Swap in 9.25" Heavy half diff or leave stock 8.25"

[That90sKid]

Hey guys I just put a 6" RCD lift in my 1998 chev k 1500 half ton with 35" tires (Build thread coming soon !!! ) and I am going to re-gear it to 4.56s .

I'm running a 14 bolt semi floating rear end with 3.73s right now

But I'm trying to decide if I should just re gear my stock 8.25" front diff or it's worth it and easy enough to re-gear a 9.25" heavy half diff I have and swap it in instead ? The 9.25" front diff is out of 1998 "heavy half" so it has the 6 lug axels . it's a little more expensive to re gear the heavy half diff but that's minor details . I got quoted around 600 for all the parts I need to regear :Ring and pinions and master bearings/Installation kit. That's front AND back .

The truck is my daily driver but also my weekend mud truck

Opinions ? I'm thinking the bigger diff is a good idea !

 

[88GMCtruck]

To my knowledge, the F44 "heavy duty" suspension that K1500 trucks received did not have anything different about the differential. Only K2500 and K3500 recieved the 9.25" front diff.

 

[FastOrange]

To my knowledge, the F44 "heavy duty" suspension that K1500 trucks received did not have anything different about the differential. Only K2500 and K3500 recieved the 9.25" front diff.

your right, F44, only applied to the rear.

 

[great white]

Front diffs on GM ifs are 8.25 until you hit the 8600 GVWR trucks.

Unless someone had already swapped a 9.25 into the donor truck your "heavy half" is an 8.25.

Staring at it won't really tell you anything either, they're visually very similar:

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Problem is, no matter what you do you're dealing with an aluminum case, which is prone to deflection under heavy load. Deflection in the case = gear death. They will adsorb a fair bit of abuse though, there's sled pull Dmax's out there throwing down over 1000 hp through the drivetrain. Different type of loading from mud running and rock crawling, but they are surviving heavy loads...

However, good news is a 9.25 will swap into a 1500 chassis with a little shaving cutting and "encouragement".

But not worth it IMHO unless you want a limited slip in the front, which is only available for a 9.25.....8.25 gets left out in the cold by the aftermarket.

If I were to swap in a 9.25, I'd look to find one of the newer HD 3500 ones which are supposedly made from cast iron. I've yet to confirm that rumor personally though (haven't felt like crawling under one at the dealerships) and the pictures found on the net look like they may be different enough that "bolt in" are words that might not apply:

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[88GMCtruck]

In either case, the CV shafts are the weak point.

 

[That90sKid]

Ok thanks guys . I just assumed that the "heavy half" diff I have was a 9.25" , so maybe it is just a 8.25" . I'll have to check. One thing I do know for sure is that this "heavy half" diff definently has bigger axel tube, (I'm actually not sure what you call that tube that extends to where you bolt the cv to ) if that tells me anything ?

 

[94blu1500]

I thought its wasn't possible to swap the 9.25 into a 1/2 ton without a lift? What is involved in the swap if its possible?

 

[outalne94z71]

I thought its wasn't possible to swap the 9.25 into a 1/2 ton without a lift? What is involved in the swap if its possible?

the 8.25 cv shaft will not bolt up to a 9.25 and i'm 80% sure the 9.25 cv does not fit the 6 lug hub so even if you hack the diff to fit in place of the 8.25 there would still be those issues to tackle

 

[great white]

You can get it in there, but only if you're good with a plasma and a welder and don't mind spending lots of cash.

IMHO, if you want 2500 running gear up front sell the K1500 and buy a 2500.

I'm not trying to be flip, I'm being serious.

If you still want to forge ahead, grab a coffee and have a read: http://www.gmfullsize.com/forum/showthread.php?t=64681

 

[Pkiser0993]

Don't be such a bunch of Debbie Doubters.....have another read from my post.....my swap is complete...http://www.gmfullsize.com/forum/show...ght=pkiser0993 .....go to page 3