Chevy/GMC differentials

[pmackiniv]

I'm trying to find either a 3.73 or 4.10 gear ratio rear differential out of a Chevy or gmc model out of a junk yard that would be compatible with a 1996 GMC Yukon SLT. Anyone know which models those might have come in?

 

[autolover3]

Curious why you are going for the junkyard axle route? What are you going to do for the front end?

And my 99 Yukon SLT has factory 3.73 open diff. I can't remember the RPO code but if you do a quick google search for OBS yukon RPO codes and find the codes for the 3.73 and than just check the vehicles you find at a junkyard

---------- Post added at 11:36 AM ---------- Previous post was at 11:31 AM ----------

I forgot I have alldata access on campus

This shows RPO code locations

This shows axle ratios

 

[pmackiniv]

I appreciate the help man. Let me first say that I know little to nothing when it comes to this sort of thing, but I would think that 4.56 gears would really kill what little mpg I already got going. As far as the front end goes, I was gonna wait till a little later on due to lack of funds. I have a lot I want to do and very lil money to do it. As far as the junk yard route goes, I figure it would be cheaper to find one out of there and maybe I could get a mechanic with the right machinery to put them in for me. I'm open to all suggestions. So whatever you think would be best I'm open to anything. Thanks man.


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[autolover3]

Well first I'm assuming your profile pic is your beast? Looks good IMO! I'm gonna guess 6 inch lift with 35's or so. Anything else done to it?

Going to a higher ratio will help get your speeds back into the powerband of your engine and help reduce stress on drivetrain trying to move heavy 35's. Depending on what ratio you have you "may" gain a slight improvement on mpg since you won't have to have foot into the pedal so much. Not saying a noticeable gain but you will also have useable power. Also regearing will put your rpm's higher while driving which reduces fuel economy.

And I feel your pain on lack of funds and a huge list of things you want to do, I myself am a college student and have a evergrowing mod list haha. You could do the rear diff as long as you DO NOT use 4wd until you get your front end done too. So take that into consideration. Also going the junkyard route is usually cheaper but also have in the back of your mind is that it is in a junkyard, something may have been wrong with the vehicle and it could be the rear diff among many other things. Also when getting a junkyard axle the bearings and gears could be worn badly which would mean rebuilding which takes money.

Not trying to scare you but always have to consider the worst case scenarios including funds, availability of daily driver etc etc.

All that being said find out what gear ratios you have and what other mods do you have? Hoping some other guys on here will have some input also!

 

[pmackiniv]

Oh yeah, that's the beast. I don't have whole lot done to it at all. Just the 6" lift on 35's. I got a cold air intake on it, but my buddy and I feel like that may be apart of the problem.


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[autolover3]

I wouldn't think the CAI would be causing any problems. On your other thread you asked if 4.56's will hurt fuel economy right?

Are you going for fuel economy or power? Having a lifted squarebody on heavy tires fuel economy just isn't going to be that great. Kind of a trade off we have to be willing to sacrifice to drive these vehicles. But there are things to help improve it though.

 

[pmackiniv]

What kind of things you got in mind? Ultimately I want to take stress off the engine and drivetrain, while at the same time seeing if there's anything I could do at all to increase MPG's. I would think 4.56 with a power programmer may get it back up to stock MPG's at 12 mpg.


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[autolover3]

I myself would go 4.10's for street/highway driving myself. I have 3.73s stock but with roughly 31-32" tires and am at about 2200 rpm on the interstate. Regearing for the extra tire height would help reduce stress on drivetrain.

And I among many would skip the programmer and get your PCM tuned, I have a Blackbear tune and love it. Also PCMforless and a few others if you search. Blackbear is a sponsor on here I believe.

Convert to electrical fans, your CAI, higher flowing exhaust (aftermarket headers, glasspacks or aftermarket muffler, high flow cats if wanted, DONT delete EGR) would being starting point. Of course these things will cost money and provide slight gains in economy but help with performance.

Here's what I have done so far: blackbear pcm tune, modified intake, removed intake baffle, throttle blade mod, pacesetter longtube headers, dual 2.5" into 3" single exit no cats or mufflers, Transgo HD2 shift kit, 32" mud tires, fresh differential gear oil (75w90 front, 80w90 rear if i recall.

It drives like a whole new machine, shift points are solid, good power, I was averaging 10-11 mpg a few weeks ago but it's been cold as hell in ND so considering idle time. If I didn't delete EGR I'd guestimate 15 avg I would have.

But now I'm in engines class and doing ZZ4 camshaft, beehive springs, roller tipped rockers (1.6 intake, 1.5 exhaust,) 1.6" exhaust valves, injector spider upgrade, ported throttle body, heads milled .010"

Hopefully gonna be a woop ass Yukon

---------- Post added at 06:08 PM ---------- Previous post was at 06:07 PM ----------

Also check this out!

http://www.tahoeyukonforum.com/forum/showthread.php?t=23591