I have a 1970 1/2 Z28 and the rear end has a howl noise when the car is slowing down in gear. No noise as long as you are accelerating, but let off the gas and it howls, and the howl is consistant with the speed. You push in the clutch and it stops immediately. It has had some work done to it, I see the pinion seal has been replaced, could the nut on the pinion not been tightened enough for the crush sleave? I will be selling this second generation car, and want it in top condition for the new owner. If it takes a complete rebuild I will do it, but the noise sort of come on fairly fast. I have 3 first generation cars, and know you guys will still help, thanks!!!

You need to find a mechanic who knows how to set up a final drive. Pinion nut can usaully be removed to replace a seal IF you mark it first and put it back EXACTLY where it was.

However if it is put back on either too loose or too tight it can cause problems as you are describing. More likely is that some other parts were also replaced, such as bearings. There are shim packs to set up the side to side clearance of the ring gear and washer type shims to set the depth of the pinion gear. In my experience, very few mechanics can properly set up a rear end. You need the correct tools, and it absolutely cannot be done without using the yellow or white grease paint to check the tooth pattern. If that pattern is off, you will get a whine on accelleration, or as you have discovered, upon decelleration.

Bad news is, if it has been doing it for long, all the adjusment in the world by the world's best technician, will not fix it. You will have to spring for new gears.

Good luck with it.

Lynn

IMO, pinion nut is too tight. It will require replacement nut, crush sleeve, and another seal. Don't forget the oil.

They tightened the pinion nut too tight and changed the pinion depth. By doing so, a noise has developed on the coast side of the gear. The pinion drives the ring gear while driving, but during coasting the ring gear drives the pinion. Put your foot on the clutch and remove the load on the ring gear, the noise goes away. Usually once gears start making noise, they don't stop, even if clearances inside are reset properly. I would take it back to the shop that performed the service and tell them to fix it.

Well I also think it has something to do with the pinion, but I'm not sure that the nut is too tight. It could also be too loose, or the reason that the seal was replaced might be that a pinion bearing is bad and caused the leak to start with. You need to check the pinion by trying to move it up and down to see if it is loose. Have the transmission in neutral when you do this so that there is no pressure on the drive shaft. If the pinion moves in any direction other than rotation then the nut is too loose. Torque the nut to 150 foot pounds and drive the car. If the noise is still there then get ready to replace the pinion bearings, or more.

Thank you very much for all of your responses. The guys here are of a great help donating their opinions, have a good Christmas everyone!