9 Bolt Dilema
03-01-2024, 09:29 AM
#1
9 Bolt Dilema
Hi everyone! I'm fairly new to 3rd gens and especially the differences in rear ends. I have a 88 Iroc 5.7 auto car that is only a street driven cruiser. The car is all original but high mileage. I would like to rebuild my 9 bolt rear and keep the car numbers matching. It is a posi 2.77 gear ratio with disc brakes. The rear has a lot of slop and clunks very loudly when going in gear. I would like to rebuild and upgrade to a 3.23 gear ratio. For parts will I just need to get a new series 3 posi unit, gears and install kit? Is my 9 bolt considered a 7.5 or 7.625 in unit? I know I'll have easily $1500 into it but all the rears like Moser, Quick Performance, Hawks etc that I priced will run at least $3500 plus having to figure what to do for brakes since mine won't transfer over. Any help would be greatly appreciated. Thanks!
03-01-2024, 10:15 AM
#2
Re: 9 Bolt Dilema
3.23 isn't an option for 9-bolts, you'll have to go 3.27s. It'll be pricey no matter how you cut it. I would replace your U-joints before diving into the rear though. A clunk when going in gear is tell-tale for bad U-joints.
In terms of your parts listed, yes, that about covers it. You could consider doing 3.45s though since you're already in there, I don't know what your transmission situation is like. I have the 3.27 posi behind an SBC crate motor with a stock T-5 and it's about perfect for a cruiser.
In terms of your parts listed, yes, that about covers it. You could consider doing 3.45s though since you're already in there, I don't know what your transmission situation is like. I have the 3.27 posi behind an SBC crate motor with a stock T-5 and it's about perfect for a cruiser.
03-01-2024, 10:48 AM
#3
Re: 9 Bolt Dilema
3.23 isn't an option for 9-bolts, you'll have to go 3.27s. It'll be pricey no matter how you cut it. I would replace your U-joints before diving into the rear though. A clunk when going in gear is tell-tale for bad U-joints.
In terms of your parts listed, yes, that about covers it. You could consider doing 3.45s though since you're already in there, I don't know what your transmission situation is like. I have the 3.27 posi behind an SBC crate motor with a stock T-5 and it's about perfect for a cruiser.
In terms of your parts listed, yes, that about covers it. You could consider doing 3.45s though since you're already in there, I don't know what your transmission situation is like. I have the 3.27 posi behind an SBC crate motor with a stock T-5 and it's about perfect for a cruiser.
03-01-2024, 11:31 AM
#4
Re: 9 Bolt Dilema
Thanks for your response. I may look into the 3.45. If I buy from Summit, is there a brand that is better than most like Yukon, Motive, etc? If I go with all the stuff listed will I still use the factory posi cones? Also, I remember reading something about a crush sleeve eliminator?
03-01-2024, 12:49 PM
#5
Re: 9 Bolt Dilema
If I go with a new series 3 posi carrier say from Yukon will I still use the factory posi cones or are those specific to the factory 9 bolt posi unit only? Thanks for all your help.
03-01-2024, 01:25 PM
#7
Supreme Member
Re: 9 Bolt Dilema
the 9 bolt rear was made by Borg Warner Australia and is different design from the 10 bolt axle 7.75 ring gear.Seems there is a gear type posi similar to the Torsen posi found in 1998-02 4th gen 10 bolt axles.That type of posi ,along with 3.27 or 3.45 grears would be ideal 
Look around past threads and you will find imformation about the Torsen type posi carrier for the 9-bolt.
Look around past threads and you will find imformation about the Torsen type posi carrier for the 9-bolt. Trending Topics
03-01-2024, 01:32 PM
#8
Supreme Member
iTrader: (1)
Join Date: Sep 2005
Posts: 26,115
Received 1,688 Likes
on
1,283 Posts
Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: 9 Bolt Dilema
Since you have a 9-bolt, your options are somewhat limited.
Your play is probably the pinion bearings. So yeah, it's rebuild time, for sure.
The 9-bolt ring gear size is 7.75". 7.5" and 7.625" are the same thing, for all practical purposes, and are the numbers for the 10-bolt that also came in these cars. Nothing that fits inside the 10-bolt will fit your 9-bolt.
7.75" is NOT a 10-bolt size.
Since you have 2.77 gears now, that means you have a 2 series carrier. You can't put 3 series on it. The highest ratio you can use is 3.08, without replacing the carrier. AFAIK there are no "special" "thick" "adapter" gears available for the 9-bolt.
There are no "numbers" on your rear axle to "match". That's monkey-spank.
The same crush sleeve eliminator fits the 9-bolt that also fits something else. 8½" 10-bolt maybe, I forget. Butt it's available at least.
No, 9-bolt cones will not fit in a Yukon carrier. (if Yukon even makes one for the 9-bolt; not sure) You wouldn't need them in any case, since any posi carrier you buy, from whomever, comes with all its own internals. None of those interchange among mfrs except for the cross pin in some cases and the little bolt that holds that in.
Your 88 rear has the super crappy Delco-Moraine discs that never work. Yours probably don't either: if you don't believe me, put your rear up on jack stands under the axle tubes - under the axle tubes ONLY, NOT under the pumpkin, NOT under the frame, NOT NOT NOT NOT - then start the engine, put it in Drive, and see if you can stop the wheels with the brakes. I'm betting, not. There is NO SENSE WHATSOEVER in spending gigabucks "rebuilding" and "upgrading" a rear, and leaving that CRAP on there. The 89-up system is SO MUCH BETTER it's hard to believe; it will bolt right up to your rear, but you'll have to have THE WHOLE system, from backing plates outwards, which can be rather difficult to come up with. I would STRONGLY urge you to obtain that full system BEFORE tearing into your rear, lest you $$$$pend on gears and carriers and whatnot, and then discover your rear brakes STILL don't do anything at all.
Another issue frequently reported about that rear involves axle seals. For whyever, the 2 sides are different, and there is more than one version of them, I have no idea what the exact details of that are, like year models or whatever, on how to identify which version you have. One side of one version (the right side I think) is almost impossible to find. Make double damn sure you have THE RIGHT seals for YOUR rear BEFORE you tear it down, like maybe have BOTH versions on hand so that whichever you have you're prepared, otherwise you may find your car disabled for a REALLY long time, or that you just have to resign yourself to an axle seal that leaks.
Your play is probably the pinion bearings. So yeah, it's rebuild time, for sure.
The 9-bolt ring gear size is 7.75". 7.5" and 7.625" are the same thing, for all practical purposes, and are the numbers for the 10-bolt that also came in these cars. Nothing that fits inside the 10-bolt will fit your 9-bolt.
7.75" is NOT a 10-bolt size.
Since you have 2.77 gears now, that means you have a 2 series carrier. You can't put 3 series on it. The highest ratio you can use is 3.08, without replacing the carrier. AFAIK there are no "special" "thick" "adapter" gears available for the 9-bolt.
There are no "numbers" on your rear axle to "match". That's monkey-spank.
The same crush sleeve eliminator fits the 9-bolt that also fits something else. 8½" 10-bolt maybe, I forget. Butt it's available at least.
No, 9-bolt cones will not fit in a Yukon carrier. (if Yukon even makes one for the 9-bolt; not sure) You wouldn't need them in any case, since any posi carrier you buy, from whomever, comes with all its own internals. None of those interchange among mfrs except for the cross pin in some cases and the little bolt that holds that in.
Your 88 rear has the super crappy Delco-Moraine discs that never work. Yours probably don't either: if you don't believe me, put your rear up on jack stands under the axle tubes - under the axle tubes ONLY, NOT under the pumpkin, NOT under the frame, NOT NOT NOT NOT - then start the engine, put it in Drive, and see if you can stop the wheels with the brakes. I'm betting, not. There is NO SENSE WHATSOEVER in spending gigabucks "rebuilding" and "upgrading" a rear, and leaving that CRAP on there. The 89-up system is SO MUCH BETTER it's hard to believe; it will bolt right up to your rear, but you'll have to have THE WHOLE system, from backing plates outwards, which can be rather difficult to come up with. I would STRONGLY urge you to obtain that full system BEFORE tearing into your rear, lest you $$$$pend on gears and carriers and whatnot, and then discover your rear brakes STILL don't do anything at all.
Another issue frequently reported about that rear involves axle seals. For whyever, the 2 sides are different, and there is more than one version of them, I have no idea what the exact details of that are, like year models or whatever, on how to identify which version you have. One side of one version (the right side I think) is almost impossible to find. Make double damn sure you have THE RIGHT seals for YOUR rear BEFORE you tear it down, like maybe have BOTH versions on hand so that whichever you have you're prepared, otherwise you may find your car disabled for a REALLY long time, or that you just have to resign yourself to an axle seal that leaks.
03-02-2024, 01:02 PM
#10
Supreme Member
iTrader: (8)
Join Date: Oct 2001
Location: Il
Posts: 11,723
Received 773 Likes
on
520 Posts
Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: 9 Bolt Dilema
Between doing this and upgrading to 89-92 disc, you have a super nice rearend
https://www.thirdgen.org/forums/tran...sen-style.html
https://www.thirdgen.org/forums/tran...sen-style.html
03-04-2024, 06:56 AM
#11
Re: 9 Bolt Dilema
Since you have a 9-bolt, your options are somewhat limited.
Your play is probably the pinion bearings. So yeah, it's rebuild time, for sure.
The 9-bolt ring gear size is 7.75". 7.5" and 7.625" are the same thing, for all practical purposes, and are the numbers for the 10-bolt that also came in these cars. Nothing that fits inside the 10-bolt will fit your 9-bolt.
7.75" is NOT a 10-bolt size.
Since you have 2.77 gears now, that means you have a 2 series carrier. You can't put 3 series on it. The highest ratio you can use is 3.08, without replacing the carrier. AFAIK there are no "special" "thick" "adapter" gears available for the 9-bolt.
There are no "numbers" on your rear axle to "match". That's monkey-spank.
The same crush sleeve eliminator fits the 9-bolt that also fits something else. 8½" 10-bolt maybe, I forget. Butt it's available at least.
No, 9-bolt cones will not fit in a Yukon carrier. (if Yukon even makes one for the 9-bolt; not sure) You wouldn't need them in any case, since any posi carrier you buy, from whomever, comes with all its own internals. None of those interchange among mfrs except for the cross pin in some cases and the little bolt that holds that in.
Your 88 rear has the super crappy Delco-Moraine discs that never work. Yours probably don't either: if you don't believe me, put your rear up on jack stands under the axle tubes - under the axle tubes ONLY, NOT under the pumpkin, NOT under the frame, NOT NOT NOT NOT - then start the engine, put it in Drive, and see if you can stop the wheels with the brakes. I'm betting, not. There is NO SENSE WHATSOEVER in spending gigabucks "rebuilding" and "upgrading" a rear, and leaving that CRAP on there. The 89-up system is SO MUCH BETTER it's hard to believe; it will bolt right up to your rear, but you'll have to have THE WHOLE system, from backing plates outwards, which can be rather difficult to come up with. I would STRONGLY urge you to obtain that full system BEFORE tearing into your rear, lest you $$$$pend on gears and carriers and whatnot, and then discover your rear brakes STILL don't do anything at all.
Another issue frequently reported about that rear involves axle seals. For whyever, the 2 sides are different, and there is more than one version of them, I have no idea what the exact details of that are, like year models or whatever, on how to identify which version you have. One side of one version (the right side I think) is almost impossible to find. Make double damn sure you have THE RIGHT seals for YOUR rear BEFORE you tear it down, like maybe have BOTH versions on hand so that whichever you have you're prepared, otherwise you may find your car disabled for a REALLY long time, or that you just have to resign yourself to an axle seal that leaks.
Your play is probably the pinion bearings. So yeah, it's rebuild time, for sure.
The 9-bolt ring gear size is 7.75". 7.5" and 7.625" are the same thing, for all practical purposes, and are the numbers for the 10-bolt that also came in these cars. Nothing that fits inside the 10-bolt will fit your 9-bolt.
7.75" is NOT a 10-bolt size.
Since you have 2.77 gears now, that means you have a 2 series carrier. You can't put 3 series on it. The highest ratio you can use is 3.08, without replacing the carrier. AFAIK there are no "special" "thick" "adapter" gears available for the 9-bolt.
There are no "numbers" on your rear axle to "match". That's monkey-spank.
The same crush sleeve eliminator fits the 9-bolt that also fits something else. 8½" 10-bolt maybe, I forget. Butt it's available at least.
No, 9-bolt cones will not fit in a Yukon carrier. (if Yukon even makes one for the 9-bolt; not sure) You wouldn't need them in any case, since any posi carrier you buy, from whomever, comes with all its own internals. None of those interchange among mfrs except for the cross pin in some cases and the little bolt that holds that in.
Your 88 rear has the super crappy Delco-Moraine discs that never work. Yours probably don't either: if you don't believe me, put your rear up on jack stands under the axle tubes - under the axle tubes ONLY, NOT under the pumpkin, NOT under the frame, NOT NOT NOT NOT - then start the engine, put it in Drive, and see if you can stop the wheels with the brakes. I'm betting, not. There is NO SENSE WHATSOEVER in spending gigabucks "rebuilding" and "upgrading" a rear, and leaving that CRAP on there. The 89-up system is SO MUCH BETTER it's hard to believe; it will bolt right up to your rear, but you'll have to have THE WHOLE system, from backing plates outwards, which can be rather difficult to come up with. I would STRONGLY urge you to obtain that full system BEFORE tearing into your rear, lest you $$$$pend on gears and carriers and whatnot, and then discover your rear brakes STILL don't do anything at all.
Another issue frequently reported about that rear involves axle seals. For whyever, the 2 sides are different, and there is more than one version of them, I have no idea what the exact details of that are, like year models or whatever, on how to identify which version you have. One side of one version (the right side I think) is almost impossible to find. Make double damn sure you have THE RIGHT seals for YOUR rear BEFORE you tear it down, like maybe have BOTH versions on hand so that whichever you have you're prepared, otherwise you may find your car disabled for a REALLY long time, or that you just have to resign yourself to an axle seal that leaks.
03-04-2024, 02:07 PM
#14
Supreme Member
iTrader: (2)
Join Date: Apr 2000
Location: South Windsor, CT
Posts: 1,264
Likes: 0
Received 212 Likes
on
178 Posts
Car: '89 GTA
Engine: ZZ6TPI
Transmission: T56
Axle/Gears: Borg Warner 3.70:1
Re: 9 Bolt Dilema
Yes, I would rebuild the 92' rear end, especially if its a disc brake rear. The 92' would be a 7.625" GM 10-bolt and will be much easier and less expensive to get parts than the Borg Warner 9-Bolt. Plus, as sofa mentioned, the 89-92 rear disc brake setup is far better than the 82'-88'.
The 9-bolt is a very good rear end and I rebuilt mine on my 89', but parts were hard to come by and expensive. I sourced most of the parts from Australia. Not sure I would go down that same path again.
The 9-bolt is a very good rear end and I rebuilt mine on my 89', but parts were hard to come by and expensive. I sourced most of the parts from Australia. Not sure I would go down that same path again.
Thread
Thread Starter
Forum
Replies
Last Post