| All Trucks, Campers, Trailers, RV's and Motor Homes All Trucks Includes Pickup Trucks. All Tow-able Trailers, Camping Trailers, RV's, 5th Wheelers and Motor Homes, Etc. |  07-07-09, 10:04 AM | | Member | | Join Date: Jan 2009 Location: BC Posts: 6 | | | Differential repair
1989 GMC Van, 3/4 ton, 5.7 l (350 cu in) engine, conventional differential
Hi, I opened a differential because there was a whining noise when cruising at 80km/h. I found one of the pinion gears has a broken tooth and several others teeth are pitted. I took both pinion gears out, the other looks fine. I also checked the side gears (the ones driving the axels) they seems fine as well a crown gear. I phoned around and I was told by GMC dealer that they sell an o/h kit for $ 1,000.- but non is available across Canada! They suggested to ask an independent "rear end" supplier to get a pinion kit.
Do I have to replace all gears at once or is it ok to replace only the damaged one? Also do I have to adjust/shim some clearences? What to watch for?
Thanks for a reply! Danigo | 07-07-09, 11:06 AM |  | Topic Moderator | | Join Date: Jun 2008 Location: S.E. Texas Posts: 710 | | | If the gears are bad, yes you must replace both. They come as matched set.
It would be a better idea to take it to a rear end shop, not a dealer. An independent shop most of the time anyway, will do a better job at a lower price.imo
Travis | 07-07-09, 02:24 PM | | Member | | Join Date: Jan 2009 Location: BC Posts: 6 | | Quote: Originally Posted by waterwelldude  If the gears are bad, yes you must replace both. They come as matched set.
It would be a better idea to take it to a rear end shop, not a dealer. An independent shop most of the time anyway, will do a better job at a lower price.imo
Travis | Thanks a lot Travis! To take it to a shop is not an option since I took it appart already. The repair kit is comming tomorrow and I'll do it myself. Any clearences to watch for? Have a good day! Danigo | 07-07-09, 08:52 PM | | Topic Moderator | | Join Date: Jun 2008 Location: S.E. Texas Posts: 710 | | | There are some tools that would make the job last a lot longer.
The gap or backlash, between the ring and pinion is about .004 to .006. That is the amount of clearance between the two. It will be adjusted with shims on the outer most sides of the ring gear bearings. It should be some what close if you go back with the same gear ratio. They do very from gear to gear. If you change ratio, you may have to pick up some shims at a rear end shop.
A rough rule of thumb is to use a sheet of paper. If by running the paper between the two gears, if it cuts the paper, its too tight, if it leaves scratch marks and does not cut it. (It has to scratch the paper.) You are as close as you can get with out the proper tools.
Read the directions very close!! Take your time!!
Just a little to get you started.
Travis | 07-08-09, 06:18 AM |  | Super Moderator | | Join Date: Mar 2003 Location: Cinti, OH Posts: 6,032 | | Richmond Gear sells a video on doing a rearend gear change. Allthough I do 90% of my work on the hotrod I leave the rearend work to my garage guy. WELCOME TO RICHMOND GEAR __________________
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