Front Differential Swap??

hey guys, looking for a write up on a a full front diff replacement, a la ECGS type swap. I can order a full front diff from ECGS with 4.56s and swap it in, and would like a good write up or how to. The rear 3rd member looks easy, but don't know how involved the front is.

 

If you know how to change your CV's, you're halfway there. Drop the front driveshaft, unplug the connector on the actuator and the breather hose, then unbolt the two front mounts and the rear crossmember mount. The funky nut in the crossmember is a 12mm hex key IIRC.
Getting it out can be a bit of a pain, basically lay underneath it and bench press it up, then rotate it towards the front of the truck to get the stud out of the crossmember. Installation is the reverse.
The first time I did it it took me an hour to rotate it out correctly, by the 3rd time (it took ECGS 3 tries to send me the correct differential) I had it in and out in ten minutes.

 

Yikes, 3 times! How'd that happen?

Also thanks! I definitely know how to swap CVs so the rest sounds fairly easy.

 

Yeah, shouldn't be too hard, just have to monkey around with getting it out after everything is unbolted.
ECGS sent me the front diff for a 2012 the first time (mine's a 2002, I got the rear for the 2012 as well but they're the same), and the second time they sent me one with 4.88 gears (I have 4.56, although I kinda wish I had kept the 4.88). Third time was the charm though.

 

Ah I can see why they'd get mixed up the first time. Why did you wish you got 4.88s?

 

Didn't think I'd go up to 35's at the time, should have thought a little further down the road. Even with the SC it's a bit of a dog with 4.56 gears.

I recommend doublechecking your order with ECGS so you don't have to go through the same hassle.

 

@Blackdawg

What are they charging for the core?

 

I gotcha. Are you auto or 5 speed? What engine?

I'm on the fence about getting 4.88s. I wanna do a Toyota front axle swap one day, so I'll be keeping the rear axle the same so I have the same track width, and then go to 35s, but I'm not sure how long it'll be before that actually happens.

 

Should be $600 for a new diff, $900 with Core charge. Get 300 back when you send in a new diff. Thats with no locker or solid pinion collar or any options though.

Do yourself a favor and go 5.29s.

 

Do you know anything about that? I saw the option for CV bushing and solid spacer but not sure if either of those are necessary and the description doesn't really explain it.

I've got 3.4l and 5 speed so I think 5.29s would be overkill even for 35s. Especially on the highway. 4.88s might be okay with 33s for the time being before going to 35s. I don't plan to go bigger than that

 

The CV bushing isn't as crucial in our diffs as in 2nd gen diff, so up to you. Id definitely go for the solid pinion collar though. It sets the pinion bearing preload and a normal crush sleeve can loosen over time. Solid won't.

4.88s with the 33s and manual will be awesome. You'll love it. 5.29s and 35s with the manual are about the same in terms of low end torque/rpms. Almost identical really. If you add 35s to the 4.88s after driving with 33s, you'll probably wish you had 5.29s with the 35s.

So now you need to really REALLY figure out what you do with the truck and how often. Are 35s REALLY even worth it for you??? or are 33s going to be just fine.

Idk what you use your truck for mostly. And while you may say "eventually id like to ______" that should be ignored unless its going to happen within 6 months of the regear and always happen that way. Which is hard to predict anyways.

Im stressing this because regear is a HUGE decision. It cost a ton of money, it sucks to do even just swapping the thirds out is no picnic, and you only want to do it once. If your rig is a DD and occasionally sees some dirt miles. You have absolutely no reason to go to 35s other then the looks of it. Which honestly, is a terrible reason to put 35s on as it is a total bitch and puts a lot of stress on other components. A good 33'' tire is the way to go on these trucks. And if your truck is a DD first then maybe a toy. 4.56 is what id go for. If its more of a rig then a DD. 4.88s. If you're dead set on 35s and do almost nothing with the truck but offroad..5.29s all day.

You also should not be scared of high rpms on the highway. The 5vzfe will motor along all DAY at 3000rpms. You'll never have to down shift for a hill again. Ive driven mine thousands of miles on the highway like that. Totally happy too. It is well worth it for the offroad and in town performance. Sure i don't do 80mph anymore on the highway, i do 70...maybe 75 if im feeling it. But my mpg is better then it was with 4.10s and 33s at 70mph..

4.88s, 33s, manual tranny will be around 3000rpms for 70mph anyways.

i agree, 5.29s with 33s and manual will be major overkill and super undergeared.

But it is the best ratio for 35s by FAR. I don't think you'll find a single person that went 5.29s and wishes they had gone 4.88s that are running 35s. I can think of a couple dudes that did 4.88s though and wished they had gone 5.29s.



Sorry if this comes off as "preachy". Im not trying to be an asshole or judge your driving style or use of your truck..because i literally don't know how you use it, or how you want to use it.

I just want you to really really think about the choice to go to 35s hard before committing to it. Its an expensive mod no matter how you look at it and is harder on the truck over time. And you won't want to regear more than once..as that is expensive too. Not that you couldn't sell a pair of 4.88 diffs easily, but you won't get your money back on them fully.

Just something to consider and chew on while you think about it.

Again though. 33s and some skid plates will let these truck go a TON of places.


okay im done for now.

 

Thanks for the advice! If I do go to 35s at any point it will be after a SAS. So that's really pretty far down the road. Most folks I've talked to said that 4.56s are great for 33s and will basically bring it "back to stock". But if 4.88s would make a negligible difference then maybe I'll do that so that way I won't have to swap the rear again after doing that.

The truck is definitely 95% DD so I do have some concern with gas mileage. I want to find whatever is optimal for that first and foremost, for 33s. I already have a good set of bud built skids/bellypan so with the exception of a rear bumper I'm pretty well armored.

 

well there ya go!

So stick with 33s for now until the SAS happen, maybe by then you'll be ready for 37s

4.56s will be more torque than stock..but only just a little bit.

id go 4.88s personally. Think you'll enjoy them.

 

I wish we had a good line graph of MPGs and different gear ratios so I could start to see where the diminishing returns are lol

According to the grimmjeeper calculator I'd be about 100rpm over stock at 70 with 33s with 4.56/, and about 300 rpm over with 4.88s. If I put 35s on it'll be about 100rpm over stock with 4.88s. So I think I may just go with 4.88s since I'll bet my MPGs would be better just putzing around town on 33s and it'll be close to the stock feeling once I put 35s on (whenever that may be)

 

the grimmjeeper calc...is only half right. At least in my experience. allow me to explain.

So the calc told me that at XX mph id be doing XYZ rpms. cool.

I got the gear ratio and new big tires..took it for a drive..and wow look at that. The calc was dead on!

except it wasn't.

My speedo was reading XX at XYZrpms. BUT..my actual speed was almost 10mph low when checked with GPS. I think this is due to the fact the calc isn't correcting for the tire size..i know i know. It should and all that. But it isn't.

The calc says i should be a 2900ish rpms with 5.29s and 35s. But im actually at 3100-3200.

Just keep that in mind that the calc isn't 100% right

 

I have an auto with the 3.4.
Sounds like 4.88 is the right ratio for you. Solid choice for 33's, and will work for 35's eventually too.

Haha solid response man.

 

hmm, so err on the side of more RPMs than stated... damn. Gonna have to start adding some more algebra into this equation lol

 

I used the grimmjeeper calc as well to help decide. And after regear, new tires, and speedo correction using a Dakota Digital, my XX mph to XYZ RPMs are almost exactly what the calculator said it would be. My truck is a 3rz, not a 5vz, though. So perhaps there are errors in the calculator with certain engine/trans combos.

 

hmm, this seems contradictory to blackdawg's response. So is the calculator not accurate only if the speedo isn't correctly calibrated? Right now my speedo is 7.3% off, so I'm guessing I should add 7.3% to any gear ratio RPMs that I get when I do the calculation, given that I do NOT recalibrate my speedometer?

@Blackdawg, what's a 35" tire size if converted to xxx/xx/xx?

EDIT: Nvm I found a calculator that says 35x12.50x16 is 318/76/16, or 14.4% taller than the stock 265/70/16.

By adding 14.4% to 35s with 5.29s, the quoted RPM of 2986 RPM at 70mph goes up to 3415 RPM, does this sound correct?

nevermind, this math isn't right because the RPMs are the same regardless of tire size. I need to think about this later

 

Right now I'm getting 18.4 MPG, scrictly highway at 70 MPH, or 67ish on my speedo, according to my last calc (259.4 x 1.073) / 15.11 gal = 18.4.