Rear End Trouble Need help now !!!

[ModernMuscleHead]

I'm wondering if anyone has an Idea of what this can be. My 88 Formula 350 was leaking rear fluid. I took it to a licensed reputable shop that changed the rear pinion seal. Later that day I trounced the gas and got a load thud and I can feel something is not right in the passenger side rear. If I'm rolling and hit it the car goes fine and it goes fine down the highway. It only happens when taking off at half throttle or more, or when rolling slowly and it downshifts from 2nd to 1st. Anybody got a clue what this is ? Someone said its the posi unit and I'm wondering if they forgot to add the friction modifier.

[Jeff_in_Atl]

I've got to ask this even though you say it's coming from the rear of the car, it sounds a little like the transmission mount might have broken.

[ModernMuscleHead]

I've got to ask this even though you say it's coming from the rear of the car, it sounds a little like the transmission mount might have broken.

That is a good question. Someone told me that might be what it is. Would that be where the torque arm attaches ????

[Jeff_in_Atl]

No but in that area. It's between the transmission and the bracket that goes to the frame at the rear of the transmission.

[ModernMuscleHead]

Thanks. I will have that looked at too. I'm supposed to have it looked at on Saturday. I'm just trying to get an idea going in so I have something to go on.

[ConElite]

I second the Trans mount.

[Jeff_in_Atl]

One thing is if it is broken don't bother getting one from the local auto parts place. You'll break it within 6 months. I would suggest an Energy Suspension mount. They actually carry them at the Auto Zone stores around here. Don't get the prothane mount. They are notorious for being so hard that they transfer engine noises to the frame. I actually have one you can have but you won't want it. Maybe I can use it on my lawnmower somewhere.

[ModernMuscleHead]

Thanks for the info. I hope thats all it is. Much cheaper fix than a bad posi unit or something of that nature. I just bought the car a month ago and I know it needs to be strengthened in a few areas. It had some mods done to the engine and trans and its pretty fast for a 3rd gen L98. I ran my cousins LT1 6 speed Formula from a 60 roll and pulled away and I know L98 cars shouldn't do that to LT1's. It has long tubes, no cat, 3" exhaust, and aluminum driveshaft and a 1LE air conditioning eliminator. Thats just the stuff I can see. I'm not sure what else it has. The body and floors are unbelievably solid and it had new shocks, struts, brakes, tires and battery when I gave 3k for it so I don't think I did bad.

[MN6WS6]

I sincerely hope they knew the proper procedure for changing out that pinion seal. I have had pinion seals changed, and each time the rearend blew up about 250 miles later. These shops take the nut off and put it back on with an impact and just hammer down on it. Unfortunately, this crushes the sleeve that keeps the correct spacing and load on the inner and outer pinion bearings, which causes excess friction, and bye-bye bearings.

The correct way to do this is to literally tear the entire rearend down and re-torque everything to proper specs.

The redneck way (which usually works) is to count the exposed threads and make a mark on the pinion nut and on the pinion itself, then remove it, replace the seal, then reinstall it in the exact same location as it came off. This doesn't always work, but it's the only way to do it without a complete teardown.

The general rule is that if you have a 10 bolt GM rearend, regardless of what it's in, it is GOING TO LEAK out of the pinion seal. You just put fluid in it and live with it until something else fails in the rearend. It's just not worth the risk.

[Joe 1320]

I sincerely hope they knew the proper procedure for changing out that pinion seal. I have had pinion seals changed, and each time the rearend blew up about 250 miles later. These shops take the nut off and put it back on with an impact and just hammer down on it. Unfortunately, this crushes the sleeve that keeps the correct spacing and load on the inner and outer pinion bearings, which causes excess friction, and bye-bye bearings.

The correct way to do this is to literally tear the entire rearend down and re-torque everything to proper specs.

The redneck way (which usually works) is to count the exposed threads and make a mark on the pinion nut and on the pinion itself, then remove it, replace the seal, then reinstall it in the exact same location as it came off. This doesn't always work, but it's the only way to do it without a complete teardown.

The general rule is that if you have a 10 bolt GM rearend, regardless of what it's in, it is GOING TO LEAK out of the pinion seal. You just put fluid in it and live with it until something else fails in the rearend. It's just not worth the risk.

i was thinking the same thing. Too many times the pinion seal gets changed and boom!

[Trash man]

i kno this isnt an approved method but i have done it atleast 10 times and nothing has ever broken for me but it could be luck. but if you listen carefully u can hear a change in pitch from the impact gun but i dont recommend doing it if ur not comfortable

[ModernMuscleHead]

I got the rear checked today and it was the Trans Mount just like you guys said. As for the Pinion seal, I'm certain they probably didn't do it right. My cousin is an ASE master tech and he told me there are only about 3 guys in Michigan that know how to do it right and he's one of them. I plan to have him do the whole thing next weekend with new bearings, crush sleeve, axle seals, etc. Until then I'm going to drive it just once to a weekly cruise my club puts on so it should be okay.