Rear bevel drive seal replacement (small block)

[SED]

Thought this might be helpful.  And it will help me remember the next time I get into the bevel drive. ;)  Hope you find it useful.
I'm definitely inspired by photo essays of Chuck in Indiana  ;-T

You will need a small 2 or 3 jaw puller - otherwise pretty standard tools.

Problem-Gear oil from the rear drive was coating the drive side of the brake disk and dripping down the wheel when parked.  Seal (arrow S below) was leaking.


Put bike on center stand and secure it by looping a tie-down strap behind the stand and through the front wheel (or to your lift) - you'd hate to push the bike forward off the stand:


Remove top mount of rear shocks (allows the swing arm to move up and down giving access to rear axle).
Remove rear axle and rear wheel.
Remove 2 brake caliper mounting bolts.
I chose to remove the bevel box from the swingarm rather than mess with the boot between the swingarm and gearbox.  Loosen the 4 acorn nuts that join the bevel box to the swingarm and pull to the rear.  Note: the pinion bearing holder is pinched between the bevel box and the swingarm and could pull out or fall out.  Also there is a coupling, a spline adapter and a small spring that will probably slide out of the swingarm as the bevel box is removed.

This is quick.  The first picture below was taken at 6:02 and the second at 6:11.


9 minutes later:

[SED]

Next pull the rear shock off the bevel box.  Clamp the disk with soft jaws and remove the bolts that hold the disk.


Slide pinion shaft and bearings out of bevel box and wrap in a nice clean towel for safe keeping.


Remove axle spacer.  This one was stuck and had to be loosened by tapping from the side with a rubber hammer.

[SED]

Fold back the lock tabs and remove the 7 bolts that hold the back of the box from the aluminum housing.


The housing with the back removed.


Between the housing and back plate is a shim and some very thin gaskets (H & I below) that set the spacing between the ring and pinion.  I assumed that they were set correctly and did not disturb them.


Two things to check:  First that the nose of the housing has an oil passage that carries gear lube between the pinion bearings like this.  (hole near top of photo looking in the nose of the housing) If yours does not, Chuck from Indiana has a great photo tutorial of it here on WG.  This passage was drilled with Chuck's help.


Second, check that the bevel drive has Schnorr washers (1st picture) and does not have the "lock plates" (second picture).  Apparently the lock plates don't lock, and they are too thick to fold over as locking tabs and they have been known to allow the bolts to back out of the ring gear.


Bad "Lock Plates"

[SED]

Forgot to mention that when you pull the back of the bevel box off there is a roller bearing that may stay with the housing or come out with the back.  It is shown here:


Protect it with a clean rag.

Also there is a small seal (AB in the parts diagram above) that rides outside the bearing on the rusty nose at the top of the picture (arrow).  The seal is down in the housing and should be checked that it  is still in good condition.  

[SED]

There is a circlip that holds the inner race on the nose of the "hollow shaft".  (The hollow shaft holds the ring gear and the bearings that drive the rear wheel.  It is labeled D in the parts diagram above.)


The race may need to be driven onto the shaft more to expose the circlip.  Light tapping with a mild steel punch works.


Before pulling the inner race clean up the nose of the hollow shaft to make it easier for the inner race to come off - Arrow:


A small puller is probably the only special tool needed.  The jaws grab under the 2 washers below the inner race.  I was concerned the washers would be bent by the pull, but the inner race was not too tight on the hollow shaft.


Clamp the hollow shaft in the vice using soft jaws and remove the 6 ring gear bolts and their Schnorr washers.  They should be held in by locktite.

[sib]

Second, check that the bevel drive has Schnorr washers (1st picture) and does not have the "lock plates" (second picture).  Apparently the lock plates don't lock, and they are too thick to fold over as locking tabs and they have been known to allow the bolts to back out of the ring gear.

The parts manual blowup pic and the parts table for the '13 V7 series show neither Schnorr washers nor lock plates under the bolts.  The workshop manual mentions "safety plates" but none of the pics show them.  What gives?

[SED]

This is where I departed from the Guzzi workshop book:
Guzzi says tap out the hollow shaft with a plastic mallet - I think they mean Rubber mallet.  It didn't work.

Instead heat the bearing and back plate with a hairdryer  :wife:  then turn it over and bang the nose of the hollow shaft down on a nice block of wood.




And Bob's your uncle.

[SED]

The parts manual blowup pic and the parts table for the '13 V7 series show neither Schnorr washers nor lock plates under the bolts.  The workshop manual mentions "safety plates" but none of the pics show them.  What gives?

I should say that this is for a 1981 Monza.  I've read on WG that the lock plates were a problem and that Schnorr washers and lock tight the solution, but I don't know when Guzzi changed things.  They may be using just bolts and locktite now.

[SED]

Should also say what workshop manuals I'm referring to!
1983 V50III etc. from Gregory Bender's website:
http://www.thisoldtractor.com/mg_manuals/workshop_manual_v35-ii_v50-iii_v35-imola_v50-monza_v35c_v50c_v65_v65sp_en.pdf

And the 2003 Breva manual from Guzzitek:
http://www.guzzitek.org/gb/ma_us_uk/750/Breva750IE_042003_Atel(GB).pdf

Both sites are excellent resources - thanks to their owners!

[Chuck in Indiana]

Thanks for that, SED. Attaboy. ;-T We're beginning to get some small block stuff documented here. I wish someone would do the transmission..

[SED]

The seal presses into one side of the backplate and the bearing the other.  I tried to pry them apart like this and ended up scaring the aluminum backplate   :'(  so don't do this:

Perhaps you can put a drift through the bearing to drive out the seal (Guzzi says to drive out seal first), but the bearing ID is smaller than the seal ID.

I heated the backplate with the hairdryer  :wife: and bearing came out easy.  I used a sharpie to mark the bearing so it could be put back the same way.  This shows the backplate ready for the new seal.


BTW - the bearing (U in the parts diagram) is 70x110x13 16014 SKF and can be found on the internet for reasonable prices.  This is for an early '80s small block - don't know if the modern bikes are the same.

The cause of the seal failure was corrosion on the hollow shaft.

Cleaned up sealing surface with 400 grit wet or dry.

[SED]

Thanks for that, SED. Attaboy. ;-T We're beginning to get some small block stuff documented here. I wish someone would do the transmission..

Thanks Chuck.  Love your work.  And that Aero engine is cool!

[SED]

OK - gotta run some errands, so more pictures later.

Hope you like it so far.
Shawn

[Chuck in Indiana]

OK - gotta run some errands, so more pictures later.

Hope you like it so far.
Shawn

Absolutely. I found that if you use the hair dryer :wife: or industrial heat gun here, it takes very little to pull the race.

[SED]

So I cleaned all the parts.  (I use hot water and powdered laundry detergent for everything I can submerge)
Reassembly is reverse of disassembly according to Guzzi so I installed the seal and then heated the backplate and installed the bearing.  

Driving the seal into the backplate with large blocks of wood distributes the force so the large seal isn't dimpled.


Warm the backplate and push the bearing in the same way, then seated the outer race in the backplate with a soft punch.  Unfortunately I did not take pictures of most of the reassembly.

Pre-lube the bearing and sealing surfaces.

Warmed the bearing and backplate assembly with the :wife: and pushed the hollow shaft though the warm bearing with wooden blocks and seated the inner race on the hollow shaft with the soft punch.  No picture, but if you've been following along in the Breva workshop book you'll find an error at this step - the picture and instructions marked with the red arrow should be on the next page.


There is another interesting error: driving the hollow shaft into the bearing has a tendency to push the bearing back out of the back plate (there is no circlip holding it in) - so once you are sure the bearing is seated on the shaft, go back and make sure it is still seated in the backplate.  If not the hollow shaft will not turn easily when the backplate and bevel housing are bolted together again.

  

[SED]

Once the hollow shaft and bearing have been seated the next step is to reinstall the ring gear.  The recommendation has been to use locktite and Schnorr washers and torque to 40-42 Newton/meters.

Then install the two washers (larger first - P & O in the diagram) and inner race (M) onto the hollow shaft (I had to tap the inner race with a soft drift) followed by the circlip (L).


Pre-lube the roller bearing(N), small seal (AB) and ring gear and assemble the back plate to the housing with the shim (arrow I in diagram) and gaskets (H) between them.  I assumed the ring and pinion clearance was set correctly so did not change the shims or gaskets.


If the hollow shaft gets more difficult to turn as the bolts get tight it may mean that the hollow shaft is not seated in the bearing (U) or the bearing not seated in the backplate.

Re-insert the pinion into the bevel box making sure the oil holes in the pinion housing (L below) are aligned top and bottom when assembled on the bike.  Put the acorn nuts on the studs to keep it from accidentally dropping out  ::)  I installed the pinion before attaching the brake disk to minimize the chance of dirt entering the bevel box. 



Note that the nuts (T in top diagram) must be seated in their recesses in the backplate before the brake disk can be installed. 

Grease the coupling and spline adapter (L, M, N, O and P below) and make sure the little spring sits in the recess of driveline (C) and they bevel box should bolt right up.  Make sure the axle spacer is installed before installing the axle.  Dave Richardson suggests leaving the 4 nuts loose until the axle is installed and tightened so that it is aligned with the axle shaft.


Arrows show the spacers and gaskets in the installed drive.


Support the swingarm so that it is level and fill to the level plug with the appropriate lube. 


Bolt all the rest of the goodies together, check your tire pressure and go for a test ride. ;D

Hope this has been helpful.  And if you have any additional recommendations I'd love to hear them.
Shawn

[Mayor_of_BBQ]

Very nicely done! :clap


Sent from my iPhone using Tapatalk

[SED]

Absolutely. I found that if you use the hair dryer :wife: or industrial heat gun here, it takes very little to pull the race.

Thanks for the tip Chuck, wish I'd thought of it at the time, but it still came off without much trouble.

[SED]

Very nicely done! :clap
Sent from my iPhone using Tapatalk

Thanks Mayor!  I really have enjoyed your ambitious work on your V65 too - a great photo essay.  It's going to look sweet!  ;-T

[SED]

Went through and made a few edits for clarity and more info.

[Chuck in Indiana]

Went through and made a few edits for clarity and more info.

Most excellent, sir..  ;-T

[Guido Valvole]

Thanks much! I sent my Monza rear drive to Sean Fader when sparkly bits came out with the oil. It needed all new bearings, the pinion-lube fix, and correct shimming. That last was a bit daunting… where a Guzzi is just like a bevelhead Duck. Sean's done that a few times… I haven't. But the V50 needs the fix as preventative maintenance so great to have this reference.
cr

[sign216]

SED,
 great work! A valuable reference for the Guzzi community.   
Joe

[Antietam Classic Cycle]

Why wouldn't you replace the small seal at the same time?

[SED]

Why wouldn't you replace the small seal at the same time?

Well, next time I would! 

Other answers are that it wasn't leaking, I'm cheap and I didn't think about it!   :P

[SED]

Why wouldn't you replace the small seal at the same time?

Charlie's right, next time I would replace both seals and the large ball bearing.  Maybe also the smaller roller bearing.

But this brings up a question - If the large ball bearing is changed do the the ring and pinion clearances need to be adjusted? (re-shimmed?)

I would think you could use the same shims because the bearings will have almost exactly the same dimensions.  (it is easier to make a bearing with very precise dimensions than a ring and pinion set.)

But does anyone know?
Thanks!
Shawn

[SED]

Joe and CR - thanks for the compliments. 

Agreed - Sean Fader has a good reputation.  I considered sending this to him, but figured I could replace a seal.  Besides, I like learning new things!   :BEER:

[Chuck in Indiana]

Sean is as good as it gets.  Replacing the big bearing would have no bearing  ;D on ring and pinion fit. It'll be as close to the same as you can measure.

[Guido Valvole]

But that big bearing is $120 no matter where you get it. (cheap Guzzi content). Since there were bits of metal circulating through my Monza rear drive, all bearings and seals had to be replaced. ~ $300+ from a bearing supply house, all high-quality SKF, FAG, and such. No cheap Chinese junk. I *think* re-shimming is necessary only if the pinion bearings are replaced although shims H & I could be critical if they change the position of the crown gear relative to the pinion. The shimming procedure is covered in the shop manual. I thought about how much I'd save vs. how much it would cost if the rear drive failed at speed… and I'm as cheap as anyone.
cr

[SED]

;-T