Yeah, I just got my pinion seal replaced, these cars are known for it, and I guess it's normal.

 

Well, the service department confirmed that it was the pinion seals doing so they "replaced it". That is all the detail they gave me. I do know that from time to time GM will post issues on something called a Mechanics "Bulletin Board" about common issues and I asked if this pinion seal issue was on that Bulletin Board and they said No. So if it starts leaking again I will post that at a later date. Hopefully them replacing it will be good enough. Good luck!

 

Hey,

I got a question for all those who have had pinion seal leaks. I've noticed about 2-3 teaspoons of liquid has collected on my garage floor right under the rear differential when the vehicle is parked. Does anyone else experience this volume?

I got under the car to try and determine the source of the leak, but it was so dirty that I couldn't locate it. An interesting thing to note is that it looks like some type of liquid has sprayed up onto the exhaust right near where the drive shaft and differential connect. Does this happen when the pinion seal is bad?

Also, how much can I expect to pay to have this fixed at a dealership?

Thanks!
__________________
NewRave [Brian]
2000 SS Camaro Convertible

===== SLP Options =====
Hurst Short Throw Shifter
Cold Air Induction Box
Mass Airflow Sensor
Loudmouth Exhaust
Temperature Module
4.10 Gears

 

I had to replace mine a while ago. You could notice drops or even a puddle of liquid, just depends on how bad the leak is. If you've got more than a small amount, you might want to check your diff fluid level before driving too far.

Question for everyone:
My diff makes noise. A lot of noise. Is there a specific torque setting for the pinion yoke nut? If so, is it important enough that improper torque would make my rear diff louder than my LT's, ORY, TSP rumbler setup? Dammit, I hate not having $2500 for a 12-bolt!!

Also, can anyone answer once and for all: when using GM Synthetic Axle Lubricant SAE 75W-90 do you ALSO have to add the GM friction modifier/LSD additive? I have had 2 dealerships tell me NO, and a hundred other people tell me YES.

If neither of these things are my problem, then I believe my rear got messed up when some dumbass 16 year old girl in a Suburban played bumper cars with my baby. She did hit the right rear tire as well as the rest of the car on that corner.

Abe

 

Holy ancient thread, Batman!

If the oil leaks out onto the driveshaft or pinion, the rotation may cause the fluid to spray up in a horizontal pattern (from side to side under the car).

If you're getting any fluid on the ground near the differential, odds are that's where it's coming from. I have had no leaks at all since I posted this original thread back in 2003, so once they get it right it seems to hold for quite a while...

 

Proper pinion bearing preload is critical! That is why you can't just replace the pinion seal for a proper repair. Reason: there is a crush shim between the 2 pinion bearings. When the nut is torqued, it slowly crushes it till the bearings start to put pressure on their races. This starts to preload the bearings as they push harder against their races. It's not like front wheel bearings where you tighten them lightly with a wrench, then back off a bit, pinion bearings are actually squeezed.

Proper preload is ~ 24 in/lbs with new bearings, ~ 8 in/lbs with used, if memory serves. Been a while since I've done a diff.

Reason you can't just replace the seal: once you crush the shim, that's it. If you over crush it, you can't just back off, needs a new one, cause it's sprung. So the one that came in it from the factory can't just be reused. In order to put in a new one, you have to remove the posi carrier and pull out the pinion.

In order to properly do the preload setting, you have to install a new crush shim, install only the pinion gear, and torque nut till the slack is gone. Then you put a dial in/lb torque wrench on it to check preload. You alternately put more torque on it/check it, till you sneak up on proper preload setting. Then you reassemble the rest of the diff.

You can get away with just replacing the seal sometimes, but the possible consequences of doing it wrong include howling noises from the pinion bearing being over preloaded causing them to be destroyed, being under preloaded causing them to not be properly supported and failing, like an under torqued rod bolt.

Solid shims replace the crush shim. You pop it in there and torque it to a set value. Check the preload. Too much preload, and it needs a thicker shim, too little and it needs a thinner shim. The pinion gear needs to come out in order to do this.

 

Angel, thanks for you reply and info. "Howling". That is the exact word I would use to describe the noise my rear diff makes. Dammit.

Abe

 

Angel, thanks for your post--can you provide a little more clarification? I've read a lot of posts that recommend replacing just the pinion seal in order to fix a leak from the rear differential. Is it your opinion that even if this is done at a shop, it's the wrong approach?

Thanks for your help!

 

Keep your eyes peeled on the LSx boards for 12 bolts. They come up once in a while and you can save a few hundred. Board sponsers will sometimes sell them new for a couple hundred less on specials. Check the sponser sections of the boards.

As far as your lube question, I put just the synth lube when I replaced diff fluid, no additive. Valvoline I think. No chatter. There will be no possiblility of damaging anything if you don't use the friction modifier. If it chatters around corners, you can buy some and throw it in, if it doesn't chatter, no problem.

Heads up: when an axle gets hit (crash or slamming a curb) a lot of times it will lead to the infamous broken retaining bolt on the pinion (spider) gear shaft. This happens cause the force of the impact travels up the axle, the axle hits the pinion shaft, the shaft hits the little bolt and breaks it. A bear to get that broken little bolt out. Your axle might be bent too.

 

You can just have the seal replaced, but it's not the proper fix due to the need to preload the pinion bearings properly. It's a quick fix. You can get away with it, or you might trash the bearings. When I was a kid my dad did the quickie fix on our 57's diff. It crapped out about 3 months later. Those diffs have a drop out pumpkin, so a trip to the junkyard for a pumpkin out of a 61 and it was good to go. I still have the 57 btw.

A good shop with the necessary equipment can do the proper repair in a couple of hours. Jmo.... and every diff I've ever worked on, whether a seal or a gear change, turned out fine, no grenade action.

 

I had the dealer replace mine 3 times,each repair lasted about 6 months.3rd time they contacted Chevrolet & there is apparently a problem with some of the yokes that are causing the seals to wear & fail.They replaced the yoke & seal last time & it's been fine since,which was over 2 years ago.

 

For all you guys that have new seals leaking after a few hundred or thousand miles:

Check for a groove on the pinion yoke where the seal rides. I had a new seal leak something fierce and found the seal surface had a SLIGHT groove worn into it. I replaced the pinion yoke and seal and no more leak. It can also be speedy sleeved but you need the exact diameter of the pinion yoke seal surface to get the right size speedy sleeve. GM has the kit with new yoke and seal (updated double seal design) for about $100.

Also if you do it yourself use a sealer on the yoke splines during re-assembly. Gear lube can migrate out the splines and leak around the pinion nut.

Last note -- if you have a crush collar and zap the pinion nut on with an impact gun you can crush the sleeve too much and destroy your gear set-up. I can't remember the details of how to retighten a crush collared pinion nut as my 10-bolt had a solid spacer after the 2nd rebuild and the DTS 12-bolt came with a solid spacer set-up. Try a search on pinion seal leaks.