I was driving my manual trans. 88 iroc 305, 9 bolt rear (i think 2.73). in 5th gear doing about 60mph I started to get a funny burning smell. When I I downshifted from 5th gear to pay toll I tried to take off from 1st the car started bucking and I hear a metal "clanking" sound. I pulled over and put the car in neutral and got out I tried to roll the car and it locked up. It would roll a foot in either direction but would stop. With the car running I can shift through all the gears even reverse but when I try to roll I reach a point where the car gets stuck and rolls back.
I figured it wasnt a problem in the transmission because the car wont even roll in neutral. I think the problem is in the rear end but I'm not familliar with it. Has anyone had this problem. What would it take to take off the differential cover and replace whatever is in there. I've had the car for a year and I have checked the gear oil could that be my problem?
Thanks for anyhelp

 

Sounds like you broke a few teeth off the ring gear....don't ask me I how I know. Pull off the diff cover and see.

 

Thanks I'm gonna pull it off today and have a look see.
Where would I buy a new one?

 

I pulled the diff cover and not 1 drop of oil came out. And that burning smell I smelled just before it broke down was trapped indide the diff cover. I cant tell if there is anything broken. I still a newbie, where do I go from here? What should I look for?

 

If it was run dry, you have problems. Path of least resistance is likely to hit a junkyard and pick up a used rear end complete from a compatible 3rd gen. If you have disc brakes now, find a disc brake rear...if you're drum brakes, find a drum rear (pretty easy).

The swap can likely be done using a Chilton's as a reference for the bolt torques, brake removal/installation, etc. If you want to hold out for someone to type up a rear swap procedure, go for it.

If you really want to have this rear diff fixed, you can have the car towed to a shop, or remove the rear and take it there. Much more $$ likely involved than a junkyard piece, given it was run dry.

 

Thank you I'll look into the junkard rears. but I want to make sure thats the problem before I start buying parts. I took a look at the driveshaft and from the transmission the driveshaft was pushed out about an inch. Could the tranny kicked the driveshaft back and cause my problem? Thank you for your help

 

An easy way to isolate the problem is to remove the driveshaft from the rear end yoke...if the rear wheels still won't move, the rear end is toast. If they move freely your trans is suspect.

Given no gear lube was present in the rear diff, it's highly suspect.

 

I took off the driveshaft and with the engine running I went through all the gears 1-5 and R and they were al smooth. I called GMSports.com and they said a rear end 2.73 with disc brakes was around $450 is that a good figure? How can I tell If I just broke a few teeth on the ring gear, or damaged the differential?And how easy would that be to replace? Thanks for any help

 

no. that is not a good price. you can get an ls1 rear for that money.

 

By way of comparison, the local yard here in NJ gets $150 for a complete rear end, any car/truck in inventory.

Looking down the hole of repairing your current rear...it's likely beyond your capabilities. I build engines, and rear-end work is beyond my capabilities, so don't feel like I'm trashing you.

And then there's the matter of the cost of 9-bolt rear parts, much higher than 10-bolt equivalents.

If you're looking for the cheap path, it doesn't get much lower than buying a complete used rear from a junkyard (shop around) and swapping it in yourself. Even $200 is cheaper than the labor bill alone for a gear/diff swap at a decent shop.

 

Thank you once again. I have a 9 bolt with disc brakes and I think the gear is 2.73. Could I get a different ratio? Would it make my car perform better. If you were in my situation what would be a step up from my setup, without making other modification? would it be worth it. Thanks in advance

 

If it were me, I'd hold out for a 10-bolt rear w/ disc brakes from a '90-92 F-car. Cheaper and more plentiful parts including gears, posi, axles, and bearings.

I'd go for a 3.42 gear set, and an Auburn or Torsen posi. Do a search on these here and you'll find good info.

 

if you do indeed have a 9-bolt you then have one of the following...a 2.77, 3.08, 3.27, or a 3.45 rearend ratio. as metioned above. kevinc hit the nail on the head. it would cheaper to get a 10 bolt disc rear end out of 89-02 f-body and install it.

 

Sorry guys I was being lazy. I cleaned off the tag on the differential the read "SPIN RESISTANT DIFF" the other read "p/n10046603 Ratio 3-45 ser no. 7678"
The tags agree with the RPO codes.
I called the salvage yards in my area and the cheapest I found was $300 and theres no difference in price between a 9 and 10 bolt. I would rather replace it with the original parts if I can find them. If I were in the junkyard how would I know if the rear end had posi, could I assume most 9 bolts with discs are posi? Or if the differential doesnt have a tag its not posi, if I take the diff cover off what would I be looking for to determine if it is posi?. Thank you again for taking the time to help me.