74' Rear Diff Fix (1 Viewer)

[LR LC200]

All- Getting a significant howl out of the rear end now. I had to open up the diff to remove the half shafts as part of a 4 wheel disc conversion. In that process I had to adjust the diff center section to the left with those silver adjusting "cups" in order to bring in the passenger halfshaft to align the rotor with the caliper. So suspect that change has misadjusted the mesh of the gears, hence the howl. I'll crack the pumpkin again to see if I can adjust right some more, but there's a limit with fixed caliper mount vs. shoes seated in a different section of a drum.

When draining, lots of metal "flake" on the drain plug magnet. Giving you all of this background to say... I probably need a diff rebuild. How have folks approached this in terms of sourcing the gears, runs,and bearings?

I'm also told adjusting without the right instruments, is high risk....

Thanks,
LR

 

[snaggletto]

Give Cruiser Outfitters a call. They have geared third members that should just drop in.

 

[B y r o n]

. . . In that process I had to adjust the diff center section to the left with those silver adjusting "cups" in order to bring in the passenger halfshaft to align the rotor with the caliper. . . .

I've never heard of adjusting the center section to align the caliper and rotor, this is normally done with shims or spacers at the mounting brackets.

Depending on how much damage you've done to the gears you may not need a complete rebuild. You do however need to pull the third member and inspect before resetting the gears for the proper pattern. Yes, you need the proper gauges and tools to adjust it properly.

 

[JackA]

I've never heard of adjusting the center section to align the caliper and rotor, this is normally done with shims or spacers at the mounting brackets.

I have never heard this either.

 

[shawnfj40]

No this is a new one. My guess is there is more to this story.

 

[lc69hunter]

I've never heard of adjusting the center section to align the caliper and rotor, this is normally done with shims or spacers at the mounting brackets.

Depending on how much damage you've done to the gears you may not need a complete rebuild. You do however need to pull the third member and inspect before resetting the gears for the proper pattern. Yes, you need the proper gauges and tools to adjust it properly.

Same here. I just did my rear disc brake conversion last weekend, and all I had to to was pull the pin to get to the C clips, pull them, and then pull the axles. Putting it back together was just the opposite. slide the axles back in, jiggle them to get them to mesh, put the C clips back on, the re-insert the pin. What do you mean by adjusting the center section?

 

[Rock40]

By adjusting the side to side mesh of the ring gear to pinion gear, you have undoubtedly shredded your differential. NEVER do this. Toyota set up the backlash to be correct from the factory and if you swap gears or add a locker, the backlash needs to be set up again with the correct tools. In all likelihood, you forced the ring gear up against the pinion gear very tightly which caused a ton of heat and friction to occur while driving. Pull it and start over with new/used one.

As others have said, what you did was likely unnecessary for your disc brake install. When I had factory axles, I also did rear discs with zero issues. Just have to pull the C-clips and go from there during the bolt-up.

 

[shawnfj40]

Yes it's a pretty straight forward install. You might be money ahead to find a used factory third member. Unless you want to learn to build one yourself. The tools are not that expensive and you can get them at most any tool place.

 

[LR LC200]

All- Guess notifications went to my junk mail, so just seeing this.

As many of you have suggested, this disc job should have been straight forward. In my case the adjustment of the diff mesh was so far to the right that once the pin was removed exposing where the c-clips are, I could not get the left one out. This was due to the drivers side half shaft not being able to be pushed towards the center enough to remove the c-clip. I eventually had to unbolt the two large bolts on the left side in order to adjust the left side cup outward enough to free the c-clip.

Note the metal shavings or flake were present when I first opened up the diff not as a result of the subsequent howling although that would surely make it worse if I drove it that way.

So best case is I only need to replace the bearings as they are visibly pitted and have the mesh adjusted by a shop that has the correct tools...

Worst case is what I have planned for, which is: replace pinion, ring gear and all the bearings, plus the proper adjustment.

Apparently all that had the disc conversion did not have the existing wear that I had and therefor the adjustment was more in the middle allowing easy removal of both c-clips and alignment of disc mount/caliper/rotor.

Pinion, ring, bearings, and install kit are inbound and shop selected for rebuild at $250 in labor.

I'll let you know how it goes.

Thx,
LR

 

[LR LC200]

Ok- New gears installed professionally, housing sandblasted, primed and painted, but... even with new gears the adjustment is to the right as you can see by the number of exposed threads on the adjusting cups.

So I may still have my original issue of not being able install the c-clip for the left half-shaft and the second issue being the right half shaft too far outboard to align the rotor with the caliper.

Turns out, the center section has been retrofitted to what we think is a standard truetrac diff.

Trying install tomorrow. Might be looking for solutions to the above issues. Might have to go back to rear drums or replace the whole center section with something more adjustable.

 

[LR LC200]

Think one of two issues are manageable. Think I'all be able to punch in left c-clip, but will need to mount right caliper mount on outside of axle shaft flange and see if that works...

 

[Rock40]

Maybe the angle of the photo make it look weird but you should be able to get that left C-clip in place. Wiggle it in or try popping it lightly with a hammer. Just be careful about breaking it.

 

[sadam_husain]

there is something wrong if you have to wind the diff centre so far over that you don't have enough clearance to fit the C clip, I'd be backtracking to sort it out and get everything to fit properly the way Mr Toyota made it to fit

 

[LR LC200]

Ok got it to work. Tapped in clip. Getting it back out in the future will be a different story...
I ended up needing to use M-12 spacer washers over each stud under the rotor to bring it outboard. Will need to get longer studs when I go to alloy wheels.

On to next challenge: Disc brakes work great but rears lock up first. Been reading about proportioning valves, but what's to prevent me from just switching the lines so the greater output goes to the front? FJ80 MC that came with kit below:

 

[LR LC200]

BTW, agree with ur Toyota design comment. The disc kit is the first thing I've done that's not OEM or OE. The aftermarket diff was installed by PO.

Thanks,
LR

 

[Rock40]

Don't do something crazy like swapping the front/rear lines. Yes, the rear discs lock up first because the discs you have now are way more efficient than the front drum brakes. Do it correctly, install a residual valve and an inline proportioning valve and be done with it.

 

[B y r o n]

Ok got it to work. Tapped in clip. Getting it back out in the future will be a different story...
I ended up needing to use M-12 spacer washers over each stud under the rotor to bring it outboard. Will need to get longer studs when I go to alloy wheels.

On to next challenge: Disc brakes work great but rears lock up first. Been reading about proportioning valves, but what's to prevent me from just switching the lines so the greater output goes to the front? FJ80 MC that came with kit below:

View attachment 1350870

You need to know the exact part number of the master cylinder they sent as there are a couple variations of them. I used what looks like the same master in my conversion but I have 4 wheel disc not drum front disc rear. You definitely don't want a master setup for ABS.