Let's talk about rear gear ratio on these 1500's, mostly street driving, limited towing

[Tavi]

I just recently discovered my dually was upgraded to 4.56s at some point in its life.

On 30 inch tires, the RPMs are a. It high at 80 (3,000). But I don't think there was much of a hit in the mileage. It gets 10 mpg unloaded, loaded, city or highway. 454 TBI. But it has much more pep than any other 454 TBI I have driven.

 

[1989GMCSIERRA]

My truck came with 3:08 gears. I put 35s on it and it fell on its face. I went to 4:56 and Auburn locker.
After 150,000 miles I regeared it to 4:10 and worn 35s later new 33s. With a Auburn locker.

I have trucks that will easily outtow my GMC. So it's really a project. But I found 4:10 to be a perfect all around gear. 4;56s were ok with 33s. 4:10 gave me more useable RPMs than 4:56s

 

[Biggershaft96]

Lol I did it the hard way. I gutted the 10-bolt and rebuilt it. Fortunately it was just a rear wheel drive.

I'd love to get a K2500 with the big block. Gas mileage might suck but my commute to work is only 4.5 miles, so who cares, lol. K2500's are not easy to find in my area.

youd be surprised how much gas you still go through having that short of a drive. I live less than a mile from my work and can still burn through $15 a week. that's also with a small block lol

 

[John Wayne]

Well considering I'm pretty ignorant on stuff like this. If I were fixing to lift my truck and wanted a regear, would it be best to just take out my front chunk and take it somewhere then or when really is the easiest? Is it like the rear where it doesn't really matter?

 

[redfishsc]

Well considering I'm pretty ignorant on stuff like this. If I were fixing to lift my truck and wanted a regear, would it be best to just take out my front chunk and take it somewhere then or when really is the easiest? Is it like the rear where it doesn't really matter?

OK I'm really not sure what you're asking here but I have an idea. I know if you are swapping the rear gearing on the cheap, find a salvage yard with a truck that has a rear end with the ratio you want, make sure the wheels are the same bolt pattern (or at least be sure you can swap the axle shafts), and just swap the whole rear assembly.

You absolutely MUST regear the front end also or you'll destroy something the first time you put it in 4WD.

I'm assuming you could do the same salvage yard swap with the front differential.

I do not recommend that you attempt to gut the differentials and regear both of them yourself unless you are very handy with the wrench. Doing the rear alone is tricky enough for a first-timer. But if you're pretty experienced and have done other things like engine swaps or new head gaskets, you might be just fine.

 

[John Wayne]

OK I'm really not sure what you're asking here but I have an idea. I know if you are swapping the rear gearing on the cheap, find a salvage yard with a truck that has a rear end with the ratio you want, make sure the wheels are the same bolt pattern (or at least be sure you can swap the axle shafts), and just swap the whole rear assembly.

You absolutely MUST regear the front end also or you'll destroy something the first time you put it in 4WD.

I'm assuming you could do the same salvage yard swap with the front differential.

I do not recommend that you attempt to gut the differentials and regear both of them yourself unless you are very handy with the wrench. Doing the rear alone is tricky enough for a first-timer. But if you're pretty experienced and have done other things like engine swaps or new head gaskets, you might be just fine.

I'm handy, I just don't trust myself enough to do it. I just didn't know if you have to have the front diff out for a regear and if so then it'd prob be easiest to do it then. That's what I was asking really. I'm going 33s and 22x12s and can't decide between 4.10s and 4.56s. afaik 4.56 never came in gmt400s tho or I'd go the route you suggested with a junkyard dive.

 

[1989GMCSIERRA]

You really need a few special tools to regear. If you don't set up the gear pinion depth and lash correctly you'll destroy the gears quickly.

For the front axle since it's IFS it's easier to pull the diff out but it can be done on the truck.
The rear axle is relatively easy. The 1/2ton C clip requires crushing a washer. It's a pita to do it unless you have the truck on a lift.

DONT swap the bearing caps or lose track of the shims you pul out left or right side. Keep them separate.
If I remember tight the 3/4-1 ton rears set up a bit different

It's been a while since I set up a c clip axle

 

[Jetson105]

I'm handy, I just don't trust myself enough to do it. I just didn't know if you have to have the front diff out for a regear and if so then it'd prob be easiest to do it then. That's what I was asking really. I'm going 33s and 22x12s and can't decide between 4.10s and 4.56s. afaik 4.56 never came in gmt400s tho or I'd go the route you suggested with a junkyard dive.

Don't know how common they were, but my 97 sales brochure lists 4.56 options in the towing guide for C/K 3500s with 5.7 and 7.4 (not diesel)

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[largewon62]

Well considering I'm pretty ignorant on stuff like this. If I were fixing to lift my truck and wanted a regear, would it be best to just take out my front chunk and take it somewhere then or when really is the easiest? Is it like the rear where it doesn't really matter?

I would definitely remove the front differential to regear it.

What do you plan to do with your truck.....four wheeling, heavy towing, light towing or do you live in a hilly or mountainous area? Those factor in on what gears you go with.

If you go with 285 that are 33" tall, 4.11 gears will give you the same rpms as factory 245 tires with 3.73 gears. If you want a little more umph and pulling power, some manufacturers make a 4.30 gear. That may be a better choice than 4.56 gears.
RPM @60 mph with 33" tire:

3.73 = 1595 rpm
4.11 = 1757 rpm
4.30 = 1838 rpm
4.56 = 1950 rpm

 

[Jeremy Dozier]

I am doing a rear gear change in my 14 bolt 9.5 diff from 3.42 to 3.73. My issue is the rear Pinion Bearing (Large) I cant find one for sale of the part # or dimensions. I can find the front bearing(small ) for days everywhere but not the Rear( Larger) help please !