Front differential broken, possible replacements?

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Typhoon#1985

New member
My front diff went a while back and I need to get this damn thing back on the road.

I can rebuild it, but the kits I find are around $200 and I can't image a junkyard diff being more than that. Are there any other GM vehicles that use the same one, or similar?

I can't find too much info on this but would a diff out of a 1st gen Bravada work? Or the 4x4 S10's and Blazers? Or is the 4x4 actuated from the diff in those? I read something like that, I know nothing about 4x4's....

I know it has to be the same gear ratio, ours is a 3.42, right?

If there is another one that works I'd rather just buy it and save myself the time of a rebuild and probably save some money at the same time. Any thoughts?
 
C

Captain Morgan

Moderated User
Re: Front differential broken, possible replacements?

Typhoon#1985 said:
My front diff went a while back and I need to get this damn thing back on the road.

I can rebuild it, but the kits I find are around $200 and I can't image a junkyard diff being more than that. Are there any other GM vehicles that use the same one, or similar?

I can't find too much info on this but would a diff out of a 1st gen Bravada work? Or the 4x4 S10's and Blazers? Or is the 4x4 actuated from the diff in those? I read something like that, I know nothing about 4x4's....

I know it has to be the same gear ratio, ours is a 3.42, right?

If there is another one that works I'd rather just buy it and save myself the time of a rebuild and probably save some money at the same time. Any thoughts?
Click to expand...

Rebuilding them is a little more difficult than $200 in parts. From what people have said on here, its one of the most difficult diffs to setup correctly.

Having said that, yes, you can use one out of a 1st Gen Bravada or 4x4 truck.

If using the Bravada, it should be direct bolt in and the ratio is 3.42. A 3.73 ratio also existed in the Bravada, so make sure its the right one.

You can use a 4x4 front diff as well from a Blazer or Jimmy, however you will need to swap over the right side axle and tube (not difficult). Also, be aware of the 3.08 ratio on the 4x4's.

Local yards by me want anywhere from $150-$400 for a Jimmy/Blazer/Bravada depending on mileage. There is also a Syclone diff listed in NY, but they want $500 for it.

I would recomment hitting up Craigslist or eBay. I picked up a Typhoon front diff that was sort of local to me for $9.95 (guy was pissed, lol), but there are TONS of people parting out 4x4 S-Trucks on CL.
 
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Typhoon#1985

New member
Re: Front differential broken, possible replacements?

I read that they were tough, all the more reason to just replace it.

I have a u pull it yard fairly close and stuff is usually pretty cheap there, I hope so anyway.

Is there a way to find what vehicles had what ratio? I know how to spin it and find out but I don't really want to crawl under 7 different junkyard trucks and take stuff apart.

The passenger axle and tube is the only part that needs to be swapped? That's easy enough.
 
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bigmileage

Member
Re: Front differential broken, possible replacements?

You can use just about any 7.25 diff, you just need to know what changes; most importantly one axle is different. I've converted a few for people (non AWD) to make the front AWD.locked all the time so that the 4wd engages when the transfer case is locked - it's an easy way to eliminate the vacuum operation on a 4wd.

Look in the glove box, the three digit codes are there. 90% wiill have 3.42s, sometimes a 3.73. GM never used a 4.10 or 3.08 in a later model 4wd. Worst case count the teeth and do the math.
 
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SuicideSy

New member
Re: Front differential broken, possible replacements?

The RPO codes are listed in the glovebox, GU6 is the code for 3.42 ratio (GT4 is 3.73).
 
2_60b4u

2_60b4u

Looking for 12's
Re: Front differential broken, possible replacements?

I have a front diff that I picked up for a spare on my truck that I would be willing to let go for 175 + 100 (shipping and crate materials). 76k miles on it.
matt@timberlinenw.com
Syclone_Parts002.jpg
 
T

Typhoon#1985

New member
Re: Front differential broken, possible replacements?

bigmileage said:
You can use just about any 7.25 diff, you just need to know what changes; most importantly one axle is different. I've converted a few for people (non AWD) to make the front AWD.locked all the time so that the 4wd engages when the transfer case is locked - it's an easy way to eliminate the vacuum operation on a 4wd.

Look in the glove box, the three digit codes are there. 90% wiill have 3.42s, sometimes a 3.73. GM never used a 4.10 or 3.08 in a later model 4wd. Worst case count the teeth and do the math.
Click to expand...

So there is a system in the 4x4 ones to engage and disengage the front end, as opposed to ours which is all the time? And it's engaged by the vacuum system?
 
B

bigmileage

Member
Re: Front differential broken, possible replacements?

^^Correct. It's been a few years since I've done one, but it's more or less a different passenger side axle (going from memory here) that eliminates the engagement fork and gear plates. On a normal truck there is vacuum that pulls the fork and engages the axle. Simultaneously the transfer case is engaged. It's very common for the vacuum engagement (under the battery on regular trucks) plunger to fail. Most reliable way is to simply convert the front diff to awd an rely on the tcase to engage 4wd.
 
T

Typhoon#1985

New member
Re: Front differential broken, possible replacements?

bigmileage said:
^^Correct. It's been a few years since I've done one, but it's more or less a different passenger side axle (going from memory here) that eliminates the engagement fork and gear plates. On a normal truck there is vacuum that pulls the fork and engages the axle. Simultaneously the transfer case is engaged. It's very common for the vacuum engagement (under the battery on regular trucks) plunger to fail. Most reliable way is to simply convert the front diff to awd an rely on the tcase to engage 4wd.
Click to expand...

Ok so the engagement stuff is on the passenger axle and I just swap with my original and everything's cool?

I've never seen the 4x4 one, so I have no idea what they have different from ours.
 
C

Captain Morgan

Moderated User
Re: Front differential broken, possible replacements?

Typhoon#1985 said:
Ok so the engagement stuff is on the passenger axle and I just swap with my original and everything's cool?

I've never seen the 4x4 one, so I have no idea what they have different from ours.
Click to expand...
Yes, I said that in post #2. Its easy, 4 bolts and a little Ultra Grey and youre set. Tighten the bolts to 36 Ft. Lbs.

axletube.jpg
 
fivetodrive

fivetodrive

CRISPY
Re: Front differential broken, possible replacements?

John and I at Bully Racing offer rebuilt front differentials for the Syclone and Typhoon. Why take the risk with a used unit, Pricing for a stock rebuilt unit is $600. We also offer a torsen style limited slip option as an upgrade. You can call me at 720-933-7635 or email at aaronptimm@yahoo.com
 
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