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Ford 9" or Toyota 9.5" ff rear

11K views 28 replies 15 participants last post by  jcturbotoy 
#1 ·
I am trying to get parts together for a fj45 tubed buggy I am gonna build and am having trouble deciding what axle to run out back. Buggy is gonna be light so I don't want a heavy cast axle out back. Its gonna have a fj80 up front and run 37" tires. Probally be run a 3.8/700r4/doubler. If I do an 9inch it will be a semi-float with a nod spooled chunk, 31 spline axles in a stock housing. The FF toyota will be stock with a lunchbox. What would you guys run? Sorry in advance for my ignorance.
 
#5 · (Edited)
I would be looking to upgrade shafts anyway so I could do 6 lug 9" shafts. I wonder more about strength between the two diff's? Would the loss in diff strength of the 9.5 over the 9 be worth it for the full float axles? Also what do you guys think about toyota cases living behind a 300hp max SC 3.8? I already have this Marlin Dual case setup should I dump it and go to a box 4 rocks and a dana 300? or maybe a toybox/splitcase setup with the LC rear diff? I have a sf fj80 rear and a 70s ford 9inch sitting here so I would have the go looking for parts either way, either new 3rd and axles for the 9" or the whole housing for the Toy. I already have a 2003 4.3 but I am thinking I want to run a 3.8 instead just for upgradabilty? Isn't that what you run Doug?
 
#6 ·
I'd run the 9" because it's stronger. If it's not strong enough down the road, there is tons of support/ upgrades. You would be changing out the axle if this was the case with the toy axle.

My opinion on toy cases is that they are great for 4cyl mini trucks running 37's.
 
#9 · (Edited)
The 9" has much more upgrade potential... And potential to become a money pit.


If you got the $ to bling out a 9", do it.

Otherwise I'd run the basically stock FF 9.5" Toyota. Welded rather than a lunch box (stronger). 7/16" fine thread bolts rather than the stock studs in the axle ends.

I know of 2 guys running the described above axle, 1 with 4.3 v6 and 39" Reds and 1 with 3.4 v6 and 42 TSLs, both have had really good luck out them.

You'd basically have an axle with minimal $ worth of mods that should hold up decent.

if you start breakin the shit out of it, I really doubt the FJ80 front with 8" diff will hold up.

By then, you'll be ready for tons anyway.
 
#10 ·
Another rear option is a Diamond housing, 10 bolt spool (with a touch of machine work) and a set of 35 spline semi-float toy-Dana hybrid axle shafts. Stays 6 lug and uses Toyota bearings. You would also be able to use any type of rear disc setup that the mini- truck guys are using now.

IMOP this is the way to go with a 9.5 fj80 third.
 
#11 ·
I disagree.

Even If I were to build a semi-float axle with 9.5" center section, I'd still use Ford 9" type axle ends, simply because the bearings/seals are cheaper (and basically the same design).

Rear disc brake setups are also essentially the same, with one significant exception, the spacing of the Ford 9" axle/bearing end allows you to easily use cheaper simple weld on caliper brackets.
 
#12 ·
The custom housing kinda shoots the rear axle out of the price range for the build for me at this time. I have heard stories of guys running the hp8 in comp buggys with 37inch sticky's full of water and not having too many problems, I think they are comparable in strength to a 9.5 rear or they wouldnt have put them in FJ80's.

I am thinking the toy cases need to go and am in the process of trying to sell them on here wish a could afford an atlas. I have been looking into the 3.8 and the 60* 700r4 and its looking like the 5.3 out of the Malibu's will bolt up to that tranny too and they are cheap. Sound like they need some cash in supporting mods to be able to run them though.

I am gonna just sit on the rear axle choice while I gather parts and maybe something will fall in my lap.
 
#18 ·
No kidding, especially in a big ol solid steel pig (FJ40 like yours, or exocage Truggy like my old one, and we were both running 39.5 Iroks).

Hell, I'm considering putting FJ80 axles in a Geo Tracker with 33s in hopes that I can go WOT all the time and not break...:homer:
 
#17 ·
Full bling Toy duals can quickly get you into or nearly into Atlas money... if I was spending Atlas money, I'd want an Atlas not a couple old 4 banger t-cases. I'm with TBIToy, run the matching FJ rear with a couple small mods, and if you're breaking that up, you're undoubtedly going to be breaking the front too and need to move up to a stronger axle at both ends. Light buggy on 37's you'll probably be just fine as long as you're not rock bouncin.
 
#19 ·
Hey, I've been running fj80 axles in my cut down swb land cruiser (here in Aus) I broke my first axle last year and it was a stock axle. (now have chromos from poly) and it was my fault it broke.
Theyre behind a Lexus 4.0 v8, c4 and atlas on 40" stickys.

Another transfer option which is ran here alot Is a land rover lt230. It's got a 3.3#:1 low range and they are bloody strong!
There is a few places here that do adapters from the t700 to the lt aswell.

Ashcroft in the uk sell rebuild kits and there are reduction gears available too. I bought a 2nd hand one for $300
 
#25 ·
I bought a removable top fj45 project that had a 4.3/th350/downey adapter/Marlin dual cases and a taco elocker rear already in it. I am trying to decide what I want to use out of it all. Gonna narrow the rear of the tub so it doesn't flare like they do and use the tub for some structure so I don't have to use so much tube and try to keep the thing light. That is why I don't want to go to cast axles even though I probally should. I figured I could run the fj80 front for awhile unitil I can buy a custom housing and build a hybrid 9"hp center with fj80 outers(should be pretty stout with 37"s).
 
#28 ·
The A440 & 442 are monsters, I had a 91 fj80 with the 440 and that sucker was bigger then the allison's in the duramax trucks. They use them in industrial applications. If I was going to build a v8 fj80 I would use the 442 for ease of transfercase and driveshaft installation and build motormounts.
 
#29 ·
If your trying to keep it light id say go for the tacoma 8.4 rear its stronger than the v6 rear and imo almost as strong as the lc9.5 with load bolt. The pinion is the same size but the lc is 27 spline and the 8.4 is 30 spline. The 9.5 ring gear is bigger but the 8.4 has the brace that connects the bearing caps. Ive been running one for 3 years with 42 iroks and supercharged 3.4 and have not broken athe rear.
 
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