The Rock40 Build (1 Viewer)

[SuperBuickGuy]

Yes, the wheelbase sits at exactly 102" now which I think is 12" longer than a stock FJ40.

The question about a 3 link came up before and the answer boils down to space. The FJ40 just doesn't have any (enough) to make it workable; at least on this particular truck. This problem was aggravated by the huge casting of the PRO Rock 60 also. I know lots of folks have done 3 link fronts but we were both shooting for a truck with a very low stance/low lift so it wouldn't work.

Here's how Ethan described it:

"Originally I had the front as a radius arm setup because there is NO room on the inside of the frame for a upper link bracket, the radius arm setup bound HORRIBLY so I had to scrap it, came up with the 4 link idea and made some paper mockup brackets and it STILL had a ton of bind.
The key is to get the axle NOT to rotate at all as it travels, if it rotates as it travels down both sides will move together just fine, but when you drop just one side the upper link measurement will change side to side. The frame end brackets mounting points have to be perfectly placed, and unless you are the luckiest person in the world it will never come out right by guessing.

You can draw it out on a large table or the ground by swinging a arc from a point as your lower link mount. You will need to know how long a lower link and how much of a bolt hole spread on the axle you will have. Vertical from the frame end lower hole measure up the same distance as your bolt hole spread, mark this spot and swing another arc. You now have the travel plane of the axle with no rotation.
Now mark two more points on your two axle-movement arcs, in the same "vertical" plane as the original two axle end holes (oh yeah, mark the two axle end bolt holes on the arcs as they would be at ride height or max up travel) if you follow down the arc lines and mark on the same vertical plane they should still be the same distance apart.

Now swing a arc from your upper mount hole mark the same radius as length you want your upper link (shorter links will move the frame end upper mount position forward of the lower link mount and closer together) For this project it has a 35" lower and a 32" upper. If you swing a arc from the upper axle end mount at both up travel points and lower travel points the point where the two arcs intersect will be the location for your upper frame end link mount.

Put the panhard wherever you like."

Does that clear it up any?
View attachment 957068
Here's a photo of the CAD drawn swing arcs.

thanks, it does... one other question, how did you survive on Pirate with less than a 107" WB?

 

[CreeperSleeper]

Yep, still love this 40. If you don't mind me asking, what is your axle width? Stock 80-series?

 

[Rock40]

thanks, it does... one other question, how did you survive on Pirate with less than a 107" WB?

LOL, I don't know If I had been really thinking ahead I probably would have stretched the frame/rear tub when I was doing all the body work on it. At the time, I still thought I might put a factory hardtop on it but after building the little "half cab", I'd never want a full top.

Yep, still love this 40. If you don't mind me asking, what is your axle width? Stock 80-series?

Yep, the rear is stock 80 series width. If I'm remembering right, that should be 63" WMS. The Pro Rock was narrowed to 63" WMS, I remember that for sure.

Although it's a bit goofy to have the GM front and the 80 rear, the 80 axle has done really well. I'm running all the stock shafts in it and haven't had any issues. Ground clearance is almost identical to the Dynatrac.

 

[CreeperSleeper]

That's what I thought. Tony and I were discussing your 40 a few weeks ago. I think I'm going to run 60 series axles with IFS hubs up front and spacers in the back (putting me at roughly 63" WMS). I may be bugging you for mounting locations and lengths of your links in a few years! LOL

 

[SuperBuickGuy]

I like your half-cab/dog kennel; unfortunately, with the people I hang out with - I need the jump seats. I know I'm not looking forward to making the 3 link work on the front of mine... however, my bigger fish to fry is finding a '60 (I realize yours is a dana 60) front end within a reasonable distance and reasonable price. I found one in Vancouver, but I'm just not into a 5 hour drive along with an hour of work in the rain....

 

[Rock40]

That's what I thought. Tony and I were discussing your 40 a few weeks ago. I think I'm going to run 60 series axles with IFS hubs up front and spacers in the back (putting me at roughly 63" WMS). I may be bugging you for mounting locations and lengths of your links in a few years! LOL

Cool man Why not go with the 80 rear though? You wouldn't have to run spacers, you get the benefit of FF+disc brakes and those axles can be found in the $400 or less range. After you cut off all the nonsense stock brackets, you're starting with a clean slate.

I'm happy to help with any link stuff. Ethan still has all the brackets saved as CAD files and tempting him with might save you some work.

 

[Rock40]

I like your half-cab/dog kennel; unfortunately, with the people I hang out with - I need the jump seats. I know I'm not looking forward to making the 3 link work on the front of mine... however, my bigger fish to fry is finding a '60 (I realize yours is a dana 60) front end within a reasonable distance and reasonable price. I found one in Vancouver, but I'm just not into a 5 hour drive along with an hour of work in the rain....

Yeah, that is the drawback to the half cab but it's been years since I even had the jumpseats installed in the truck. I'll probably do a write-up on the cab itself. If you like fiberglass work, it's not that bad I have it now so you can remove/install it within 5 minutes; total weight is only 30lbs or so compared to the ridiculously heavy factory top.

My buddy in Bellingham may have an FJ60 front; I'll ask him about it. He has many, many parts which have been disassembled and stored for years. What are you looking to spend?

 

[SuperBuickGuy]

My top is disassembled so storage isn't too bad (and I really doubt I'll ever put it back on until FJ40 #9 comes along).

Fiberglass I have a C3 Corvette that I did the body work on ... I can do it, but I hate it... which also informs why I haven't put the flares on it... but that's another discussion for another day.

Price, it depends what I get.... 4.88 gears and a locker - I'd expect to pay more than something that's full of water and ultimately just a housing.

 

[CreeperSleeper]

Cool man Why not go with the 80 rear though? You wouldn't have to run spacers, you get the benefit of FF+disc brakes and those axles can be found in the $400 or less range. After you cut off all the nonsense stock brackets, you're starting with a clean slate.

I'm happy to help with any link stuff. Ethan still has all the brackets saved as CAD files and tempting him with might save you some work.

The only reason I'm thinking of running 60 or 62 series axles front and rear is so I can buy a complete vehicle cheaply and part it out. If I end up with a great deal on just the axles, I may go that way instead just to save me time. I guess we will see what comes up!

 

[Rock40]

Price, it depends what I get.... 4.88 gears and a locker - I'd expect to pay more than something that's full of water and ultimately just a housing.

He has all stock stuff, entirely disassembled (3rds still together) and parts have been stored inside. You're going to take it all apart anyways....

 

[Rock40]

The only reason I'm thinking of running 60 or 62 series axles front and rear is so I can buy a complete vehicle cheaply and part it out. If I end up with a great deal on just the axles, I may go that way instead just to save me time. I guess we will see what comes up!

Yes, that makes sense. You could part an 80 too and do very well with that also. I took the front/rear axle from a 93' and my buddy parted the rest if the truck (no engine) he came away with over 3k and I sold the front high pinion for $650. Pretty good deal I thought. With the Hellfire knuckles, you could run 80 axles front/rear and they're definitely stronger then FJ60 stuff. Just food for thought.

 

[SuperBuickGuy]

He has all stock stuff, entirely disassembled (3rds still together) and parts have been stored inside. You're going to take it all apart anyways....

LOL, I always love the "while you're at it" way of doing things. I'd love to find an axle that someone has already spent the thousands on then decided they needed a dana axle.

 

[CreeperSleeper]

Yes, that makes sense. You could part an 80 too and do very well with that also. I took the front/rear axle from a 93' and my buddy parted the rest if the truck (no engine) he came away with over 3k and I sold the front high pinion for $650. Pretty good deal I thought. With the Hellfire knuckles, you could run 80 axles front/rear and they're definitely stronger then FJ60 stuff. Just food for thought.

Very true. And I can find 80 parts easier than 60/62 parts. However, after wheeling my 80 (very) hard, I have come to not like the front axle at all. I could possibly buy an 80 and 62 and part them both... *sigh* I think I need a bigger garage! LOL

 

[Rock40]

Huh, I very nearly used the 80 high pinion front in my build instead of going for the GM alternative. The Hellfire knuckles were coming out in about the next 6-12 months or so and the option was clearly cheaper than then Dynatrac; the damn Pro Rock housing cost over $2,200!! I also debated doing a Diamond housing using the high pinion 8" diff but I was worried about the 30 spline inner axles surviving long run.

Maybe I'm out of the loop (probably) but you're the first person I've heard who hasn't raved about the 80 front. I'm not doubting you in the least as I have no experience with it personally but I'm curious as to why. OEM knuckles and goofball steering aside, it's not that different from a standard Toyota axle like found in other Landcruisers or <86' mini trucks.

Please learn me something and reinforce why I didn't use that axle

 

[Rock40]

Crap, I though I had a photo of these side by side for comparison but I guess I don't

These are the OEM FJ80 30 spline shafts from a the 93' FJ80 and the bottom picture is the 35 spine domestic 4340 chromo stuff from Dutchman. No comparison but the Toyota stuff has held up fine so far.

Chad-Did you ever break your 80 rear while wheeling it?

 

[Rock40]

And mix in a set of these 300M joints back when was Bobby himself was still making them......

 

[CreeperSleeper]

On the rear, I broke 2 stock axle shafts and ended up twisting the splines so badly we couldn't pull the shaft out. This was a factory e-locker with 5.29's and I was running 37" Iroks.

On the front, I broke stock birfields (Longs held up), steering arm studs, hub studs, bent the housing (which is pretty common), and chewed the crap out of a 5.29 R&P. I was into that front axle at least once a year. Again, this was a full body 80 on 37's. Stock 1FZ, stock trans, stock case, mild lift, and as much "weight savings" as I could do.

 

[Rock40]

On the rear, I broke 2 stock axle shafts and ended up twisting the splines so badly we couldn't pull the shaft out. This was a factory e-locker with 5.29's and I was running 37" Iroks.

On the front, I broke stock birfields (Longs held up), steering arm studs, hub studs, bent the housing (which is pretty common), and chewed the crap out of a 5.29 R&P. I was into that front axle at least once a year. Again, this was a full body 80 on 37's. Stock 1FZ, stock trans, stock case, mild lift, and as much "weight savings" as I could do.

Good grief that's a lot of carnage on the front! With that history, I can understand your opinion. It makes you wonder if some of the axle wear/tear isn't contributed to the fact that the 5.29's are responsible for the gear reduction after upping to 37's. When the pinion gets smaller it's obviously going to loose some strength but does that transfer into more strain on the hub studs, steering studs, etc?

I'm surprised no one has freaked out about the 3.7 axle gears I run

 

[SuperBuickGuy]

meh.... it's like anything else - whatever works for you. 3.7 is low(ish) but it also depends on what's in your t-case because the ratio in the axles make little difference - it's the overall ratio that matters.

I've got 4.10s for my '40, but with the 1.96 low range of my transfer case, that will be problematic... however, it's not finished yet - so much can change. I'd like 4.88s... but I don't let perfect get in the way of done.

 

[Rock40]

And if you have a doubler, axle gears aren't nearly as important as long as you have enough HP to spin them. Low, low range is 202:1 with stock transfer case gears