Are there any low pinon 8" front diffs that will fit in an FJ80 front axle housing? (1 Viewer)

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DangerNoodle

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I'm not really sure if this is the right place to post this, but I'll ask anyway. I have a fully built FJ80 front axle on the 40 that I am building. I just got finished fabbing a 3-link for the front, but I'm thinking that I am going to have clearance issues with the high pinion of the 80 axle. I never thought that I would say that, but I managed to get the frame low enough, and the axle high enough, that it is a problem with the caster correctly set. Are there any 8" low pinion diffs that would fit into the 80 housing and work?
 
Here are a few pics. The panhard is not set yet, but I know that a slightly lower diff will help me clear the bellhousing and oil pan.

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The mini truck guys love the hp 80 fronts to replace the standard front diff. I would think a standard mini-truck front diff would fit.
 
The mini truck guys love the hp 80 fronts to replace the standard front diff. I would think a standard mini-truck front diff would fit.

Awesome! That's great to know.
 
If your diff is that high, why not run a traditional driveshaft instead of a DC driveshaft?
 
If your diff is that high, why not run a traditional driveshaft instead of a DC driveshaft?

Im thinking that I am going to run a traditional, but at full droop on drivers and full stuff on passenger, i start to hit my bellhousing and oil pan. A lower diff would let that clear by increasing the driveline angle.
 
the only issue with the low pinion diff in the 80 housing is the 80 tie rod that sits behind the axle, but I'm guessing you're doing a y-link/crossover and wont have this issue?
 
the only issue with the low pinion diff in the 80 housing is the 80 tie rod that sits behind the axle, but I'm guessing you're doing a y-link/crossover and wont have this issue?

I'll be running hellfire knuckles for the high steer and increased strength.
 
keep the HP and set bumps accordingly, that little extra stuff aint s*** and having that driveline a few inches higher is HUGE when you start bouldering with it.

agreed I smash my low pinion flanges on everything
 
keep the HP and set bumps accordingly, that little extra stuff aint s*** and having that driveline a few inches higher is HUGE when you start bouldering with it.

It would be maybe 4" of up travel at most with that HP. I could probably get more like 6" with the low pinion. I'm planning on trying to see what is possible once I get my steering and Panhard done, but I would like at least 4" of up travel in the end.
 
4" of up on a crawler is fine, mines at 4.25 and it rarely sees the bumps, leaf springs still and thats mainly on really twisted stuff or off camber. Unless you plan on some higher speed stuff over bumpy stuff. I personally would choose the highest, lowest angle set up for drivelines. I have a Dana 60 in the rear of my 40 now and was checking the difference in pinion hiegth on a 14 bolt in a 40 and it is significant, it gets fun when you are driving in a manner that your main concern is drivelines, enjoy.
 
Awesome project!!!

all the low pinion mini 8" diffs will fit in lieu of HP.

up travel is your best friend at speed, not super important crawling if your pulling 4" that's OK. whoops are a different story, and 7-8" would be a considerable advantage.

Lets see and hear more about this link setup. I just acquired a 68 FJ and have the fj80 Fr/Rr axle plan for it. My plan is to run full hydro steering with the Hellfire knuckles. 3 or 4 link front would be my objective.
 
Awesome project!!!

all the low pinion mini 8" diffs will fit in lieu of HP.

up travel is your best friend at speed, not super important crawling if your pulling 4" that's OK. whoops are a different story, and 7-8" would be a considerable advantage.

Lets see and hear more about this link setup. I just acquired a 68 FJ and have the fj80 Fr/Rr axle plan for it. My plan is to run full hydro steering with the Hellfire knuckles. 3 or 4 link front would be my objective.

Here is the build thread. It floats around in the 40 section.



If you have any questions about the link setup, let me know. I'd be glad to help.
 
Frame heigth on a soa 40 ?

1970 fj40, soa, shackle reversal, upper bushing of front shackle is thru frame, stock hangers other wise, reused the oem fixed end hanger in the front, on bias ply 38's, I got 25 to bottom of frame horn, 23- to bottom of frame rail at tcase
 
Frame heigth on a soa 40 ?

1970 fj40, soa, shackle reversal, upper bushing of front shackle is thru frame, stock hangers other wise, reused the oem fixed end hanger in the front, on bias ply 38's, I got 25 to bottom of frame horn, 23- to bottom of frame rail at tcase

Im at about 23 1/4" without any body panels except the tub, and with a full cage. Im soa on stock springs with a 4" shackle.
 
Yup, thats same, 4" shackle, FWIW I run stock front shock tower with 11.5 bilsteins, front bump contact surface is 3" doen from bottom of frame rail and the stop axle side is a 1.5" C channel welded down middle of spring plate( leaves just enough room to get deep socket on u-bolt nuts) I get roughly 3.5" up on the stop and 3.75 + on the shock. I have custom alcan springs that are a bit longer than stock springs for shackle angle and I moved the center pins out 1.5" to pick up some wb. They work well. after years like this I might go to a flatter spring and lower the whole deal like 3+". Would require rework of high steer/drag link but the overall hiegth reduction would be nice on the same tires, would require some fender work
 
You can also install an 8" TRD e-locker differential in the front. I think they come in at least two different ratios from the factory. I installed front and rear with 4.56 in an '85 4Runner years ago.
 

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