8.5 GM Axle strength

[Anubis]

Any turbo LS guys out there running the stock 8.5 rear axle? My 5.3 is ready to go but I haven’t done the swap yet. I’m planning for low boost to keep things reliable so expect around 600 hp at the wheel. I really don’t want to swap rear ends….

 

[stutaeng]

This guy is running a 8.6 10 bolt (same as the GMT400 8.5, I think) on a boosted 8.1:

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Look at his other videos, he's got some dyno numbers, but can't remember what they are...

BTW, 600 HP at the wheels on "low boost" (by itself) sounds a little too optimistic, but I don't really know much about boost to begin with...unless your interpretation of "low boost" is like 20 psi+, LOL. I'm sure you are doing other stuff as well to the engine.

 

[Anubis]

This guy is running a 8.6 10 bolt (same as the GMT400 8.5, I think) on a boosted 8.1:

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Look at his other videos, he's got some dyno numbers, but can't remember what they are...

BTW, 600 HP at the wheels on "low boost" (by itself) sounds a little too optimistic, but I don't really know much about boost to begin with...unless your interpretation of "low boost" is like 20 psi+, LOL. I'm sure you are doing other stuff as well to the engine.

Thanks for that link. I have seen those videos. The 8.1 is a turd compared to LS engines. 600 whp with a boosted LS 5.3 LS is actually easy to accomplish. 7-10 psi of boost should get it done. People make over 1000hp with these boosted junk yard 5.3’s no joke. I understand the skepticism if you havent experienced it first hand. Ever watch sloppy mechanics on YouTube? Check it out. My build is mild. My brothers….not so much.

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[stutaeng]

Yeah, pretty crazy stuff there! I'm not sure how the 10 bolt will last (long term) under that much power. That white truck has a 9.5".

Why don't you want to swap rear ends? Is your truck a 5 lug or 6 lug? The 6 lug is easier to upgrade. I think the 5 lug you have to get custom axles? Don't know. There's a AXN axle for sale on FBM locally right now for $150. The older ones used to go for $600, but since that's what the newer trucks are running they are starting to show up cheap now. AXN is pretty much a 14 bolt 9.5" in strength and between a 8.6" & 9.5" in weight, with large disc brake rotors.

 

[Anubis]

Yeah, pretty crazy stuff there! I'm not sure how the 10 bolt will last (long term) under that much power. That white truck has a 9.5".

Why don't you want to swap rear ends? Is your truck a 5 lug or 6 lug? The 6 lug is easier to upgrade. I think the 5 lug you have to get custom axles? Don't know. There's a AXN axle for sale on FBM locally right now for $150. The older ones used to go for $600, but since that's what the newer trucks are running they are starting to show up cheap now. AXN is pretty much a 14 bolt 9.5" in strength and between a 8.6" & 9.5" in weight, with large disc brake rotors.

I’m not opposed to swapping axles if needed. I have a G body 442 with the big rearend like the Grand National has (8.5” opposed to the standard 7.5”). In a car with 26” tires they will handle 700-800hp so that’s where my mind set is. Will the AXN bolt right into my 1990 and allow bolting up factory rims with the disk brake set up? I thought the rear to get was the 454 SS rearend? Mine is a 6 lug 4x4.

 

[stutaeng]

No, AXN won't be an easy swap...

454SS would be next to impossible to find at a reasonable price, and 5 lug. A 14 bolt 9.5" from a 2500 Light duty 4x4 would be a direct bolt-in swap for you though; it's basically the same axle as the 454SS with 6 lugs. I helped my brother swap a C2500 LD 3.73/G80 axle on his 90 RCSB C1500 3.08 open diff. (2wd vs 4x4 axle width is different in this generation.) Just needed new U bolts, conversion U joint, and brake fluid for the purge. Took us about 3 hours. Total cost was like $400 for everything, then he sold his 10 bolt for like $200, so a grand total of $200. Cheaper than a regear. Just a thought.

Edit: I don't know if that will work on 15" rims

 

[df2x4]

A 14 bolt 9.5" from a 2500 Light duty 4x4 would be a direct bolt-in swap for you though; it's basically the same axle as the 454SS with 6 lugs.

This, for sure. Your truck already being a six lug makes things so much easier.

A complete six lug 9.5" 14 bolt should be reasonably easy to find, check car-part.com

 

[Anubis]

Thanks guys. So for search criteria I think it would be safe to use a 1995 k2500 all of which were 6 lug correct?

 

[stutaeng]

No, only the 2500 "Light Duty" had 6 lugs. The "regular" 2500 were 8 lugs. Just look for a K2500 with 6 lug wheels. I don't know that on line search functions would actually have this option? Expand on the years though to get a better chance of finding one. I don't know when they started making those 2500LD trucks (maybe 88?), but I think they were at least made into 97. That's what ours came out of.

 

[Anubis]

Thanks for that clarification