I'm going to be rebuilding a differential to install a 4:30 R&P and other nice aftermarket parts. This is the last part of the FD I've yet to crack open and fiddle with. I have all bearings and seals ready to go.

So...any tricks or hints I should know about or that would help me before I delve in?

TIA,
Crispy

 

Just plan to spend plenty of time working on the shims. You'll need bluing.

Make sure you have a diagram of contact patterns to show how to change your shims based on the contact.

 

The book tells you pretty much wht you need to do. Make sure you take the proper measurements and replace the crush collar, bearings, and seals. You will need a pinion depth gauge and a tool to hold the flange when torquing the pinion nut.

 

Thanks guys. I'm familiar with bluing agent but I've also seen a white compound used for checking the gear pattern. I'm emabrrassed to ask what this white stuff is called?

TIA,
Crispy

 

Damn, somebody slept through sex ed!

I had an auto 3:90 diff for my project car and needed to put the 4:10's in it. I opened the diff up, took it apart, bolted the new ring gear on, then took it to a guy who has done hundreds of R&P setups. He charged like $75 to put it all back together, set it up right, all that jazz.

I think it's one of those skills that you have to mess up a few times before you really get comfortable with it. Personally, I don't want to go through the learning curve, I'd rather have someone else who knows it inside and out do the job.

The diff is a very typical diff as far as assembly/setting up. The guy who did it did TONS of diffs for 4x4 guys, they are into diffs all the damn time. I got the new parts for him, the seals, crush tube, etc. and he took it from there.

Dale

 

You don't know Crispy, he'll do it better than most his 1st time even if it takes all night

 

i suppose, but there is easy things to miss that aren't highlighted in the book sometimes, like preloading the carrier while getting a tooth pattern. sometimes it takes a few practice runs to know all the little niches. it's pretty easy to destroy almost everything if you aren't careful and slap it in, as you only get one shot(well that is unless you hear the groaning and stop immediately), if the gears aren't matched up right then it is quite easy to destroy a R+P as well as all your new bearings.

 

...and hence why I asked the initial question.

To some maybe. But if I took that attitude I'd never know how to rebuild a rotary and would still be resigned to simply changing the oil and brake pads. Give a man a fish feed him for a day, teach a man to fish, feed him for a lifetime.

Regards,
Crispy

PS...no one answered my question as to the white agent for checking gear engagement is?

 

i'm in the same boat, i would check the gear pattern before i pulled it apart, and then after.

i do have a friend that's rebuilt his FC diff a couple of times, the second time he gave it to an ex ford mechanic, and the guy put it together and told him what the backlash was, accurately, without measuring.

its definitely one of those things where experience isn't needed, but it really makes it quick and easy. since just about every ford diff has been rebuilt (at the dealership actually used to do the mazda B truck/rangers too), any ex ford mechanic knows how to do it.

 

Use a non-drying paint in white or blue to set backlash. When checking backlash put a load on the ring-gear when rotating the pinion. It's not difficult at all; sometimes it goes quick and others it takes a little more time. If you do a bad job you'll hear it...

 

You can learn enough on the internet these days to do anything, I didn't do a great job on my s10 rear ends years ago but it gave me the experience and with more learning and tools I did my rx7 rear end a couple times. Go for it. But also not a bad idea to let someone else do it, but I also had two bad experiences with other so called professionals who did a bad job.

 

these are much simpler than most, being a 3rd member diff with adjustable preload adjusters for the carrier. most difficult part is setting the pinion depth.

 

The fd has shims not adjusters like the older ones.

 

well that sucks, but at least the FD units don't need as much attention as the earlier clutch type LSD units.

 

The fd LSD units break and then we upgrade to the fc clutch type LSD..

 

usually i see the case break but that is a universal issue.

 

See if this helps:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/differential-setup-opinions-gear-pattern-890768/

 

I recall that thread. I even posted in it.
Thanks for reminding me of it.
Regards,
Crispy

 

check out my writeup on rebuilding a diff - still going strong after two full seasons of autox
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/fd-differential-remove-replace-writeup-897359/

 

That's golden....gratitudes my friend.

I have two diffs to play with, one for practice and one for "the money."

Regards,
crispy.

 

ive done it if you have any questions just pm me. the hardest part is pinion depth for sure

 

I bet over the years I've done 50 of the things (dana's, GM's, Fords, etc, etc); they all carry the same basics. The first several took forever to get right but eventually technique is the key.

Always remember these important basics:

• Everything clean, really clean. Bearings a light coat of engine oil for assembly and checking.
• Bearing preload - most important
• Drive tooth pattern
• Coast tooth pattern
• Backlash

As a start use the shims removed from the old ring and pinion and put them in the same locations.
Measure them and write them down.
Once you get correct bearing preload on the carrier always subtract the same amount of shim on one side as you add to the other when moving the ring towards or away from the pinion; this way the preload never changes.
The pinion depth is the biggest PIA but most necessary to get correct.
No real need for all the special tools just patience, time and read the patterns.
Sometimes you can get away with using the old crush sleeve for the pinion depth setup as long as the rear pinion bearing is well seated.
Make sure also that the bearing cups are seated in the housing; again cleanliness is vital to a proper cup install.
Also the patterns are a guide; no need to match them exactly.

Here are a couple of pattern guides that are a bit clearer than the workshop manual.
http://www.precisiongear.com/pgtechpatterns.htm
http://www.norcalttora.com/~dick/Dan...%20pattern.pdf

FYI Richmond Gear marking compound is white which I like the best. The blue, for me is harder to read. Yellow is acceptable also.

Hope this helps a little....