GSI Differential - Transmission Forum

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GSI Differential
Friday, February 12, 2010 6:24 AM
i found someone with a gsi differential for a god price. Can i take the spider gears out of this and replace the ones in my 99 Sunfire GT isuzu trans? If not what would need to be replaced to cheange out the whole differential?

Re: GSI Differential
Friday, February 12, 2010 5:25 PM
I'm not the expert regarding these, but I believe you're SOL here, because teh GSi diffs don't fit our axles. You want a non-GSi tranny.





Re: GSI Differential
Saturday, February 13, 2010 9:40 PM
^ ^ ^ That's always been my understanding as well. On a side note, I miss my '92 Gsi.




Re: GSI Differential
Tuesday, February 16, 2010 7:00 PM
I don't know if the Z24/GT axles are any different than the base ones, but my LN2 axles fit right in the GSI differential with no issues. If you want to count the number of splines on yours, I can let you know if mine matches.

But, I have a feeling they are exactly the same. I know that I can use the SOHC Geo/ all other early 90s Isuzu differentials as well.
Re: GSI Differential
Saturday, February 20, 2010 7:53 AM
Well i went to autozone's website and both the 99 sunfire gt and the 99 cavalier z24 use the same part number for their axles.

Duralast
Driver side PN 9547
Passanger side PN 8580

So you are saying that your stock axles fit the gsi differential fine? I am not sure what LN2 axles are?
Re: GSI Differential
Saturday, February 20, 2010 3:34 PM
Wagonwes wrote:I don't know if the Z24/GT axles are any different than the base ones, but my LN2 axles fit right in the GSI differential with no issues. If you want to count the number of splines on yours, I can let you know if mine matches.

But, I have a feeling they are exactly the same. I know that I can use the SOHC Geo/ all other early 90s Isuzu differentials as well.
That's interesting. Yes, in fact, the J-body axles are all interchangeable. However, I have been told by guys who have built hybrids that the GSi diffs take different axles than the base models, but the ring gears will swap for use of the 4.11 gears in our tranny. Since I'm picking one up for the 4.11 anyway, I will have to try it in my tranny before I pick up the non-GSi tranny too.





Re: GSI Differential
Saturday, February 20, 2010 7:01 PM
Quiklilcav wrote:
Wagonwes wrote:I don't know if the Z24/GT axles are any different than the base ones, but my LN2 axles fit right in the GSI differential with no issues. If you want to count the number of splines on yours, I can let you know if mine matches.

But, I have a feeling they are exactly the same. I know that I can use the SOHC Geo/ all other early 90s Isuzu differentials as well.
That's interesting. Yes, in fact, the J-body axles are all interchangeable. However, I have been told by guys who have built hybrids that the GSi diffs take different axles than the base models, but the ring gears will swap for use of the 4.11 gears in our tranny. Since I'm picking one up for the 4.11 anyway, I will have to try it in my tranny before I pick up the non-GSi tranny too.


I can tell you with 100% certainty that the GSI differential will fit with our axles in our case, without machining or anything fancy. I have it in my car now, it works. I don't know if there is a difference between 90-94 GSI differentials, bit my 91 is indeed a 4.11 from a Storm, and my axles fit in it perfectly.
Re: GSI Differential
Sunday, February 21, 2010 7:24 AM
I just realized that I forgot to add that if you swap the diff, you must also swap the input and output shafts. The shift rails can stay, but the shafts must be swapped. You also have to swap some of the bearings from the Geo case to the Cavalier case. The Geo uses some tapered bearings where the Cavalier does not (for some things).
Re: GSI Differential
Sunday, February 21, 2010 5:48 PM
Yeah im not interested in swapping out the whole differential and changing the ratio to 4.11's. Im just looking to swap out the spider gears into my stock differential for a more reliable dd. I have already been through 2 trannys in a little more than 20,xxx mi (the original one and a junkyard replacement) and im sick of having to go to the junkyard and getting used replacements that in my mind are ticking time bombs. Knock on wood tthe one that i have in my car right now is going good until i can get the time and resources to break open one of my busted trannies and replace the spider gears.
Re: GSI Differential
Monday, February 22, 2010 6:22 AM
If you just swap the spiders, I believe you have to re-check the backlash in the gears. You can do it yourself but you will need a good dial indicator and some shims. If you are not up to it, a good rear axle/transmission shop should be able to do it for under 50 bucks or so if you bring them in the diff.
Re: GSI Differential
Monday, February 22, 2010 6:39 AM
I used a dial caliper to measure the thickness of the gears and shims. I got it as close as I could to what was in there (about .002 thinner) and never looked back.

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