Topica Loopframe_Guzzi Archive
 

Subject: RE: rear drive rebuild

Author: Greg Bender

Date: Feb 15, 2005, 4:11 PM

Post ID: 1718397377


Well, as you know, there are three locations to use the shims:

1. between the pinion bearings
2. between the end of the pinion gear and the first bearing
3. between the case and the flange cover

When I put in all new bearings in my 8/33 gearset for my Quota, I only
used additional shims between the two pinion bearings to set them up
properly. I was able to reuse the shims in the other locations (and thus
maintain the same ring/pinion engagement).

I believe that the bearings in my Quota rear drive went out for two
reasons at only 25,000 (with symptoms before):

1. I don't think the previous owner changed fluids as regularly as he
should have - either that or it was run dry at one point (maybe right
after it was shipped over? I don't know).
2. I think there was a tendency for the factory to set up the pinion
bearings too tight (perhaps in an attempt to quiet the drive down?)
especially on 8/33 gear sets. This is rumor only, I don't really know.

I do know that using the same shim set up (as original) between the
pinion bearings was not nearly enough. I had to add several more to get
it right. So far, since I've made the repairs (all new bearings and
checked/adjusted all shimming), my rear drive seems okay. The ring and
pinion were showing some wear (due to the trashed bearing bits getting
ground up by 'em) and I wonder how long the ring and pinion will last.
But, since a new ring and pinion set is significantly more expensive
than new bearings, I thought I'd give the bearing route a try first.

Well, that's enough of my ramblings for now...

Ray Hale wrote:
 
Greg,
Yep, it's all about the wallet aint it? This bike sat a long time, low
mileage. The fluid levels were up in the motor, trans and rear drive.
Got lucky, mostly. I'll call MG tomorrow. Just made my VISA payment
today. It figures. MG shows only two thicknesses for shims. Were you
able to make do with one of those?
Ray


Greg Bender wrote:
 
Hi Ray,

Rick and Gordon had lot's of shims the last time I checked, but I may
have run 'em dry on a couple. Worth a call, though. If you can't find
something, let me know and I'll dig through my stash.

As for bearings, as long as they look and feel good, then I wouldn't
worry about it. The pinion bearings are the cheapest to replace and also


the quickest to wear (in my experience), so give them the best look
over.

But, it sounds as if your box is in really good shape - that's great for


you and your wallet!

Ray Hale wrote:
 
Greg,
I'd already read and re-read your stuff and Pete's. Very helpful.
Thanks. The components are really straight forward in this rear box.
Nothing tricky it seems. Of course I've yet to attempt shimming but
right now it seems the really difficult part will be to obtain a variety



of shims. Not exactly standard fair.

I've taken good pics of everything as I disassembled this afternoon.
Will try to get them into a Powerpoint presentation and maybe my son
will post on his website for me. (hint, hint)

The pinion is 8 teeth and the crown is 37. I gather this is rather
standard. Any opinions here? I'd like to be able to cruise at 75-80 MPH,



2-up, with camping gear strapped on. The chromed case I am transplanting



everything into is an older case with the lower drain plug and smaller
sized lubrication vents inside. There is one small, hopefully
insignificant outside shape difference. Both boxes, the one on the bike
when I bought it, and the chrome one I purchased, have the same part #.

I will replace seals of course but not sure about bearings. They appear
and feel great. No signs of unusual wear on the pinion and crown teeth
or the bearing races. Probably silly to do this just for the chrome but
I was curious what was inside there anyway and find myself with nothing
but time on my hands for a while. Another mystery unraveled.
Ray
PS - I smell like old gear fluid. Might be sleeping in the den tonight.
Even the dog doesn't want to come close. Cats are curious, however.


Greg Bender wrote:
 
Hi Ray,

If you haven't already, I've put all of my very limited wisdom on this
subject on my website. See:

http://www.thisoldtractor.com/gtbender/loopframe.htm#Rear_drive_/_bevel_box_rebuilds






Ray Hale wrote:
 
Hi,
Well, I'm sequestered at home for two months now and decided to tear
apart the rear drive on the Eldo, as a project to keep from dying of
boredom. I will begin after lunch today. I have read the shop manual,
some stuff off various websites and it looks like shimming the pinion is





the critical event.

I visited Stan Friduss and Mike Myers (Myers Racing) briefly this
morning and with their encouragement decided to proceed. Stan's advice
was not to rely only on the dial indicator method of shimming but didn't





elaborate as he and Mike were on their way to pick up parts to rebuild
for Daytona. I'll share what I learn of course. I'm taking pics every
step of the way, also.

Any sage advice as I begin? I figure if I can do this, I'll tackle the
trans next. Ian says the rear drive is the final frontier. Ian...you and





Ed raise a mug or two in my direction will ya? I'm going in. Can't be
any worse than trying to line up (and keep 'em lined up) pushrods on an
old A10 beezer while putting the top end together. That's a thankless
task. Or changing a starter motor on a '61 Ford with a big V8, or trying





to find the rear spark plug on a Chrysler, or #3 on a 356 Porsche. The
list goes on.
Ray

pax sine tedio
73 Eldo "19"



Regards,

Greg Bender
1971 Ambassador
2000 Quota
http://www.thisoldtractor.com/gtbender



pax sine tedio
73 Eldo "19"



Regards,

Greg Bender
1971 Ambassador
2000 Quota
http://www.thisoldtractor.com/gtbender



pax sine tedio
73 Eldo "19"



Regards,

Greg Bender
1971 Ambassador
2000 Quota
http://www.thisoldtractor.com/gtbender

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