Gadgedizzle

This is going to be something you might want to tackle if you want a night and day performance upgrade to your Toyota 2WD pickup! (Also relevant to 4wd which is very similar, but I'm exclusively covering the 2wd models in this discussion since it's the hardest one to upgrade.)

As some of you know already, I started a very undercover build of a 1992 2wd Reg cabToyota pickup.. I hastily chose to swap a 1996 Corvette Grand sport LT4 and T56 6-speed trans since it was there and I got it for a great price. As everyone knows, there's stuff you end up having to upgrade when you do this.. Brakes to slow it down, and an axle and suspension that will actually put that power to the ground!

So, today I talk about the axle..

Most Toyota 2wd 1/2 ton pickups come factory equipped with A-code 2-pinion 7.5" 27 spline open differentials. Earlier years of Toyota trucks DID however in fact come with a G-code 30-spline axle option, the one I found was a 1986 2wd 1/2 ton with 3.07 gears and a W46 4-speed Transmission. (G662, G-8", 66- 3.07:1, 2- 2-pinion diff.) Although they hold 350hp fairly well, it's an open differential. And with no Diff options available in the market, I decided to grab the stronger and more upgrade friendly Toyota 8".





The G662 axle is a good foundation but it's somewhat bitter sweet.. See, the G662 comes with super beefy 30 spline axles that are known to support over 800 turbo HP.. They're actually rumored to be stronger than stock Ford 9" axles. The bitter part is that although it does have the larger 8" ring gear, the housing is designed for a LARGE pinion 3.07 gear ratio which is not compatible with the more common gear sets available, and definitely not compatible with the Differential/gear set I decided to use.

So now that I know the 3rd is not what I need, I grabbed a 1994 4-runner 4x4 V6 axle and a MK3 Turbo Toyota supra LSD Differential.





The 4-runner has the beefy 4-pinion V6/Turbo 3rd member and will support almost any horsepower I want to make. however it's still an open differential which makes great 1-tire fires, but is bad for trying to put down the muscle.. First thing's first. Since I'm not using the 4-runner axle, I'm just gonna put the 3.07 3rd in it and get it out of my garage so I have room to work..



After that's out, I'm going to strip and paint the Axle housing.





While the paint is drying, I took the supra diff apart, and saved the 3.73 gear set and put it to the side. Took the V6 4-runner 3rd apart, and removed the 4-pinion diff and 4.55 Gear set. Now that the 3rd member is empty and cleaned, I can start upgrading the Supra LSD before install..

Here's how the clutches were installed in the LSD when I disassembled it.


For maximum performance, and most aggressive LSD lock up, you need to stagger clutch/steel/clutch/steel.. This is the way the clutch pack will be arranged when it gets re-installed.


This is the entire LSD, cleaned, and laid out on my bench ready to get measured, shimmed, upgraded, and put back together.. I purchased a WEIR Performance LSD upgrade for the supra diff.



After the upgrade, install the carrier using the stock supra bearings and using the truck outter bearing race on the right side.. All the backlash and preload is set perfect, gear mesh is also perfect. If you look, you see my dial indicator and Prusian blue on the gearset where I was checking mesh.. Everything worked out perfect. You'll notice that the adjuster is hanging off the right side just a little.. A couple threads maybe. This is ok. It's because the offset of the supra LSD ring gear flange is toward the left by about a 1/4 inch. Guys run this setup all the time and never have a problem, so I'm not at all worried about it..



After I installed the upgraded LSD, I used a brass cup plug to seal the hole in the 3rd member where the wheel speed sensor used to go.



Now that this is done, it's almost ready to go into the axle housing.. One thing left though.. Because the bearing adjuster is sticking out, it won't clear the axle housing. So you can take the adjuster to a machine shop and have them mill 0.200" off the face of it and re-install it, or you can remove about the same off of the ID of the flange in the axle housing.. I chose to modify the housing for this one.



So now as you can see, the 3rd fits like it was meant to be.



Now there's another problem.. The driver side axle fits perfect. But because the diff is pushed over to the right about a 1/4 inch, the 1/8" clearance that was there is gone, and the axle sticks out by about a 1/8" now. The only way to fix this? Shave a little more than 1/8" off the end of the axle.. So with surgical precision, I mauled off about a 1/8" or more with a very aggressive angle grinder wheel as to try not creating too much heat. Then cleaned it up a little with a 60-80 grit flap disc.. Pretty nice right?



Now that it's all together, It's time to put it in the truck.



There's a couple things about doing this brake swap that may throw you off a little.. YES you do need a shorter driveline. The 8" ring gear is not only larger, but the pinion is longer too.. The brake bias valve mounted to the axle needs to get deleted or you need to weld your old bracket to the axle housing since it doesn't exist. I decided for performance reasons to delete the rear brake proportioning valve. This gives me full control over brake bias and allows me to use a non biased line to run my hydro staging brake so I can initiate drifts when I'm sliding it at sonoma raceway and not have the line pressure cancelled by the bias valve..

When deleting the bias valve, DO NOT TEE THE LINES TOGETHER!! If you do this and your brake system leaks, you will lose ALL of your brakes since both front and rear circuits are connected. The CORRECT way is to block/cap the line coming from the front right brake line or remove the tee up front all together making the front line going to the rear bias valve dead. I didn't have a whole lot of time to remove lines etc, so I just traced lines up to the front, and blocked the line connected to the front circuit. I removed the rear hose bracket from the bias valve and bolted it directly to the frame using one of the old bolt holes from the old bias valve..

Look in this pic, I capped the line going to the front brake circuit, and zip tied it to the line connected to the rear brake circuit going to the master cylinder. no need to cut/flare tube. just unbolt the line from the bias valve and screw it into the rear brake hose going to the diff.



Here's the TEE I was talking about getting rid of up front.. This isn't my truck, just a pic I found online. It's the one on the right in this picture. Replace it with a union, or unbolt the line going to the rear and replace it with a 10mm x 1.0 inverted flare plug.




Now that the back brakes are going to be un-biased, they will lock up quite easily before the front brakes even think of locking up.. To overcome this, I purchased a Summit (Re-labeled Wilwood) proportioning valve. I think I paid like $20 for it.. Made a bracket and a line from spare 3/16 that I had laying around, and bolted it to the master cylinder up front.. Now I can dial in as much pressure as I need in the rear.



Of all the upgrades I've done, this was one of the most noticable, more so during low traction situations, wet roads, gravel, etc. No more one leg burnouts in the rain, and the brakes work better than ever..

I've also had people ask me about rear brakes.. Because the 8" and the 7.5" share the same backing plates, they share the same brakes and e-brake cables as well. So yes, you can re-use everything and retain your e-brake and regular drum brakes off your 7.5 so you don't have to spend money on brakes during the swap if you don't want to..

One thing I would do though.. I noticed the axle is about 1" narrower.. If you're still rocking the stock wheels, you won't even really notice it. I'm running 255/40R17's in the rear though, and this diff swap made me rub the inside of the bed on twisted driveways etc. I added longer studs to the axles and temporarily run a 1/4" wheel spacer until I can get my 3/4" billet ones and everything seems fine.

Good luck guys!

Gadgedizzle

I also forgot to mention.. To the guys rockin 8" with 6-lug axles.. You can also do this for your 4x4. Only difference is If you're V6/Turbo, you're only re-using your ring/pinion and simply using the MK3 supra LSD. If you're 4-cyl, you need the V6 3rd and re-use your ring/pinion and MK3 supra LSD. Both 4cyl and V6/turbo guys have to shave the passenger side axle more than 1/8" to fit correctly using the Supra LSD. No need to change brakes or any of that since none of it is affected since you're already set up with an 8" axle.

92 2wd

Very cool.

MudHippy

There are no 7.5" 4-pinion Toyota differentials. Unless you can show me one, proving there is.

And, whether you're aware of it or not, you failed to mention the write-up below.

Supra LSD into V6 truck 3rd

Gadgedizzle

I'm sorry, I was at work and severely distracted while I was writing this.. You are correct. The 7.5 DOES NOT have a 4-pinion diff. I was thinking the 8" for some reason.. The 8" Diffs are all 30 spline, 2 or 4-pinion for 4cyl, and 4-pinion for V6..

I haven't seen that web site you mentioned. Pretty cool though. And that's very close to what I did.. Except instead of running a crush sleeve on the pinion, I chose to run a factory Toyota "Drag" style collar/shim. Assemble the pinion, measure depth, and if all checks out, you install the sleeve, and keep pulling shim until you get the bearing preload within spec. Install your pinion seal, and I used a little Blue lock tite, torque it down and set the detent so it doesn't spin free.

BigBluePile

iTrader: (3)

Good job muddhippy.....

OP, very nice write up and upgrade! I hope I don't meet up along side your truck at a stop light I'll race you off road though

Tech Tim

Do you still have the Supra housing and stubs?

JohnnyCanuck

Very nice write up. Curious as to what you used to strip the paint off the rear-end housing, looks spotless.

Gadgedizzle

I used a 3M Paint/Rust stripper wheel.. If you've never used one, THEY'RE AMAZING..



And Thank you for calling out MudHippy.. I actually DIDN'T use that information when I went about making this rear end.. I've built a few Hybrid rear ends for different vehicles that I've owned.. Not exactly my first rodeo. Anyone that has a little common sense, creative thinking, the ability to look at, understand and parse data, and use a mic/caliper, has the ability to do stuff like this..

I mean after all, Where's the write up that shows you how to wire a LT4 Corvette engine into your 89-95 Toyota, and how to install etc? I'm being sarcastic.. if there is one, I didn't see it..

Stuwy123

iTrader: (1)

I installed an LSD in the rear diff of my truck.
It works great. I bumped up the spring rate by just adding a 1/8" thick washer behind the spring. Works great.
Although I wish I would've known about the WEIR kit. I would've been all over the extra holding power/grip on the LSD plates.

Oh well. I'll get it next time I'm in the rear diff.

Tech Tim

Do you still have the Supra housing and stubs?

sitnlow4life

Great write up
I was wondering if anyone has done this swap on a 7.5 axle with the 82-85 supra LSD ?
I have done some research and I know that the mk2 supra LSD is compatable with the 7.5 truck axle.
I'm just wondering if there are any issues I should be aware of .
Also every supra LSD I can find is 4.30 ratio
My truck is a 1992 2wd with a 3.58 ratio open diff right now.
I would like to keep the same ratio I have noe since I do a lot of highway driving and truck is cruising at 3000rpm at 65 mph

Thanks in advance

250000_yota

With those kind of rpms I don't think you've got the 3.58s. My new 2wd doesn't have a tach, but I do have 3.58s and I know for a fact mine isn't spinning at 3000@ 65. I'd double check your axle code. Mine has a F372.

sitnlow4life

Mine is also F372
It used to cruise at 65mph at around 2200rpm.
After I did I bunch of power upgrades from LCE it seems to cruise at around 3000rpm
The truck is a 5speed

250000_yota

See that doesn't make sense. What did you upgrade? Your cruising rpms shouldn't have changed with a manual transmission. Are you going off the sound of the motor or a tachometer?

sitnlow4life

Big bore throttle body
Efi pro camshaft
Headers
2.25 in exhaust no cat
Ported upper and lower intake manifold
Electric fan
No power steering or A/C
LCE wires
Egr delete

I I'm reading straight from the tach
The truck likes to cruise in the 2700-3000 rpm range

It will cruise down at 2100-2200 but it doesn't feel as smooth

250000_yota

So are you cruising in 4th or 5th? Cause now it's sounding like that's the main difference.

sitnlow4life

5th gear

osv

funny how you seldom see this mod on the rock crawler rigs... I think that it's just not as strong and/or doesn't lock as well, but the price is certainly right.

one of the really weak points on a Toyota truck rear end is the axles themselves, they bend pretty easily... i'm not sure that i'd want to grind 1/8" off of one of my new replacement axles, just to use this mod.

MudHippy

MASSIVE exaggeration^^^

I don't know how you managed to bend one(or if you really even did). But I can assure you it wasn't easy. And you didn't do it with an open diff, a stock transfer case, or tires smaller than 36's. And if you claim you did, it was a fluke. Good luck doing that again. And 1/8" off the end is inconsequential. Couldn't possibly make any difference.