing that has been used in all Moto Guzzi big twin rear drives from the V7 / V700 in 1968 through to this day, with the possible exception of some of the newer sport rear drives.
- Moto Guzzi MG# 92254340
- FAG NAO 40 x 55 x 17
- FAG (Old No.) NAF 40 x 55 x 17
- INA NAO 40 x 55 x 17
- SKF (Old No.) NAF 40 x 55 x 17
- SKF (Eur.) NAO 40 x 55 x 17
Two (2) tapered roller bearings (ID: 25 mm, OD: 52 mm, Width: 16.25 mm)
This is the same bearing that has been used in all REAR DRUM BRAKE Moto Guzzi big twin rear drives from the V7 / V700 in 1968 through to the 850T and V7 Sport.
- Moto Guzzi MG# 92249225
- Maryland Metric item no. 30205
- FAG 30205A
- RIV 01/02/7205
- SKF 30205A
- SNR 30205
- STEYR 30205

Rear drive leaks

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When I first restored my Ambassador, I replaced the large inner seal (MG# 90407085) in the rear drive as well as the two gaskets (MG# 12350700) that are sandwiched between the flange and the rear drive box.

After a few miles, I quickly realized that this did not solve all of my problems. So I also replaced the small outer seal (MG# 90403850). During both my seal replacements, I was careful to clean and polish the mating surfaces.

But I was still getting stuff flung all over my newly polished rear rim (and on to the tire, which is less than safe!). When I parked, nothing leaked on the ground, but there was definite evidence that something was leaking.

I brought this troubling evidence to my Dad and he asked a very good question: "Are you sure it's oil?". Up to this point, I had assumed it was, not even thinking about the possibility that it might be grease.

Sure enough, it was grease. I removed the rear wheel to discover that the grease I had placed on the splines where the hub (MG# 12633200) meets the rear drive (MG# 12351400) was getting heated up and flinging out all over my rim. When I was indiscriminately slapping regular wheel bearing grease all over the splines, I had not anticipated this problem.

So, I cleaned up the mess and used Amsoil Fifth Wheel and Open Gear Compound. No more leaks and no more messy rear wheel!

Rear drive level plug

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As a rule, do not rely on level plugs. Measure the quantity needed, put it in, and be done with it.

On the Eldorado rear drives, Moto Guzzi placed the level plug in the incorrect location on some of the rear drives. Check out the photos below to see the difference.

Tom Christian sent me these photos, which were taken by Pete Roper.

Ralf Brinkmann sent me the following excellent photos of the original Guzzi fix for incorrectly drilling the level plug.

Rear drive ring nuts / lock nuts / spanner nuts / prong nuts / retaining nuts / lock rings

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Thanks to Tom Halchuk for sending me information on sourcing these parts.

On the V700 and Ambassador rear drives, a ring nut was used to secure the pinion bearings in place. Although it is easiest to simply upgrade to a hex nut, as is used on the later Eldorado rear drives, a ring nut can be used. The Whittet-Higgins Company manufactures ring nuts and special locking washers of the proper dimensions.

Original size: 25 mm x 1.5 mm
Whittet-Higgins Retaining nuts (KM-05 or KMM-05)
Whittet-Higgins Lock washers (MB-05 or MBA-05)

Rear drive seal cross-references

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Small seal located on the outer side of the rear drive as viewed from the perspective of the motorcycle.

38 mm ID x 50 mm OD x 7 mm Width

Large seal located on the inner side of the rear drive as viewed from the perspective of the motorcycle.

70 mm ID x 85 mm OD x 8 mm Width

Spline lube

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I've found that typical grease on any of the Guzzi splines (clutch input hub, drive shaft, u-joint, and rear wheel hub) simply heats up and flies off. This goes mostly without notice on everything except the rear wheel hub, where it spins out on the rim and tire making a mess of things.

That being said, I think it is important for these splines to be lubricated. If not, it is just metal working against metal and the result is a shorter life.

A while back, someone in the MGNOC newsletter suggested using Amsoil Fifth Wheel and Open Gear Compound. My experience has been very positive with this product and it has not spun out all over my rear wheel.
Contributed by Joe Jump on the old Topica Loopframe_Guzzi news group (which has now moved to Yahoo!) - I had a tube of the BMW red spline grease left over from my K-Bike days. Applied to my new hub, the splines in the flywheel, and to the splines in the friction plates using an old tooth brush. In 100 miles since finishing the job, no problems with fouling the clutch plates. Clutch engagement smooth as butter.
I think ol' Corntown used spray lithium grease on Creamsicle with no ill effects. I wouldn't worry too much about contamination of the plates, but I would try to select something that has a chance of staying in place.
Contributed by Chuck DeSantis on the old Topica Loopframe_Guzzi news group (which has now moved to Yahoo!) - Another option is Honda Moly 60 paste. I've used it on a bunch of different spline gears, even the rear wheel drive gear. Use sparingly so it doesn't fling; stays put and lasts a long time.
Contributed by Tom Halchuk in a personal email. In Tom's own words:

I mentioned to you a while ago of a coating a friend on mine has used before. It is a extremely hard dry lube. He is a prototype machinist. We coated a few shafts in a test. Then tried to machine the shafts. It was almost impossible unless we gouged the surface first with a punch.

I coated my spline early last year. The clutch pull with the coating on the spline is very smooth and consistent. I have about 4K and 15 months on the spline.

The name of the company that made this is TechLine Coatings (Part Number DFL-1. POWERKOTE DRY FILM LUBE). To apply the stuff you need to first sandblast the area with very fine aluminum oxide at 40 psi. Then apply the coating after mixing it very well with an electric drill or something. After this you then apply the material with an air brush to achieve an light but full and even coating. I found you can just paint it on as it seems to work just as well. After you let it air dry you then bake it in your wife or mothers oven for one hour at 350° F. After the part cools you then burnish the area with fine steel wool or even a fine wire wheel brush, this will leave what's left imbedded as part of the metal surface and does not seem to add to the dimensions. It seems to me that any metal that can stand up to being baked at 350° F would benefit.

U-joint carrier bearing cross-references

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The physical dimensions of the sealed carrier bearing (MG# 92204228) are as follows:

ID: 28 mm
OD: 58 mm
Width: 16 mm

Here are various cross-references:

Maryland Metric item no. 62/28 2RS
Consolidated 62/28 2RS
RIV ALN 28
FAG 62/28 2RS
GMN 62/28 2RS
KML 62/28 2RS
Koyo 62/28 2RS
NSK 62/28 DDU
SKF 62/28 2RS1
STEYR 62/28 2RS

U-joint carrier bearing removal

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I extracted this information from Doug (spudrekop) and Matt Moore off of the Yahoo! Loopframe_Guzzi newsgroup. In their own words:

Intial post...

Doug (spudrekop): Yesterday I had a few minutes to continue the stripping of the "Maroon Goon" and ran into a minor bump. The driveshaft support bearing is held in the swingarm with an internal circlip. The circlip was a BEAR to remove since the U-joint had been rubbing on the "ears" of the circlip, thus making my snap ring pliers somewhat ineffective. I did eventually get the circlip out, but now the bearing won't come out of the swingarm. Since there isn't a lip on the outer race, I don't want to tap too hard and risk botching up a good bearing, but in order to get the swingarm powder coated, this bearing has got to come out, No? Any help would be appreciated.

After numerous suggestions...

Doug (spudrekop): Thanks for all the suggestions. Bearing is still stuck, although it moved a little bit yesterday. Heated it up to the point that it took the old paint off. Yikes! Dropped an ice cube on the bearing and proceeded to pound on a socket/extension from the back side. This thing is really stuck. Would placing the entire swingarm in the freezer overnight, then heating it help? Would like to know how you folks get the swingarm bearing races out, too. I can get a small inside puller on, but not get enough power on it to pull the races.

Matt Moore: What I did was make a "puller" using a long bolt and washer(s), either the head of the bolt or combination of bolt head and washers where the shank was long enough) through a bar across the cup. I tightened the nut on the bolt, with put tension on the bearing. I then applied heat with a heat gun or propane torch (can't remember which) and continued tightening the bolt. It wouldn't budge this way, but then I used a long drift punch/socket extension and beat on it. It let go with a POP. As was prevously stated: Replace the bearing, it's cheap insurance.

Doug (spudrekop): Finally got the #%^!*'in' driveshaft carrier bearing out of the swingarm! Put the swingarm in the freezer (don't tell the queen) for 6 hrs. Rigged up a puller using a 1/2" X 12" carriage bolt. Then heated the outer surface of the swingarm until it was toasty. Put a 12" crescent wrench, with 4' breaker bar on the puller nut and gave it a yank...............POW! That sucker was out 'o there. Thanks for all the helpful tips.

U-joint carrier bearing removal: Aftermath with the bearing on the carriage bolt.U-joint carrier bearing removal: Aftermath with the bearing on the carriage bolt.

U-joint carrier bearing removal: The set up ready to go in the swingarm. I used two pieces of 1/4 inch plate steel to space the big socket at the swingarm hole, so I wouldn't be heating the whole rig.U-joint carrier bearing removal: The set up ready to go in the swingarm. I used two pieces of 1/4 inch plate steel to space the big socket at the swingarm hole, so I wouldn't be heating the whole rig.

Moto Guzzi Loop Frames - Rear drive & U-joint

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Rear drive / bevel box rebuilds