Front Axle 8.25", 9.25", K1, K2, K3

xXxPARAGONxXx · Jun 1, 2022

I was reviewing the "Front Drive Axle" section in the 2000 C/K service manual, volume 1, pages 4-54 – 4-102.

In this section, there is consistent distinction between the front axle on K1 and K2 models versus K3 models.

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However, my understanding was that the K2500 and K3500 both had the 9.25" front differential, while the K1500 had the 8.25" front differential. By K1, K2, and K3, I assume the service manual is referring to the K1500, K2500, and K3500, respectively. Correct?

Do the K2 (K2500) and K3 (K3500) share the same 9.25" front differential? Any idea why the service manual distinguishes the K2 from the K3?

DonYukon · Jun 1, 2022

I know the 2500 and 3500 share the same front end as in HS i helped a friend swap one over from a junkyard. I distinctly remember some small issues with taking it out and putting it in but next to each other they look the exact same

Schurkey · Jun 2, 2022

I noticed the same thing in my '97 service manual.

I have therefore "translated" the manual this way:

K1 and K2 = Six lug axles
K3 = 8 lug axles including 8-lug K2500s

If that's not correct for some applications in the manual, I don't know about 'em.

stutaeng · Jun 2, 2022

Yes, most likely the confusion about the 2500 Light Duty with 6 lugs having the same front differential as a regular 1500.

6 lug = 8.25" IFS differential
8 lug = 9.25" IFS differential

RichLo · Jun 2, 2022

^ What he said

xXxPARAGONxXx · Jun 2, 2022

Thank you. That makes sense.

Jesse_Wenting · Jun 2, 2022

stutaeng said:
Yes, most likely the confusion about the 2500 Light Duty with 6 lugs having the same front differential as a regular 1500.

6 lug = 8.25" IFS differential
8 lug = 9.25" IFS differential

Just for the quacks, 1500 trucks with the 6 lug 14 bolt rear end would've still gotten an 8.25" IFS in the front, correct?

There was never a 6 lug version of the 9.25" IFS diff, correct?

stutaeng · Jun 2, 2022

Jesse_Wenting said:
Just for the quacks, 1500 trucks with the 6 lug 14 bolt rear end would've still gotten an 8.25" IFS in the front, correct?

There was never a 6 lug version of the 9.25" IFS diff, correct?

Correct

Heavyhalf88 · Oct 30, 2023

I have a 1988 k2500 six lug. 14 bolt rear and big front. It’s the 9.5 with hubs that bolt right to my cv axles. 3:42 ratio with the 9.5 14 bolt rear. Has the small ujoints from a 1500. Big brakes. 12” clutch. All factory. It all works. I’ve had to repair the front end is why I know it’s not a half ton front. And bought 2500 u joints and were too big. 1500 u joints were same. It’s weird. Getrag 5 speed, 350, 241 t case. Ac red interior and dash. No factory tach 36 gallon fuel tank. So they are out there. Mines 100%original and rpo codes verify. So.

GoToGuy · Oct 30, 2023

There's probably a formula that GM engineering used to chart what combination of half shafts, u joints, center differential, drive shaft , two piece drive shaft, auto, manual, towing , buildup that fit their plan.
The thing I'm most impressed with is how many parts from from K/C 1500 thru K/C 3500 and a span of many years will interchange and bolt right up. That is some forward thinking! :waytogo:

Front Axle 8.25", 9.25", K1, K2, K3

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