RPO CODES

[MrMarty51]

A guy over on Roundup is scrapping out a K2500 pickup.
I was wondering what the gear ratios is on that truck.
Had him snap a pic of the sticker.
I know nothing about them codes.
Can someone please tell me what gear ratios this truck has.

Thank You in advance.

 

[BIGR]

GT4 code is a 3:73 gear.

 

[BIGR]

 

[MrMarty51]

Next question, my truck at 70MPH is right about 2,000 to 2,100 RPM.
With the 3:73 gearing, whats other peoples tachs running at about 70 ?
Is it worth switching over to the taller 3:73 gears ?
Roundup is probably about 100 miles over from MC so I’d have that fuel plus whatever we can negotiate for price on his rear differential. I’d take the complete unit not just the gears.
Next think IDK if the rear out of his is a full floater.

 

[MrMarty51]

Yes, that truck does have the full floaters.
But does the K2500 pack as heavy of rear axle as the K3500 ?

 

[BIGR]

Next question, my truck at 70MPH is right about 2,000 to 2,100 RPM.
With the 3:73 gearing, whats other peoples tachs running at about 70 ?
Is it worth switching over to the taller 3:73 gears ?
Roundup is probably about 100 miles over from MC so I’d have that fuel plus whatever we can negotiate for price on his rear differential. I’d take the complete unit not just the gears.
Next think IDK if the rear out of his is a full floater.

My 2006 Chevy Duramax with the 6 speed Allison and 3:73 rear gears is turning 2000 RPM's at 77 mph if I recall correctly.

 

[dbrannon79]

iirc my 95 runs about 2200 give or take at 70 with 3:73's it has 265-75-16 all-terrain tires. but isn't yours a 4x4? you would need to swap both to 3:73 otherwise you wouldn't be able to use the front axle at all.

 

[dbrannon79]

you will loose towing capability with taller gears too. not a lot, but with a 6.5 you will notice the power loss pulling your dozer around! Especially trying to climb any grade. I didn't really save much on fuel mileage doing mine, but I am more comfortable keeping it at 70-75 not worrying about the rpm's as much for long trips.

Now with the 93 having 4:10's and the gear vendors unit, that is a night and day difference even between the 95 with larger tires and taller 3:73's the 93 has 245-75-16's and it runs just under 2000 at 70. my tach is slightly off, when I checked it with the TCC controller display, it was showing about 1900 doing 70. the funny thing is when it's locked in OD and 4th, when the TCC locks up the rpm will drop almost 400 rpm seeming like an extra gear! I know it's a huge expense over just swapping gears, but after experiencing the difference between the two, having "double OD' is well worth it. If you remember the old long nose cars like the olds and caddys back in the day what would float down the freeway, this 93 will float almost as good LOL this old truck has three things going for it.... it can tow (somewhat with the old worn out engine), it can cruise the freeway, and it can fog for mosquitoes all at the same time. HAHA!

 

[MrMarty51]

iirc my 95 runs about 2200 give or take at 70 with 3:73's it has 265-75-16 all-terrain tires. but isn't yours a 4x4? you would need to swap both to 3:73 otherwise you wouldn't be able to use the front axle at all.

Yes, it is a 4X4.
Your right.
I need to get this taller gear thing out of my head and get gear vendors in.

 

[DieselAmateur]

I really didn't like the 4.10 gears in my '95 and swapped everything out for 3.73. I was at close to 3k rpm doing 70 mph on the stock 265/75/16 tires

I don't think there's any significant difference in the rear end between a 2500 and 3500; the one difference could be the brake shoe width. Some SRW 3500 rear ends had 3.5" shoes where the standard issue on the 2500 was 2.5" shoes. I think the K2500 suburbans also had the 3.5" wide shoes. I doubt anyone would notice a difference in braking performance in the rear ends since the front brakes do most of the work. If really concerned about going from 3.5" shoes to 2.5" shoes you might be able to swap over the hubs to retain the larger shoes, or just do the GMT800 front brake upgrade, that's the most noticeable difference in braking performance for this platform

 

[ak diesel driver]

There also can be a bearing difference

 

[dbrannon79]

I would start looking online for a used gearvendors unit. look at their site and see which one you need, they are all the same unit other than the adapter and rear housing. the adapter replaces the tail housing on the trans or the transfer case, then the rear housing is what has the parts that connect the drive shaft yolk. they do sell parts and pieces, so if you run across a used one for a decent price and it's in good shape, all you'll need is the correct adapter and tail housing for your truck.

go with one that has the larger oil sump for added cooling too. on the controller, you will also need the vssb unit. they use the same VSSB that GM used on the 93-95 GM trucks. my 93 has two installed. one is for the gearvendors unit and the other is for the speedo in my truck. it uses it's own speed sensor and VSSB for the auto engagement. and make sure your wire in the 4x4 lockout on it so when you put the truck in 4x4 the gearvendor unit is locked out and won't engage. a new unit specked out for your truck will come with everything you need to install and wire it in.

 

[DieselAmateur]

@ak diesel driver bearing differences where, the axle tubes, pinion, hubs?

 

[dbrannon79]

If the 2500 has a full floater diff, it should be the same as our 3500's other than the brake shoe width. if's it's not a full floater, then it all will be different. it will fit, but bearings and all will be different size.

 

[Turbine Doc]

A guy over on Roundup is scrapping out a K2500 pickup.
I was wondering what the gear ratios is on that truck.
Had him snap a pic of the sticker.
I know nothing about them codes.
Can someone please tell me what gear ratios this truck has.
View attachment 99785
Thank You in advance.

G

Thread 'Probably the most complete RPO list I've seen yet'

May 2, 2012

All 187 pages of it;

View attachment RPO.pdf

Enjoy.

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• Forum: 6.2 and 6.5 Technical Reference Library