Swapping Tacoma rear end for an FJ80

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Winch

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Hey guys. I did a solid axle swap on my '02 Tacoma using an FJ80 front axle 4-5 years ago and it has been holding up great. During this time, I've now broken my 8" rear Tacoma TRD diff for the 3rd time. I really did not think it would break again because it was cryo'ed, professionally setup and I added a trackbar. I obviously cannot keep replacing these and decided on an FZJ80
diff (for one thing, it would match the front). Been doing a lot of searching and found answers for most of my questions, but still have a few, so would really appreciate any input. This is my DD, so the rear upgrade has to work both on the Hwy and off-road.
1. The FJ80 rear diff is off-centre, so my options are to:
a) have it re-tubed to get the diff centered. Sounds like an easy solution.
b) swap my centered T-case for an FJ80 off-centre T-case. I'm currently running dual gear driven T-cases. Does anyone know if there is an adaptor to add a crawlbox in front of an off-centered FJ case?
c) get a Diamond axle housing for the FJ80 diff, etc. Sounds like the most expensive option.
d) just run the off-centered diff with a double carden U-joint on both ends of the driveshaft. Would this work without any vibrations on the highway? Anyone doing this? Any pro's and con's to the above options. Any suggestions or input? Any options I haven't thought of (apart from other types of axles)

2. I've just invested $2000 + into my 15" rims, beadlocks and tires, so would not like to part with them yet. When, I did the SAS I swapped the rotors and calipers from a '91 FJ onto the '95 axle to fit the 15"rims. I would like to go with an FF setup w/ disk brakes but keep my 15" rims. Can this be done? The rims I have are the AR767 style steelies with the 3.5" backspacing IIRC. Are there parts, say mixing and matching from other vehichles that can make this happen? Or would I be stuck with drums and a semi-floater until such time that I go with 16 inchers and do a conversion?

OK, I think that is it for now, and I apologize for asking because I'm sure this have been covered before, I just couldn't find it. Gary.
 
Why dont you just buy a Ford 9". They are dime a dozen and really cheap to build.
 
There is not enough offset (3.69") in a 80 series rear axle that I would be stressed about it enough to go down the retube or custom housing path. 80 series rear - Pirate4x4.Com Bulletin Board

Given your location I am sure that you would not have too many problems swapping out the brake setup of of a post 8/92 production axle for a pre 8/92 production JDM rear disc setup that came from the factory with 15" wheels or even buying a complete FF pre 8/92 production JDM rear axle from the start.
 
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jasonmt said:
The rear discs are generally not a problem with 15" wheels, it is the larger front discs on post 8/92 production vehicles that cause the issues with 15" wheels.
Click to expand...

I've always heard it was the rear discs that won't accept 15" wheels.
 
I ran an 80 series rear in my lwb 84 pickup trail rig for a while. It'd only run up to about 40mph but I never noticed driveline vibes...but then again maybe the vibes were being assimilated with all the other rattles and groans :frown:.
 
15" wheels with 2" offset should clear the calipers.
 
the diamond housing shouldn't be that much, and to make it fit would be easy(obvious)

When we did a custom 3 link front and rear on a 4th gen 4 runner we used diamond housings.

On the rear housing we had diamond match the width of the original. It came with the flanges to bolt the original axle/bearing assemblies into the housing. The axle housing was also setup for the big landcruiser(Aprox. 9") differential. The splines on the original axles fit perfectly into the bigger diff.

It doesn't solve the full floater/rear disc prob.

It would seem like the easiest solution.
 
Thanks for the replies guys. So to confirm, the JDM axles prior to Aug 92, were FF with disk brakes and came with 15" wheels?

Yes, I'm really concerned about vibrations since my truck regularly sees 75 mph. The 3.69" offset is not that bad. I suppose it will be trial and error to see if two double carden CV joints would handle that or not. I still have not completely priced out a complete Diamond axle, but it would probably be around 2G's minimum.

Having the diff offset to the pass side would allow me to modify my budbuilt style trackbar and run that from the centre of the axle forwards. If I go with a Diamond or a centered FJ axle with E-locker, I don't think I would be able to fit the trackbar and will have to come up with a totally new design.
 
I have heard of some FJC's breaking the stock parts in the rear housings when taken off road extensively.

Also just FYI, with a DC rear shaft, I still get minor vibes that come and go at 40, 60, and 70mph. That is with my pinion pointed at the TC with 0 degrees U-joint angle at the pinion and a 12 degree driveline angle relative to the ground.
 
Re-tubing the 80 series diff or a Diamond housing sounds like the best route, IMO, if you want to keep it Toyota. If your not looking for the E-locker then don't limit yourself to the 80 series, use a 60 diff if you find one cheaper.

Either option will allow for what ever track width you want and you can use the brakes of your choice to work with existing wheels.
 
Re-tubing an 80 axle would not be easy since the tubes are not pressed in (obviously) and are more square-shaped and formed. You would then have to find a long-side axle and have it cut and resplined. Some folks on the boards have had an e-locked 80 axle twist at the splines, so not the best choice IMO. Beefed 4340 axles run $400-475.
 
Winch said:
Thanks for the replies guys. So to confirm, the JDM axles prior to Aug 92, were FF with disk brakes and came with 15" wheels?

Yes, I'm really concerned about vibrations since my truck regularly sees 75 mph. The 3.69" offset is not that bad. I suppose it will be trial and error to see if two double carden CV joints would handle that or not. I still have not completely priced out a complete Diamond axle, but it would probably be around 2G's minimum.

Having the diff offset to the pass side would allow me to modify my budbuilt style trackbar and run that from the centre of the axle forwards. If I go with a Diamond or a centered FJ axle with E-locker, I don't think I would be able to fit the trackbar and will have to come up with a totally new design.
Click to expand...

The JDM specific pre 8/92 rear rotors are 312x18 whilst the post 8/92 JDM and USM rear rotors are 336x18. Same calipers and pads are used but there is a difference in caliper brackets and brake tins.

As fr as the offset rear; if you have a leaf sprung rear trying the axle "as is" is not a real big investment in a set of spring perches and then you can go down the road of new housing, two piece shaft etc. if vibrations are an issue. Your truck is a crew cab with dual cases if I remember correctly so the rear drive line should still be reasonably long which will minimize the angles.
 
As long at the offset angle is less that the maximum operating angle of the u joint, there will be no vibration issues. The U joint doesn't care whether the angle is offset; it only cares what the total angle is. In fact, the u joint has no way of knowing whether the angle is offset in the horizontal plane or vertical plane.
 
*EDIT* this is a 2 year old thread. i hope he's figured it out by now.
 
Yeah, thanks guys. I ended up centering the diff by re-tubing the housing. I took DOM tubing with the same OD as the axle housing's ID, cut both sides and have the inserted tubing overlap the axle tubing by at least 3" on each side so I could weld it on straight. Haven't had any issues with it yet.
 
Curious, did you have new axle shafts made? Also, did you use an early axle to fit the 15" wheels? FF or SF?
 
wow that was a lot of work...

the 80 rear axle will swap into a tacoma with little vibration due to the offset of the pumpkin. there are a few guys on pirate running them with no issues.

BoogerWeldz also runs 15" wheels on an full floater rear with just clearancing the calipers, i believe.
 
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