fjs0001

I bought a used, setup diff with an OS Giken and 3.3 gears from a fellow member. I finally got around to installing it and it leaks from around the pinion nut, not the pinion seal. Has anybody else had this issue before?

fjs0001

I found the nut loose. I put red loctite on it and torqued it to 125ft-lbs. I'm keeping my fingers crossed that it works.

SpartanSV

Considering the value of the components in that diff it would be a good idea to pull it out and inspect. These diffs use a crush sleeve to set preload on the pinion bearings. You can't just torque the nut to XX ft lbs and know that the preload is right. If the preload was set properly when it was built and the nut is now loose then you could have a serious issue with the pinion bearings.

soot

Common reason why that pinion nut would have loosened in the first place is if that crush sleeve had deformed further from a heavy load or shock. I've seen this more in Jeeps/4x4s that the diffs faced a lot of abuse. Once that sleeve has been crushed once it is really difficult to get the preload correct again. They are considered a single use part.

I do nearly all of my own work, but I send my diffs out to other people because of the precision and tools needed as well as the massive amounts of time it can take an inexperienced person to complete the work. I also recommend replacing your crush sleeve with one of these spacers from Weir since it makes setting the diff up a bit easier and makes it stronger than a setup with the crush sleeve.

At the very least check that the backlash and preload rotational tq meet factory spec.

edit: just realized this is a giken and 3.3s. Take it to a good shop, sounds like it was set up wrong by the PO or their tech. If that nut was loose who knows what else was done wrong. It's not worth gambling with parts that cost that much.

fjs0001

The previous owner told me his diff builder said to torque it to 125ft-lbs. I had to pull the motor to replace the boundary engineering oil pump seal, and I did a 6 speed swap with a new SuperMiata puck clutch along with swapping the rear diff. I've been driving it back and forth to work to see if I like the 3.3 gear ratio and to give the car a shake down. The diff definitely whines, but there are countless threads on miataturbo about the 3.3 gear wine. The wine goes away above 50mph and is loudest when deaccelerating. It's a little annoying first thing in the morning with the top up, but after work with the top down, radio blasting, and exhaust humming, it's not bad. Before I installed the diff, I noticed that the ring gear had tooling marks from when it was made. I believe those tooling marks are the main cause of the whining. I'm still trying to decide what I want to do. Next week I'll drain the diff and inspect the oil.

technicalninja

Proper installation of the pinion requires slowly tightening the pinion nut while you check the rotational torque of the pinion itself.
Tighten, check rotational torque, tighten again, recheck and so on. I've been doing this **** for nearly 40 years and I would NEVER spec a specific torque for the pinion nut.
When the rotational torque is correct that is what the final pinion nut torque is. It might be 30 lbs, it might be 150 lbs, and it will be different for every single rear end you build

The pinion rotational torque is measured with the carrier and ring gear OUT of the case.
You set pinion rotational torque FIRST when you are doing a final assembly.

You set up gear patterns and back lash before the final assembly (and I re-use the original crush sleeve for this mock up).
Set your tolerances up first because sometimes, especially if you are changing the gear ratio you have to change the pinion shim which is between the pinion itself and the rear pinion bearing.
Setting pinion height is the hardest part of a rebuild. Pulling and reinstalling the rear pinion bearing off can be a PIA!
You don't have to set final pinion rotational torque during the shim/backlash/pattern checking portion of the build as it doesn't matter yet. Having the pinion merely clearance free is all you need.

After ALL of your shim selection, back lash adjustments are done you take everything apart (except that bastard rear pinion bearing, you're done with that puppy now!) and start the final assembly.
First thing of final assembly is to set pinion rotational torque...

Anyone who says "Just torque it to XXX" doesn't understand this process...

fjs0001

I'm going to purchase the tools to check everything out on the diff. I need them anyway because I need to change the gearing in one my Jeeps.
Have you had any experience with this setup kit? I keep reading positive and negative reviews.
The more I drive the Miata, the quieter the whine gets. I can't even hear it with the top up on the interstate unless I let off the throttle. Even then it's very faint.