FJ40 Upgrade: Offset Teraflex High Pinion D60, 14 Bolt Hybrid Rear Axle

[Rock40]

Should have posted this awhile ago, been picking away at it very slowly when time and the M715 project permit. I currently have an 80 series rear under my 40. Full float, disc brakes, ARB, RCV’s and set up to run TJ coils and links. It has never failed me BUT… I have well over 400 HP with the new LS and it’s only 30 spline.

First mistake: picked up a used Teraflex CRD60 on Marketplace. It was under a roughly 2600# buggy, how bad can it be?

So it was about a 60.5” WMS and it had cheap TG spacers on it. Ideally, I wanted about a 63” WMS. Fairly decent Wilwood brakes, guy said it had an ARB and 5:38’s. Started tearing it down.

I think these are Ford 9” bearing outers. Janky at best. RTV everywhere

 

[Rock40]

Had this goofy truss on it to support a single upper link

Pulled the diff cover OH MY

Airline has a patch and the locker case is absolutely hammered. I’m assuming a pinion broke and churned through the carrier at some point.

Shafts are junk

 

[Rock40]

Look at THIS shim stack! Determined that the carrier was for a 4:10 down ratio and the axle actually had 5:13’s not 5:38’s. So…. Someone had stacked this thick mess of shims over on the ring gear side to push the ring gear close enough to the pinion.

Carrier from the Teraflex on the left, new 4:56 (up) ARB on the right. See the ring gear mating surface difference? Oh. And it didn’t have an ARB as advertised. I believe it’s a Yukon Grizzly locker

At this point, there’s not much left to salvage that isn’t junk. In hindsight, I should have left the original tubes in and sleeved them. But I didn’t. Cut the tubes off and pressed the inners out. Tubes had a .010” tolerance fit

Sandblasted the housing and put it away. It was nearly the only thing of value on this purchase

 

[Rock40]

The housing sat on the shelf for a bit. Finally got new DOM tubes with a .375” wall. Had them machined for a .010” press fit as before. Polished the housing and the tubes where they press together

You can visualize the passenger offset here. Running an Orion case

Ultimately decided on using 14B spindles from RuffStuff. I don’t prefer semi float and oddly enough the bearings in the Ford 9” outers that were on it were dimensionally smaller than an FJ40 semi float axle bearing. Lame

Going with the 14B spindles allows you to use the large factory bearings + LOTS of brake options. + shaft options and hub configurations.

Made a spacer up to support the housing while the tubes get pressed in

 

[Rock40]

Found a place locally with a 300 ton press tall enough to do the axle. And it didn’t go super great

Short side went in ok, the long side must have galled up. And this was with heating the housing and freezing the tubes in liquid nitrogen. Anyway, they put nearly 250,000#s of pressure on it to make it seat . At one point, I was told it slipped in the press while under pressure which tore a nice chunk out of the housing near the tube. Was probably terrifying. I’d love to see how GM presses their stuff together at .030”-.035” press fit.

Single pass TIG on the spindle…

Double pass. Not coming out

DA’d the tubes and blasted the housing again. Yesterday, I MiG welded the plug welds and then TIG welded the tubes to the housing with NI99. 300 degree preheat and wrapped it up tight in a cheap Hobo Freight fiberglass blanket. Now we’re caught up

 

[Malleus]

More heat. You need to be at 500°F to soften the differential housing enough to achieve a 0.030" press. You have to be very careful, though. Any hotter than 625°F and you're into the annealing range. And they press both ends simultaneously.

 

[cruisermatt]

that's going to be a nice axle but what are you adding in terms on unsprung weight? funny you are thinking your fj80 rear is on borrowed time, I have never broken a stock fj80 shaft, with same HP, gearing, and probably 2500lbs more weight on it. Been on the same pair of shafts since 2016ish

 

[matzell]

that's going to be a nice axle but what are you adding in terms on unsprung weight? funny you are thinking your fj80 rear is on borrowed time, I have never broken a stock fj80 shaft, with same HP, gearing, and probably 2500lbs more weight on it. Been on the same pair of shafts since 2016ish

You are not wheeling hard enough! lol!

 

[cruisermatt]

You are not wheeling hard enough! lol!

I’ve managed to break just about everything else

 

[Rock40]

More heat. You need to be at 500°F to soften the differential housing enough to achieve a 0.030" press. You have to be very careful, though. Any hotter than 625°F and you're into the annealing range. And they press both ends simultaneously.

Interesting. I don’t know how hot they got it, I doubt 500, wasn’t there tho

 

[Malleus]

It's unlikely they would have had the heat, or used it if they had. That much tends to scare most people.

I spent a lot of time in the heat treat shop when I was an apprentice machinist. I tend to think less of hot stuff than I probably should.

 

[Rock40]

that's going to be a nice axle but what are you adding in terms on unsprung weight? funny you are thinking your fj80 rear is on borrowed time, I have never broken a stock fj80 shaft, with same HP, gearing, and probably 2500lbs more weight on it. Been on the same pair of shafts since 2016ish

Yeah, the 80 axle has held up WAY better than I ever would have expected. And it’s certainly mismatched to the Dynatrac 60 in the front. I’ve been debating an axle swap for years, mostly because I wanted to get away from the 30 spline shafts and the 1310 series Tom Woods shaft. After grenading 3 of them, their lifetime warranty no longer applies to me.

 

[Rock40]

It's unlikely they would have had the heat, or used it if they had. That much tends to scare most people.

I spent a lot of time in the heat treat shop when I was an apprentice machinist. I tend to think less of hot stuff than I probably should.

Very interesting, the effects of heat/cold is pretty wild. And I’ll say it again, sleeving the original tubes would have been WAY easier than a full re-tube

 

[Malleus]

The longevity is related to a lot more than just a single aspect of the axle: material, material treatment, size, method of assembly, etc. HAving been on the other side of the axle business, I can tell you that decisions are made that would piss you off, knowing it was going to cost you more than once...

 

[Rock40]

@cruisermatt , unsprung weight? Good question, I actually doubt that much tho overall. And I love the weight low down where it belongs

 

[peesalot]

we use a 25 thou interference on the press fit for tubes & inner C's.

 

[Rock40]

we use a 25 thou interference on the press fit for tubes & inner C's.

And that’s a LOT. If you've got a setup and know what you’re doing I imagine it’s probably not bad

Doing a one off axle and finding someone around here that would actually attempt it? Huge pain. Seems like the “Off Road” shops around here are doing 22” wheels and cheap lift kits. All of them told me to buzz off

 

[Rock40]

So I believe it welded up pretty decent with the preheat and the NI99 filler.

Blasted it again (4th time I think)

And shot it with Steel It. No more welding on it at this point

 

[peesalot]

I built a custom front using fj40 9.5 rear housing, filled & recut ring gear windows, used dand 60 from inner C's out, custom inners.
I was lucky enough to find a machine shop that had a lathe big enough to chuck the housing and turn the ends to true them on center and provide desired press fit with inner C's which we had in hand. I was able to heat them in the wifes oven to 425 ( IIRC) and pound/tap em on with a bfh so no press involved in my build. Did it in the garage on jack stands, got super lucky that it all came together, coulda siezed up and fubared my project, should have used a press but same as you, no have big press.

 

[Rock40]

I built a custom front using fj40 9.5 rear housing, filled & recut ring gear windows, used dand 60 from inner C's out, custom inners.
I was lucky enough to find a machine shop that had a lathe big enough to chuck the housing and turn the ends to true them on center and provide desired press fit with inner C's which we had in hand. I was able to heat them in the wifes oven to 425 ( IIRC) and pound/tap em on with a bfh so no press involved in my build. Did it in the garage on jack stands, got super lucky that it all came together, coulda siezed up and fubared my project, should have used a press but same as you, no have big press.

Wow, that sounds like a project for sure. I’m thinking that with the 0.010” press fit+welding the tubes+the truss I’ll fab for it that the chances of spinning a tube are likely slim. I’m guessing it’s much more likely that the Orion will come apart before that