Just a question...

[B2k4E]

I think tonight my father and I are finally going to get to jack up my 86 Z28 and see whats up with the rear end. But just for laughs, the main thing causing us to do this is that every time I'm driving it and I start to slow down (get to around 16-20 mph) I start hearing a continious clank when I let off the gas or apply the brake. It also makes the same clank when it switches from second when slowing down, (about the same speed as mentioned above) except only once. When I accelerate or it upshifts into 2nd it doesnt make any noise. Seems like there's nothing wrong with it whenever I'm cruising above 35mph tho. No whines or hums of any sorts.

My father checked for slack in the driveshaft but he said that it didnt have enough in it for it to be the pinion bearing or u-joints. (What he originally expected) We saw while we were under it that it had a pretty good leak of fluid coming out of the pinion seal so we're replacing that. He's just wondering if that's all it is and it's clanking around from lack of and/or old rear end oil. It's still leaking too, when we brought it home from a 2 hour trip on the trailer it had a good 13" long by 3" wide puddle right where the seal would be.

Also should note my friend was riding with me once, he heard it and said "ya, my truck was making that same sound for a while before the ring gear shot out of it". But one thing to note was that when his rear end in his truck exploded, there was very little grease around where the ring gear made a cut in the plate when it shot out. (He sent me a pic an hour or so after it happened.)

My question is what do you suspect it is and if youve solved it what was it?

Hoping it's just the seal and lack of fluid. Really dont feel like buying new gears or getting the pinion bearing repacked.

There's a question poll above.

[GRASSHOPPER]

clanging to me means metal on metal, but open it up and look it over
make sure to check that the vent tube is not plugged or you will get to much pressure build up and blow out your new seals

good luck

[ron10]

i had a car do this once and trrned out to be the wrong oil in rear end.it would sound like the whole rear end was coning out of the car.

[B2k4E]

Being that it was owned by some cholo gangster looking guy. I wouldnt doubt if the wrong oil is in it. Said it had a 383 stroker in it, but my dad and I are agreeing that it looks an aweful lot like a 305 TPI... Idk tho, he put the record of him buying and having a used 350 TPI bored over to a 383 for $3500 and the tranny being rebuilt for about $500 I think; but thats another story/problem. The radio also seems to be wired into the courtesy curcuit instead of the radio circuit. There was a small draw on the battery so we started pulling fuses in and out. Pulling the CTSY fuse seemed to solve it. There was also a 25 amp fuse in there instead of a 20 amp fuse... seems mighty suspicious. Also found 11 small light bulbs in the console. showed them to my dad and he said they were dash lights that belonged in the warning slots in the cluster... sounds like he might have been hiding a few problems from me...

[MAC]

can you feel the clank when it happens? and is it a continuous clanking? like, clank clank clunk?...when coming to a stop?
also, test to see if it occurs when switching to neutral - rolling stop; prior to allowing it to downshift.
and, from under the car?..correct?
this was happening on my 87 5.7, turned out to be the Torque Arm Bushing, Aka Torshion Bar bushing. cost about $65? from chevy dealer. autozone, kragen, nor napa, had the part in stock nor recognized it existed. once I had the part replaced, no more clunking ^.^
the bushing is located under the car, right next to the driveshaft.

[B2k4E]

Well, looks like the rear end isnt going to explode after all. Popped open the cover today and no metal chunks or excessive wear. In fact, it's very surprising how theres not that much wear for a +20 year old drivetrain. Gear teeth and bearings were fine and there was still a pretty good amount of grease in it. The U-joints also had minimum wear too, found that out by further examining them by disconnecting the driveshaft from the rear end. Looks like a new pinion seal is the only thing in order for the rear end. Well, that and getting a set of 3.73 gears to replace the stock gears in it with something a little more capable to fairly quick starts and good cruising.

Originally Posted by MAC

can you feel the clank when it happens? and is it a continuous clanking? like, clank clank clunk?...when coming to a stop?
also, test to see if it occurs when switching to neutral - rolling stop; prior to allowing it to downshift.
and, from under the car?..correct?
this was happening on my 87 5.7, turned out to be the Torque Arm Bushing, Aka Torshion Bar bushing. cost about $65? from chevy dealer. autozone, kragen, nor napa, had the part in stock nor recognized it existed. once I had the part replaced, no more clunking ^.^
the bushing is located under the car, right next to the driveshaft.

I'm guessing your talking about that arm that goes from the tranny and bolts to the top and bottom of the rear end? We think it might be that cause the one in it seems to float there. It's either that or something quite a bit more expensive, but slightly expected for the THM700 R4 tranny, (whats in mine) the torque converter might be out of balance. Hoping its that arm, cause I dont have $500 - $800 for a new torque converter...

Want to fix the radio circuit after this so I can get some 80's music going. I know, I'm a senior in high school that secretly wants to live in miami during the 80's with a camaro...

[B2k4E]

Originally Posted by ron10

i had a car do this once and trrned out to be the wrong oil in rear end.it would sound like the whole rear end was coning out of the car.

Sorry for the double post, but does yours have a positrak rear end? I asked my father about that and he said that can happen if you use the wrong oil in a posi rear end.

[MAC]

Here's a couple *Before* pics, of the Torque Arm Bushing to which I'm referring to:

[B2k4E]

Originally Posted by MAC

Here's a couple *Before* pics, of the Torque Arm Bushing to which I'm referring to:

Ya, mine almost looks just like that. (except without the large crack) Quick question tho, is there supposed to be any rubber on the top of the bushing? It looks like there is supposed to be some rubber there. Also when we went to change the seal we found that something caused a sharp ridge on the yoke that the driveshaft connects to. We think that caused the original seal to blow out so we now are in need of a new one.

[MAC]

yes there's supposed to be rubber material surrounding the arm. two separate metal pieces that have rubber molding attached that compress the arm to keep it in place.
supposedly it's possible to get polyurethane as opposed to the standard rubber parts.

[MAC]

I'll take a couple *After* pix later on.

[B2k4E]

Ya, it's the torque arm bushing. Looks exactly like in your before pics. Put a peice of heater hose for a temporary barrier until I get a new one.

Originally Posted by MAC

I'll take a couple *After* pix later on.

Finished with rear end work. The gears in the rear end were actually very good for a +20 year old car. Looked like it had only about 10 or 13 years of wear. The gears need to be changed tho just because the ones that are in it are slightly to small of a ratio. Need some good 3.73 gears to replace the 2.37 gears. the seal was ripped because of a sharp ridge on the pinion yoke. Went to my donor car and robbed its yoke. Now the only things it needs is the rear brakes adjusted,torque arm bushing, a little bit of interior work, and a new paintjob.