New to me '97 K2500 'Burb with 2005 rear disc brakes/axle swap, Can you please help me identify what I bought?

GoToGuy said:

Who in there right mind would stuff an axle assembly w/ gear ratio that doesn't match?!?

Click to expand...

I talked to a GM mechanic who once test-drove a new truck that came from the factory by accident with different gears F/R

He took it out for a test drive on pavement and clicked it in 4x4 to confirm operation while moving, and when 4x4 engaged it about put him through the windshield.

I ran my Suburban for about a year with 3.73s in back and (OE) 3.42s in front, in 2x4-only of course.

I was trying-out the 3.73s to see if I liked them, as I might have gone to 4.10s or back to 3.42s. Since I don't drive the Sub that often it took me a lot of calendar time to make up my mind.

In the end, I kept the 3.73s in back and swapped a salvaged 3.73 assembly in front.

At least I finally fixed the disparity.

Evidently it's TBD whether OP's truck is different / same F&R.

If doing the test to see if the gearing is the same do it on grass or wet pavement

I do remember a local jeep four wheel drive shop has had a few problems . Once they installed a new diff assembly and sent it out. A few days and a weekend later the owner was back raising hell about his jeep. When it went into four wheel it would buck and fight itself. Lol. Turns out they didn't check the gear set, installed wrong ratio, " ahh, just grab any one ". Lol.

I have a GMT-800 14 bolt full floater rear axle with disc brakes prepared (new perches and bump stops welded to GMT 400 position) to go in a ‘94 K2500 6.5 w/ 4.10 gearing. While searching pik a part boneyards for the axle, it became clear they only came in 4.10 for the GMT 800 era.

I have a ‘99 K2500 6.5 that’s 3.73. I do have a spare 4.10 front differential. If I did the GMT 800 rear axle swap, I would swap the the front differential.

Big T said:

I have a GMT-800 14 bolt full floater rear axle with disc brakes prepared (new perches and bump stops welded to GMT 400 position) to go in a ‘94 K2500 6.5 w/ 4.10 gearing. While searching pik a part boneyards for the axle, it became clear they only came in 4.10 for the GMT 800 era.

I have a ‘99 K2500 6.5 that’s 3.73. I do have a spare 4.10 front differential. If I did the GMT 800 rear axle swap, I would swap the the front differential.

Click to expand...

I'm pretty sure all Duramax trucks had 3.73's.

I am doing the exact same thing as you are/did, and have the rearend from an 04 800 dually on my floor now to match up to my 99 400 dually. But I have to get it regeared to 4.10/4.11.

seems there are some great stories about 4x4 mixed matched gear ratios,. my 94 8600lb ecsb came with 3.42's, i lunched a tooth off the rear pinion pulling hard and heavy because a side bearing was worn,. i only had 3:73's to put in,. i drove that truck all one winter with 4x4 mixed match all the time,.. i didn't notice it ,.the only time i did feel it was dry pavement at 20-25 mph,. you could feel the front end twitch a little,. i don't run the 4x4 fast much

Keeper said:

I'm pretty sure all Duramax trucks had 3.73's.

Click to expand...

Those are the 11.5" axle, However.

Keeper said:

I am doing the exact same thing as you are/did, and have the rearend from an 04 800 dually on my floor now to match up to my 99 400 dually. But I have to get it regeared to 4.10/4.11.

Click to expand...

GM uses the 4.10 ratio.

phantom 309 said:

seems there are some great stories about 4x4 mixed matched gear ratios,. my 94 8600lb ecsb came with 3.42's, i lunched a tooth off the rear pinion pulling hard and heavy because a side bearing was worn,. i only had 3:73's to put in,. i drove that truck all one winter with 4x4 mixed match all the time,.. i didn't notice it ,.the only time i did feel it was dry pavement at 20-25 mph,. you could feel the front end twitch a little,. i don't run the 4x4 fast much

Click to expand...

That’s insane lol! I can imagine how happy the diffs and t case were

Sean Buick 76 said:

That’s insane lol! I can imagine how happy the diffs and t case were

Click to expand...

Yeah, that chain and sprocket assy in the T-case, literally caught between a hard place and a rock.

GotGoats said:

I am about to upload some pictures which will obviously make this identification much easier

Click to expand...

???