I'm setting up a new diff and 4.77 gears.

As this is the first time I have done this I am taking extra pains to try and get it right.

Attached are a couple pics of the pattern on the gears.

The first pic is a close-up to better judge the depth. The gear paint makes a ridge where it is pushed down by the pinion, and kind of makes it look like the pinion is going deeper than it actually is.

On the second pic you can see both the drive and coast patterns.

The other pics are references showing acceptable, pinion too shallow, and pinion too deep.

Pinion bearing pre-load is at 13 inch lbs at 102 lbs of torque on the nut.

Backlash is at .004" checked in several places on the ring gear.

What do you think?

 

im looking at doing this soon as well can i ask where you got your carrior bearings/ rebuild kit?

Based on the diagrams and what i see its not too bad but i havent exactly set lash on anything yet either so my opinion on it only has so much weight lol. how long did it take you?

z

 

The toe is the inside edge, the heel is the outside edge. It looks to me like you are just slightly too deep.

 

Monkman is right, after looking at it again, it looks like your slightly too deep.

 

ahh i see now thats why its nice to have someone whos done it before.

z

 

btw...paint only needs to really go on a few teeth for measurement...and maybe on opposite sides of the ring gear. Putting it on every tooth may give peace of mind but it's a little overkill imo.

 

You nailed it with "peace of mind"

Actually though, I only painted it in two places originally.

After going through this a few times the paint has spread around.

 

Thanks afgmoto1978 and monkman.

I thought it a little too deep, but lacking experience with this job I needed some more opinions.

The pinion spacer was changed from 3.35mm to 3.20mm, which is actually the stock spacer. It looks good to me now.

 

So I got the backlash set, 3.5 - 4.3 all around the gear, everything torqued down properly, checked and rechecked.

Installed the diff, put the halshafts in, drive shaft in, and put a jack under the lower arm so the shafts are up off the subframe.

Also, I did put oil in the diff first.

Started it up, ran through the gears about and it was apparent something is loose.

Shut it off, crawled under the car and I can easily twist the driveshaft much more than should be possible.

It's like the backlash opened up to 1/8" or something.

Looks like I'm pulling the diff back out to see what I did wrong.

Any ideas why that might happen?

And yes, everything was all torqued down.

I'll post again when I figure out where I screwed up.

 

Get it out yet?

I am curious as to what happened.

 

there is a crush sleeve that needs to be replaced each time you... iirc , it is responsible for your preload. If it is too crushed, it won't hold the pinion properly.

 

Yeah, I think I made a mistake with the crush sleeve.

I know it needs replaced if you start over, I ordered a few extra.

I'm thinking the preload wasn't right. I have replaced the crush sleeve, reset the pinion preload - it took 165 lbs this time rather than ~100.

Previously the pinion was too deep and I put in a smaller spacer to move the pinion at .15 mm. I reused the crush sleeve that I had just put in previously, as it would need to be crushed a bit more. That is I believe the mistake.

So I followed the Mazda manual to the letter, replaced the crush sleeve, set it, pulled the nut and flange back off as per Mazda, installed a new oil seal and gradually tightened the nut back up to 166 ft lbs, which was what it took to crush the sleeve until I got ~14 inch lbs of pinion preload.

Re-checked the pinion preload - looks good at ~14 inch lbs.

Reset the backlash, lash is mostly from 3.5 - 4.5 or so. Couple of outliers at each extreme but just within Mazda spec of .0028 variance. Trying to fine tune the lash anymore would push the outliers out of spec.

Besides, the left side spacer is at 6.50 mm - that's the largest one made.

Oh, and the backlash setting was still ok when I removed the diff- I think the noise I heard was due to pinion preload - I will know later this week.
The lash just felt like it was open to much because I didn't take into account the size of the lever that the prop shaft represents.
It just felt like a lot.

A word of advice - should you try replacing the diff and the gears, it's a good investment to buy the entire set of spacers. (yeah, that's what I did)

I'll get it back in the car this week and go for a break-in drive on the diff and see how it goes.

Anyway, this has all been quite a learning experience.

 

Ok, got the diff reinstalled and ran it through the gears - sounded pretty good, as in any noise we could hear was coming from somewhere other than the diff. Some brackets that were not yet cinched down,etc.

Before I can drive it, on to the next problem.

You know the rearmost tunnel brace, the one that snakes through the PPF?

Yeah, that one. The mounts for it appear to be bonded to the top side of the tub in a pocket that is underneath the bins.

If you can believe it, the left side mount broke loose. There's still two holes there, but no threads. It had had only one of the threaded mounts in the hole for sometime, as the mount was skewed for some unknown reason.

Last night I took out seats, console and bins, only to find that that mount is between the 'floor' beneath the bins and the chassis.

Looks like I get to cut a hole in the floor there so I can access that mount and fix it in place.
I'm thinking put the screws back in it and then fill the pocket with epoxy and fiberglass.

Always something...

 

This was good stuff. I have to install a 4:30 in the next few months.
Thanks for sharing your effort.
Regards,
Crispy

 

^ I will be doing a complete writeup on this, once I have driven it a bit and know that I am actually done.

 

I just had a shop install the turbo II internals and a new 4.30 final drive. The car has a horrible jet engine whine when the rear tires start rolling and gets worse as the speed is increased. He said the ring and pinion pattern was set perfect. Any ideas?

 

Best idea: He's lying, or a bearing is shot.

 

The shop should have provided you with some numbers.

* pinion bearing preload in inch lbs
* torque required to set the preload
* backlash settings - min, max and average
* size of the pinion spacer used
* size of carrier spacers used

I'm guessing they didn't do that.

From what I've read of different noises that may emanate from the differential, the one you describe sounds like it is related to the pinion. As the pinion is spinning 4.3 times faster than the diff, the noises coming from it would be higher in pitch than noise from the differential bearings.

I would suspect preload, or as Monkman33 has suggested, the bearing is bad.

 

Well.. It was torn down twice and the second time a new crush sleeve was NOT used. Could that b it? Sorry for thread jack.

 

The question would be "What was done to it after the 2nd teardown?"

I tore mine down again after it was determined the pinion was too deep.

So a smaller spacer was installed, and I reasoned that as the crush sleeve would need to be crushed a little further, I could just re-use it.

That did not work. After installing the whole thing, it made too much noise so I removed the diff, went through the whole process again using a new crush sleeve.

I would suggest reading up on the diff procedures in the manual so you are more familiar with the process.

The crush sleeve is installed and crushed until the proper preload is obtained on the pinion bearings. The ft lbs of torque required to get it to that point are recorded.

Then the companion flange is removed, the oil seal installed, and the flange replaced at which point the nut is tightened back down to the recorded torque in ft lbs. I did the final assembly in increments, re-checking the preload as I went.

So, there may be cases where the crush sleeve can be re-used, but I won't be re-using any again. It's a $10.00 part - it's not a bad idea to have extras on hand for just such occasions.

I am no expert at this, just trying to pass on what I have learned during this project.

 

Makes. sense. It will be torn down a 3rd time. G

 

Let me know if you need assistance on this. I would suggest those mounting bossed be removed by drilling out the spot welds with a spo wel removal bit. That way I could weld in new clinch nuts and weld the mounting bosses back on the chassis. It's more work up front, but you may find getting to that recess from the inside will be a nightmare.

 

Thanks for the offer, but it's already been taken care of.

Removed the seats and bins, cut a hole above the mount and then put in a mount that was secured with a couple of 10/14 x 3/4 machine screws. The holes for the mount are threaded 8x1.25mm so it all just bolts up.

All told about an extra 6 hours of work I hadn't planned on.

All put together now. Just need to install undertrays and wheels and go for a test drive tonight.

 

Finally got everything back together tonight.

Put the new rain tires on and took a short drive to check out the diff and scuff the tires.

The new Carbonetics diff and 4.77 gears worked great. No new noises, the diff doesn't even make much noise.

No gear or bearing whine!

I didn't drive very fast, the roads are dry and I didn't want to mess up the rains.
Autox this weekend, so that will be the real test.

Now that I'm fairly sure I didn't screw anything up, I will write up the procedure when I get a couple hours to work on it.

 

Sorry for my ignorance , but Im installing a 4.444 diff one on my FD
How is the best way to adjust the preload on the pinion?
Cause in the Mazda manual just said that you should adjust the preload to 17lb and that's it.

Will appreciate if you can help me in that matter.