IFS front Diff Questions
 

OK so I am probably going to get brow beat on this one.

I have a 95 4runner with IFS still, I have a 3.0. I also have a front IFS diff and all the associated junk from a 90 4cyl.

My plan is to have the 90 IFS diff rebuilt and re-geared to 4:88. I will also do the CV's at the same time.

My reasoning for this is multifold.
1. The 90 diff does not have the vacuum operated engager thingy. Some of my friends have had issues with the unit and rendered their 4wd inoperable at unfortunate times. This front diff will have less moving parts to fail. Yes it is an unlikely failure, but if it can be eliminated that is good

2. I won't be running a front locker; this truck is going to be purposely built for moderate/expedition type wheeling.

3. I can take my sweet time. I can get the diff rebuilt/regeared, then bring it home do the CV’s at my leisure. After the unit is finished, the only down time will be pulling the old diff and installing the new one. This is my DD, so I need to be able to finish the install in a weekend

My questions/concerns are as follows:

1. Is there a difference between a V-6 IFS diff and a 4cyl IFS diff. They are both 7.5” to my knowledge, but are any of the internals different?

2. The front frame truss from Sonoran steel, Downey and others come in two sizes, one being ½” larger than the other. Are the axle assembly’s also different sizes? Will it make a difference on install?


This truck will NOT be getting a SAS, I am looking at trail rigs, with the intention of keeping my current runner as unmolested as possible. The final build it will have a rear locker, 1.5” suspension and 33x10.5, and beefed steering.

1. No the 7.5" front IFS diff is the same for 4cyl and 6cyl. (aside from the ADD issue)

2. Can't help you on that one.


I can offer you a little advice when it comes time to change your diff:

1. Make sure you got lots of extensions, getting the cv nuts off seemed to be easiest from the wheel well.
2. An extra set of hands is great when it comes time to take out the diff.
3. when you have the diff out, pound out the studs for the cv's. It will make install a TON easier.
4. when installing the diff, bolt up the cv joints first, then rotate the diff into place.

Frames are different depending on tweakage and year and model.

Don't waste your money on anything but the Sonoran steel one.

Also, it doesn't matter with sonoran, becasue you measure your truck, and steve builds them to your specs.

Yeah, the sonoran steel one will be the route I go. I saw the prototype a few years back and was sold. The other ones look more like bling rather than functional.

i run the total choas one and it's been holding up fine, just measure

If you take out the ADD, you NEED to convert to manual hubs also, or you're asking for possible transfer case issues as the driveshaft will be spinning in the tcase all the time.

Why not lock it while you have it out? ESPECIALLY for expedition use, I would want all the capability I could get!

Swapping diffs shouldn't even take a full day, let alone a weekend.

tc.. I like to take my sweet time, i don't like doing anything quickly

I have manual hubs.. first mod.

My 89 p/u had no add.

The ADD t-case has the N position on the shifter, the non-ADD does not. So I am thinking, in tow the runner would be better off with the ADD case, Neutral setting and all. Just an option, in the event the truck needs to be towed. In my years, trucks have had to be flat towed now and then. (the dudes I run with that I call at 3AM don't have duallies and twin axle haulers)

I guess I will look at the setup a little closer, but I'm thinking the t-case setup should not be an issue. When you installed your duals, did you have an issue with the vacuum shifter? You went with 2 gear driven right? Both those did not come with v6/ADD from the factory. IRCC

Again, looking for all the tech stuff here

:drink: :drink: :drink: :drink: :drink: :drink: :drink: :drink:

When I say Expedition use, I "Should" lock the front, but I want this truck to remain as factory as possible. I can go back later and do the ARB, if needed. OK you talked me into the air locker for the front. I was going to do the compressor already.

For the type of Expos I like to do... In Northern Nevada.... Front locker would be nice, but not neccesary, i still like the idea... but I want to keep this truck out of the crazy $#!t as much as possible. I get into enough trouble with open diffs....

I kind of want to do what ya'all are doing and go with two trucks, one for rock pounding (for me..to be built later fj40) and one for high speed/expo/ all around.

I have been contemplatining LT for the runner down the road, so keep that in mind. The non ADD diff seems like a better idea to be compatible for Total Chaos. Less stuff to go wrong. I'll be getting the beefed up idler right after the lift.

My truck has 90K on it and I want another 100K before seriously cutting/welding etc.... Why? I don't really know, seems like 200K is a good number for that.

I just want to run the IFS in THIS truck for a little while. Hell, the special forces run IFS Toyota, before hummer, so it can't be all that bad right???

with lock out hubs only when they are locked would t-case turn, and of course you wouldn't want to make a habit out of running them that way.

As for towing in N you better research that, I've read that some t-case will oil starve if that's done without pulling rear drive shaft and front hubs unlocked. Better research that.

The biggest PIA with swapping out front diffs is breaking loose the CV axle studs. other than that easy swap. replace the studs, with high tensile bolts, will make later change out easier.

Good call on the locker. You'll be glad you did.

Btw, my non ADD tcase in my 95 has the N position too...

The diff is pretty easy to swap but it's a little heavier than you'd think. Make sure you have some help. As mentioned a long extension makes the CV nuts easier to remove. I used a 3' extension my Dad had that made the job cake. Also be sure to mark the driveshaft in case it comes apart so you can reindex it.

Don't buy into the SAS bull around here. Your IFS is plenty capable and won't need to be replaced until it is your limiting factor. I have no intentions of replacing mine unless I have a catastrophic failure.

The ADD is switched by the 4WD indicator light circuit - didn't have any issues when I put in the gear drive cases.

Once you lock up the front, the chances of breaking a front cv axle doubles. I don't think you'll have to worry too much if you're just trail riding. Just don't bind up the front wheels.

Actually thats about 90% false. The ONLY time that is true is in a "wedged" situation, where one wheel is pinned in a crack between two rocks. Open, that wheel wouldn't spin, the other would, but with a locker, the axle gets a lot of pressure.

With an ARB, that statement is completely false, as you can just turn it off in that one situation.

I've seen a LOT of CV breakage. 95% were on open front trucks, with one wheel in the air, spinning wildly, and then the truck bounces, the wheel comes down, and the axle snaps.

I've seen two front locker breaks, one was in a truck that had no rear, and was going too fast in double low, and the other was on a truck with TONS of gearing in the situation I described.

yes...your case has 45 mm OD journals whereas the V6 model has the larger 50mm journals. That means you need a master install kit that has the correct carrier bearings. Everything else is the same.

Thank you ZUK! That is the kind of stuff I was looking for. I understand you don't rebuild IFS thirds right?

After seeing Tims first rebuild, and your subsequent repair, I am a little nervous to take that diff anywhere.

Hey now, I resemble those remarks!

No, seriously - 200:1 crawl ratio, sending essentially 36,000 ft-lbs of torque to ONE wheel, it wan't a surprise when the shaft broke.

Oh ya...I rebuild the 86 thru 95 IFS fronts.....just not the Tacoma IFS fronts.