Mismatched diffs….

I picked up a 2004 double cab a couple weeks ago. The previous owner mentioned he had replaced the front differential at some point. On the test drive I checked the four-wheel-drive and it engaged fine but I didn’t have any gravel around to do a good test on it so I backed up till it unlocked and I took the thing home.

Fast-forward to a few days ago, I had the chance to test the four-wheel-drive a little more and it engaged fine but felt a little weird while driving and took a long time to disengage and when it did, there was a pretty good bang. A couple days ago it started snowing here and the thing could barely move through the snow.

Well it turns out the bang was my driver’s CV axle going. And after jacking the tires up and crawling around under the truck for a while, it looks like the front diff is a 3.90 and the rear diff is 4.10.

So what do you all think i should do? Find a 4.10 front diff and swap it out which looks like a bit of a pain. Or find a 3.90 rear diff which is maybe slightly less of a pain but also would give me the opportunity to throw a locker in there while I’m at it. Or run taller tires on the rear axle and forget about it?

Im getting about 11 mpg so says the first tank, so part of me is thinking maybe 3.90’s would help with that… also not too worried about rock crawling, this is just a camping/adventure rig for now.

I’m an old hand with Toyotas, but this is the first Tundra I’ve owned.

Cheers, Jerod

2004 Double Cab SR5 V8

 

Find a 4.10 front for sure. Your truck was made with 4.10's. That guy probably put the wrong front gearing in from the wrong truck configuration.
You need to either buy new front 4.10 ring and pinion, go to a junk yard and find another 04 double cab front diff, or any 01-07 Sequoia front diff, or a 00-04 manual v6 front diff.
All those had 4.10's.

2000-2003
3.91 - V8, 4x4, auto trans
3.92 - V8, 4x2, auto trans
4.08 - V6, 4x2, auto trans or manual trans
4.10 - V6, 4x4, manual trans
4.30 - V6, 4x4, auto trans

2004, Regular Cab or Access Cab
3.91 - V8, 4x4, auto trans
3.92 - V8, 4x2, auto trans
4.08 - V6, 4x2, auto trans or manual trans
4.10 - V6, 4x4, manual trans
4.30 - V6, 4x4, auto trans

2004, Double Cab
4.08 - V8, 4x2, auto trans
4.10 - V8, 4x4, auto trans

2005-2006
3.77 - V6, 4x2, auto trans
3.91 - V8, 4x4, auto trans
3.92 - V8, 4x2, auto trans
4.08 - V6, 4x2, manual trans

You could go with the 3.9X gearing if you wanted, it might be easier to find. But I'd stick with he 4.10's for sure.

 

You’ll probably get better MPGs with the 4.10s. Which is counterintuitive at first because the engine will be spinning at a higher RPM, but it will be much closer to peak torque and horsepower, requiring less throttle. The lower gear also aids in acceleration power.

 

Just the 04 4x4, although I don't know if 4.08 is close enough. I've heard you can get away with mixing the 3.91 and 3.92. I always wonder why Toyota even bothered to make the 3.91 and 4.08, when they couldn've simply had 3.92 and 4.10... hell even just 4.10 would have been simplest haha

 

Grab the front diff from a sequoia. They're all 4.10 iirc.

 

FGT folk knowledge blows me away. Like how most of you all know your stuff.

 

I love a nice consensus! I’ll start looking for a new front diff. I gather that Tundra, Sequoia, 4Runner, and Tacoma all share a front diff family, is any one better than another? Any problems with different ADD plugs or the like? Thanks in advance.

 

@des2mtn might be able to answer that better

 

Correct. The add motors might be different but thats easy to change. Lots of 1st gen tacoma came with 4.10s as well

 

Your profile doesn’t say what area you live in, but before you swap any diffs, check that rear pumpkin for rust. If the rear is crusted up, then replacing the rear axle may need to be done at some point anyway. I agree with all saying the truck would be better off with the 4.10s if not 4.30s.

 

4.30's would be sick.
If I ever come across any in a junk yard I'm snagging em

 

I'll let others more knowledge than I answer "better than another" but as for the connector, the Tundra 03 -06/Sequoia 02 - 04 use the same connector and would assume looking at circuitry that the internals of the ADD itself are same between those years.

While the connector itself is same for the 05 - 06 Sequoia. they took a different turn in design according to their circuitry.

 

I'll also note this. Tinkers' Adventures just posted a video with his 2nd gen RCSB. And he notes the CV's from LAPS have different joint system so there's that.

I'd highly recommend OE for the axels.
https://youtu.be/ihErEq6SRrk?si=SttplYW0G3n6QBkV

 

I’m in Oregon, but the truck looks like it was in Texas in a different life. Pretty clean underneath. I appreciate the help. I’ll let you know what I end up finding for it.

 

If the connector is an issue and you don't want to deal with re-pinning, you can also take the ADD tube/ actuator off the currently installed diff and put it onto a donor.

 

I ended up finding a diff out of a 3rd Gen 4Runner. Conveniently one I owned but was selling because it needed head gaskets anyway. So I lost a little on that sale by stealing the diff, but found the part I needed in my front yard…

I had to swap out the ADD control mechanism, but other than that the swap went smoothly.

I appreciate the help here!