Full Float Rear Axle Conversion - and FF mods

[GLTHFJ60]

This is his rig:

https://forum.ih8mud.com/vehicles-t...2-built-expedition-fj62-sale.html#post3832116

Getting back to the 60 FF conversion, I got mine because when I break an axleshaft on the trail somewhere, I want to be able to get the rig home. I don't want it to come apart and have a tire come right off the truck. That could cause some other damage.

Oh yeah and it's cool

 

[Tinker]

Spooky -
The mini-hub adapter you're talking about only works on a 40. I made a pair, had 'em powdercoated, & found out the holes don't match up to my 60 FF. So then I talked the guys at TSM into making a pair (I'd done all the measuring & drawing, & they already had 1/2 of it done with their SF brackets like you have).

So I have the prototype pair of TSM 60FF to 60 front caliper brackets sitting on the axle in my shop. I'm high-centered on making backing plates (some guys even take their front ones off, I know). But as soon as I finish a big job at work I'm back on 'em.

Found out that a prop valve only dampens the spike in line pressure when you hit the brakes & the pressure rises after that. Because of that I'm looking for a pair of calipers with pistons smaller than a 60 front. PMd CruiserDan & he said Toyota doesn't list calipers by mounting hole spacing or rotor thickness.

NT -
Any clue what year mini-truck calipers would have 90mm mounting bolt spacing & fit over a 20mm rotor? I have an '85 & an '89 so I guess I could check those if I wasn't too lazy to pull a couple of wheels.

 

[mrlocksmith]

Geez, you could get Poly axles for the cost of shipping alone, and still have commonly available parts availability wherever you go...why go with the FF?

Thanks all for posting, I'll check the Poly Axles out, Mark from Mark's Off Road Mentioned them to me too.


The reason for doing this is that my Expo Build loaded hit the scales at 6400 LBS !


I have talked to a few of the Guru's and they did not seem as overly concerned as I was about braking an Axle as long as I was not doing anything wild, which probably would not do in this rig anyway.

Thanks


Mark

 

[Spike Strip]

I bought the used FF from MAF - It came drum to drum. Used my 3rd but screwed up the pinion preload when replacing the pinion seal, so I decided, while I had it out, to go with an ARB Air Locker and 4.11's front and rear...

Brakes and drums and everything else was good so I reused all that stuff.

Rebuilding the axle with the kit is Almost the same as the front axle.

I think I spent around $600 (w/tax) for the axle and the rebuild kit.

 

[ntsqd]

I'd start by tracking down a set of those early fixed 2wd mini-truck front calipers. Say late 70's to early 80's somewhere. My '86 RET has floaters. The rear caliper's piston area can be significantly smaller and still work exceptionally well. After that I think we're looking at some of the passenger car stuff. Though most of that, AFAIK, is a floating design.

The reason that floating calipers have a less firm pedal is because of caliper body flex. When I worked at wilwood we designed & built a tool to measure caliper distortion under pressure. It was pretty amazing, some of the calipers you could watch distort as the pressure increased. Those that distorted the most were the floating types. This is due to the usual caliper body shape used for these calipers. It just can't be as stiff as a fixed caliper with that "C-Clamp" type of shape. If they used a shape more like a fixed caliper body for the body of a floating caliper, then they could be as or nearly as rigid. The problem comes from the sliding mechanism getting in the way of doing that.

 

[mrlocksmith]

After thinking it over I got a set of Poly Performance Axels, That should take care of things for now.


Mark

 

[Tinker]

Mark -
You'd better check the load capacity of the SF bearings. Remember, there is only 1 per side. I had a 1/2T 9" under my '56 F100 with a 10x8' glass rack & equipment body & an SCCA Mustang racer customer commented that the bearings wouldn't hold. Turned me onto an aftermarket supplier who custom-made new axles with 3/4T bearings that fit the original housing. Would not have been funny to lose an axle on that beast.

My FF was about $550 from CruiserParts. I asked them for a rebuildable (didn't care about r&P, just housing) 3rd, & they threw in a good one for about $50. Course shipping from NH to CO was steep.

NT -
What say you about the prop valve only controlling the pressure spike? I got this from Cliff at TSM & Wilwood used to make their prop valves.

 

[mrlocksmith]

I know there is a chance that I will eat up a few bearings. Keep in mind I only put about 4K on this a year, It is not a DD and it looks like replacing a bearing it not that big of a job if it goes out. So I think this will work for me. Especailly since I wanted a quck fix as I am off to Dirty Toy School in less than three weeks.

Mark

 

[5280Hawk]

I was just talking with a couple guys last night about how cool it would be to convert to coil springs on a 60 series. Be a helluva lot of work though...

There's a Build thread in here of a guy doing this very thing

Here

He'll have Coils and E-lockers front and rear when hes done.

 

[Spook50]

Spooky -
The mini-hub adapter you're talking about only works on a 40. I made a pair, had 'em powdercoated, & found out the holes don't match up to my 60 FF. So then I talked the guys at TSM into making a pair (I'd done all the measuring & drawing, & they already had 1/2 of it done with their SF brackets like you have).

So I have the prototype pair of TSM 60FF to 60 front caliper brackets sitting on the axle in my shop. I'm high-centered on making backing plates (some guys even take their front ones off, I know). But as soon as I finish a big job at work I'm back on 'em.

Yeah I'm not worried about the piston size for the 60 series calipers on the back, since I have a 1" bore MC right now and will have a 1 1/8" bore MC when I eventually get around to doing the hydroboost setup (only thing really holding me back is getting the hoses made up and finding out if/how I can mod the 62 PS pump for higher volume output), so I'll easily be able to move enough fluid for those and my 4Runner front calipers.

My biggest thing with the discs on a FF is that I want to use 60 series calipers, and lose these GM ones. I think the 60 series calipers would be perfect for the application and I'd have the benefit of keeping it as much Toyota as I can.

You say the modified 60 series knuckle housings didn't work with a 60 series FF axle because the holes didn't line up. Were they close, or were they far enough off that new holes could be drilled and tapped once the proper clock position for the caliper is figured out?

 

[Tinker]

Spook -
The holes were nowhere close. TSM should have the new brackets on their site pretty soon. I'll ask them when I go up there, prolly about a week or so.

The 60 calipers in the rear will be too big for the 4runners in the front. That's why I'm looking for smaller ones to fit my new brackets & rotors. The prop valve doesn't solve the problem, just the immediate pressure pressure spike when you first apply the brakes. I'm going to a Supra (1-1/8"?) MC so volume won't be the problem.

A GM Saginaw PS pump is adaptable & you'll get all the pressure & volume you could want. The one on my Vortec even looks like a 60 PS pump. Some links: https://forum.ih8mud.com/60-series-wagons/246273-power-steering.html & https://forum.ih8mud.com/60-series-wagons/173393-power-steering-pump-dead-need-your-help-2.html

 

[Spook50]

Spook -
The holes were nowhere close. TSM should have the new brackets on their site pretty soon. I'll ask them when I go up there, prolly about a week or so.

The 60 calipers in the rear will be too big for the 4runners in the front. That's why I'm looking for smaller ones to fit my new brackets & rotors. The prop valve doesn't solve the problem, just the immediate pressure pressure spike when you first apply the brakes. I'm going to a Supra (1-1/8"?) MC so volume won't be the problem.

A GM Saginaw PS pump is adaptable & you'll get all the pressure & volume you could want. The one on my Vortec even looks like a 60 PS pump. Some links: https://forum.ih8mud.com/60-series-wagons/246273-power-steering.html & https://forum.ih8mud.com/60-series-wagons/173393-power-steering-pump-dead-need-your-help-2.html

I would've thought the 60 calipers would be just fine with the larger 4Runner calipers up front, as long as you dial in the correct pressure differential. Are you referring to the stock LSPV when you talk about a proportioning valve, or any prop. valve? Right now I use an adjustable valve I got from Wilwood, due to the huge bore of the GM calipers I have on the back. If I dial it back a ways to keep it from sending full pressure to the rears, I have a much firmer pedal feel and the brakes are far more effective.

I take it TSM's FF kit still uses GM calipers?

I know alot of guys use a Sag pump in their 60s, but aren't the OEM 60 and 62 series PS pumps different enough so that you can't use a Sag pump in a 62?

 

[Tinker]

Spo -
60/62 calipers are too big for the rear. The Wilwood valve only dampens the pressure spike, so you can still lock up the rears in a panic stop (which evidently is not good according to the brake gods). Check out Braking Systems in Plain English

TSM still sells the kit with the GM calipers. Maybe they'll start selling the brackets they made for me that fit the 60/62 calipers. I feel I have to use them since they've been so nice to me. Just hoping I can find some smaller calipers to avoid the lockup. Your only problem is the park brake, no? You could remove the cables & go with the new TSM tcase disc park brake: FJ 60 Land Cruiser I am an unpaid shill for my fellow Castle Rock businesses.

Dunno about the differences between a 60 & a 62 pump, just know a Saginaw would do you fine.

 

[ntsqd]

snip.....

NT -
What say you about the prop valve only controlling the pressure spike? I got this from Cliff at TSM & Wilwood used to make their prop valves.

It may display that function, but I am unaware of any such design intent. It is intended to operate as a pressure percentage regulator. The guy in the office cube next to mine had the project of reverse engineering the original Kelsey-Hayes design and trying to come up with other pressure percentages beyond the knee point. (The adjusting knob moves the knee point, it does not change the percentage.) The math involved got very ugly, very fast. When that Engineer moved on the project went dormant for the rest of my stay there. No idea if they ever revived it or not.
P-Valve Knee point illustrated:

Some further reading:
Hydraulic Brake Components: master cylinder, caliper, proportioning valve
StopTech : Balanced Brake Upgrades (same author as Tinker's link above, and same author as the book I suggested somewhere.)

Spook-
The rear brakes do less initial work than the front brakes in a high speed stop. In low speed or static position holding they do the same work. In high speed stops the weight shifts dynamically onto the front axle causing most of the work to be done by the front brakes. If you have rear calipers with too much piston size you run into the rear's locking up way, way, way before the fronts will. This is a dynamic thing, as the initial speed lowers the tendency to lock-up is reduced. By using a caliper with a smaller piston in the rear you get the basic hydraulic balance closer to something usable without a proportioning valve (p-valve). The P-Valve is really supposed to fine tune the system, not make up for gross unbalance. If you found the perfect rear caliper you wouldn't need the P-Valve at all. The odds are really against this, but it is worth trying for.

From observation the shorter the wheelbase of the vehicle the closer the front and rear piston sizes can be. That is counter-intuitive to me, but that is what I have repeatedly observed. In the 94" wheelbase of an Early Bronco (used to have one, am still on several related lists) the Ford Explorer rear disc brake system is a very good match to the stock front calipers or the larger T-Bird caliper upgrade (similar to the 4rnnr upgrade). I know the front piston size, but don't know the Exploder size, so mentioning them is of little use. And even then it probably wouldn't translate to FJ60/62's.

The thing that I repeatedly run into is folks not understanding how hydraulics work to multiply force, and that this is scalable. That is to say that if you increase the front caliper piston area by 20%, but find the increase in brake pedal travel objectionable so you increase the master cylinder bore by 20% that you are back where you started. Both sizes have increased the same so the system leverage is the same as the starting point.

 

[Spook50]

Spo -
60/62 calipers are too big for the rear. The Wilwood valve only dampens the pressure spike, so you can still lock up the rears in a panic stop (which evidently is not good according to the brake gods). Check out Braking Systems in Plain English

TSM still sells the kit with the GM calipers. Maybe they'll start selling the brackets they made for me that fit the 60/62 calipers. I feel I have to use them since they've been so nice to me. Just hoping I can find some smaller calipers to avoid the lockup. Your only problem is the park brake, no? You could remove the cables & go with the new TSM tcase disc park brake: FJ 60 Land Cruiser I am an unpaid shill for my fellow Castle Rock businesses.

Dunno about the differences between a 60 & a 62 pump, just know a Saginaw would do you fine.

Hmmm, interesting. I do still think 60 series calipers would be better in my case than the GM ones I have on now, given that the piston bore on the GM calipers is HUGE (I'd have to measure, but I have a feeling the total piston cylinder volume on the 60 series calipers is still smaller than that of the Monte Carlo calipers, so moving down to 60 series calipers would be a step in the right direction). I do know that the 60 series caliper bore volume is considerably smaller than that of the 4Runner calipers I have up front now (which were a helluva nice improvement), though I wonder if there are any smaller-piston Toyota calipers that would easily fit over a 60 series rotor in the case of a rear FF axle. As it were, if I had 60 series calipers on the back, I'd still have far larger calipers on the front.

I've got the parking brake issue sorted out, now that the 60 series tcase ebrake setup looks to have been finalized (you said it was just down to sourcing the right size flange bolts, right?).

As far as the Sag pump, I can't find any reference to one having been put on a 3FE. I'd love to try one out, so maybe I'll make that a project for next Summer...

 

[ntsqd]

I don't have the numbers handy, but the actual diameter difference btwn the 4rnnr and the 60 calipers is not much. It was posted around here somewhere, but what I recall is that one set of pistons are the same size in each caliper. The other set in the 60 caliper are smaller, where the 4rnnr caliper has all 4 of the same size pistons.
The LA mini truck calipers use the same size pistons, I'm fairly sure, as the FJ60 calipers. Their difference is the rotor width for the non-vented rotor used on those trucks. So those aren't an option for most
According to http://www.toyodiy.com/parts/p_U_1982_TOYOTA_PICKUP_RN34L-KRA_4705.html the p/n's for the 2wd calipers that I've mentioned are 47730 (RH) and 47750 (LH)

The "Metric" (D154 pad, aka 'Monte Carlo' or 'S-10', or in the case of the p-brake versions the 'El Dorado') caliper uses a single 2.5" dia piston.
The 'GM' caliper (D52 pad) uses a 2-15/16" piston commonly. There is an oddball version of this caliper out there that has a slightly larger than 3" piston, but I've never seen one.

 

[Tinker]

Take the sum of the areas of the pistons in each caliper to make comparisons.

I was set on using the 60/62 calipers on the FF, partially for S&Gs, until I found the possibly heretical, & certainly counter-conventional-wisdom, factoid on the prop valve. But now, as NT says, I'm looking for a closer match.

Looks like snow today (wuss: don't want to work on our outside job), so I might get a chance to peek at my '85 & '89 HiLuxes for caliper thickness & bolt spacing.

 

[ntsqd]

Forgot to add that the 2wd caliper application that I looked up was a 1980 vintage. Looks like '79 to '83 used that fixed caliper. '84 and later apparently used a slider, which may be an option for those that aren't brake snobs like me. Their bracket bolts on like a fixed caliper.

I just measured my '86 turbo 2WD's vented front rotor and it is .880" (~22mm) thick. Lacking the time at work to jack up the front & remove a tire I can't get my dial calipers into the fender well enough to get a precise measurement, but the bracket for those sliders looks to have about a 110-120mm bolt hole spacing.

Curious thing when comparing caliper piston areas. For fixed caliper use one side's pistons only, for sliders use the obvious piston(s). The reason is that the pistons oppose each other in the fixed, but the back of the bore(s) of the slider acts as the "outside piston(s)". I mention the plural piston possibility in sliders because those used on some D60's are two piston sliders.

 

[HighPlainsDrifter]

Hmmm, interesting. I do still think 60 series calipers would be better in my case than the GM ones I have on now, given that the piston bore on the GM calipers is HUGE (I'd have to measure, but I have a feeling the total piston cylinder volume on the 60 series calipers is still smaller than that of the Monte Carlo calipers, so moving down to 60 series calipers would be a step in the right direction). I do know that the 60 series caliper bore volume is considerably smaller than that of the 4Runner calipers I have up front now (which were a helluva nice improvement), though I wonder if there are any smaller-piston Toyota calipers that would easily fit over a 60 series rotor in the case of a rear FF axle. As it were, if I had 60 series calipers on the back, I'd still have far larger calipers on the front.

X2

Why not upgrade the front brakes and use the old front ones on the back? Like maybe some four-runner brakes up front.
I'm still leaning towards the 80 series rear.....

 

[Spook50]

X2

Why not upgrade the front brakes and use the old front ones on the back? Like maybe some four-runner brakes up front.
I'm still leaning towards the 80 series rear.....

That's exactly what I was planning, except I already have the 4Runner calipers up front (nice upgrade, BTW). If i can find the ideal size for my rears, it'd be great, but at this point it looks like the GM calipers are certainly the most common choice, though the 60 series might be better due to piston bore volume (the 60 series ones having less than the GM ones). Although from the sounds of it, the 60 series calipers wouldn't be the ideal way to go in the back as far as overall brake performance and best proportioning between front and rear.