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

[1998_K1500_Sub]

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

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.

 

[Sean Buick 76]

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

 

[GoToGuy]

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.

 

[Big T]

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.

 

[Keeper]

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.

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.

 

[phantom 309]

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

 

[454cid]

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

Those are the 11.5" axle, However.

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.

GM uses the 4.10 ratio.

 

[Sean Buick 76]

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

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

 

[1998_K1500_Sub]

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

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

 

[Schurkey]

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

???