Hello,

I own an '88 GTA with the 305. I recently broke a tooth on the pinion gear and had to have my gears replaced. My mechanic was installing a new set of gears(342's) and ran into a problem. He tells me that the inner pinion bearing that came with the bearings/seals kit does not fit properly with the gears. He says it is either too big, or too fat and the crush sleeve will not properly engage. He tells me he does not know what the proper bearing is, and has no way to find out.

Can anyone here help me out?? I am at my wits end as he has it all torn apart, and refuses to do the work unless I can locate the correct bearing. He says it must be a rare part, because the one he tried should fit.

Thanks.

First: Is it a 9-bolt or a 10-bolt?

If it's a 10-bolt, there's only one "tail" bearing (the one that goes on right behind the yoke) that has been used in all 7½" 10-bolts since they came out (78?); but there have been 2 head bearings (the one that goes onto the gear with the shim behind it). They changed in about 81. You may have a kit for the early style, in which case the bearing won't fit in the housing, it will be so much smaller it might even fall through. NAPA carries it; it comes as a cone and a race. The race is the piece that goes in the housing, the cone is the piece that goes on the gear.

If it's a 9-bolt, I have no idea what's going on, as those are all the same AFAIK.

Tell us the part # of the kit you have, and it shouldn't be too hard to figure out what you need to get.

OBTW... part #s are HM82910 race, HM89249 cone for the newer ones.

double post

Thanks for the help so far. I appreciate it.

Ok, here is all the information I have. Please try to help me if you can.

1988 GTA, Auto, 305

It is a 10 bolt. When the mechanic took it apart he tells me that the gear ratio was 3.23 and that they are 7 5/8". So when he matched the new gears(used) with the old ones, he used the same dimensions as the gears that he found in there, except a different ration(3.42). So then he went to install them, and it turns out that the inner pinion bearing that he has is too fat. He verified with me on the phone just now that he had the correct kit(the new one).

He is not sure what is going on, as he states that this bearing is the correct bearing. He believes that he may have the wrong gears, but says he matched them exactly with the old ones I had. I have no idea if the gears had ever been worked on before, but my mechanic tells me that there is a chance that they were, and that the wrong gears were put in. The problem is that it shouldn't have lasted for the 5 years i've had the car(50k miles). I had thought the gears were stock at 3.23.

I checked the database here, and it says my car came in both 2.73 and 3.23 for auto, but I don't know how to tell which one mine had originally.

Also, my mechanic said to ask if 7 5/8" is correct, and what anyone knows about 7 3/4". He thinks maybe 7 3/4" are supposed to be on the car.

7¾" is the diameter usually given for the 9-bolt. You don't have that. 7½" and 7-5/8" are the 10-bolt sizes, they are really the same thing, that # is the outer diameter of the ring and has nothing to do with the bearings.

There's only one inner diameter of pinion gear. Can you get a pic of all the parts you have, and post it? Also post the part # of the kit you have, and/or the part #s on all the bearings, or show them in a pic. That would help identify what to do.

I am unable to get any pictures. I thought I could borrow a digital camera from someone but I wasn't able to.

My problem still exists.

The mechanic has quadruple checked everything. He has the correct bearings, and he has checked them numerous times. He has matched the gears EXACTLY from what was in there. Yet, the inner pinion bearing does not fit properly. I know it sounds crazy, and there must be something obvious we are missing. He says that he did work on an older Camaro once(think he said '84) and ran into a similiar problem in which he needed a special bearing. He does not remember a part number or how to reach this guy.

I do not know if this rearend has been worked on, or if was completely replaced at some point in the past. Any kind of information that is on there to tell me is rusted away. The only thing he can see on the axle is something to the effect of '84.

If anyone has any information, please help me. I am at my wits end. My mechanic actually specializes in gears, and he is almost embarassed to admit he can't figure it out.

He told me to ask if anyone knows of a TRANSAM Gear specialty shop, anywhere in the USA that he personally can call to explain the problem and try to get an answer. So if anyone here knows someone that we can call I would appreciate it.

Thanks alot.

There is no special bearing. There is no special gear. There is no difference between a Camaro / Firebird rear end and any other body style with the 7½" rear, or between 84 and 88, as far as the bearings are concerned. The only difference among bearings is that there is a 80-back version and a 81-up version; but the inner diameters of everything there is the same, the difference is the outer diameter of the head (rear) pinion bearing. There is no need for a Trans Am specialty gear shop, as there is nothing unique about a Trans Am; regular Firebirds, all the Camaros, the G body people, the S truck people, etc. all have exactly the same parts inside the rear end as our cars have (except of course for the F cars that have 9-bolts).

Post the part numbers. We cannot help you without some info as to what you have in your hand. We can guess all day long at why it won't go together, but without part numbers, they're not even educated guesses, we'd just be stabbing in the dark.

Post the part numbers of everything you have: the gears, the kit, the numbers on the side of the bearings (both the cone and the race), and any other part numbers you can find.

The bearing is a fairly tight, but not impossible, press fit onto the gear. I do them myself in my garage.

Make sure you have a 10-bolt, not a 9-bolt. I can't imagine anybody confusing them, but you never know... count the cover bolts.

Double post again. Damn laptop.

Thanks again for the response. It is definately a 10 bolt.

Here are all the part numbers:

OLD GEARS - PINION (broke)
14085343-13-42-GM 7 5/8"

NEW GEARS - PINION
14085344-12-41-GM 7 5/8"

NEW BEARINGS
- Inner Pinion HM89249
- Race for inner pinion HM89210
- Outer Pinion M86649
- Race of outer pinion M86610