diffy rebuild

[azruss]

My diffy has developed some serious clunking when loading and unloading (accel/decel) if this makes any sense. It's a 71 with somewhere north of 275k miles on it. I was in it many years ago and it showed ring and pinion tooth wear at that time. I don't remember what I did to it other than perhaps replace bearings. I have mics, calipers, and dial indicators but don't have any of the other specialty equipment shown in the manual needed to set all the tolerances. Is this a job I can do at home or best left to the experts? I would also like to change it to a limited slip. I do not race the car, but installed a rear sway bar and the inside rear wheel likes to lift and spin in a hard corner. Traction Concepts has a LSD on ebay. They are out of Baton Rouge. Anybody know anything about them. Would love to get any input on this.

[vandor]

I have set up diffs without special tools, one just has to imrpovise. The clumk could be worn sungears, or parts in that system, the R&P may be ok.
I've had the LSD in my Spider that we sell and it works very smoothly.

[mscafide]

Think I have some shims I can send you, Will look for parts I have and will send do you, I will do nothing with this stuff and you will.

Free and I will pay shipping.

Mike

[azruss]

Thanks, Mike.
Csaba, the LSD on your website is for a 3.90 ratio. Would this work with a 4.10 or would I have to convert the entire dizzy to a 3.90. What components would I need.

[vandor]

It would work with any ratio in the 1968-78 diff housing, 4.3, 4.1, or 3.9. AFAIK the carrier is the same for all those.

[azruss]

Removed the ring gear, side bearings and caps. The rollers have a few ultra-fine radial scratches. they are very smooth turning in the race by hand. So now the problem is how to set the pinion rear thrust washer. I'm planning on buying an new 3.9 R & P along with a LSD. The book uses a dummy pinion for measuring the thickness of the thrust washer. I assume the purpose of the thrust washer is to position the pinion gears in the proper location in the housing. I'm thinking I can measure the existing pinion depth from the flange face and duplicate that depth with the new pinion and be good to go. Let me know if anyone thinks this is a bad idea.

[vandor]

I do not know if that will work, as we don't know how precise is the end-face of the pinion. I think if you look at how to calculate the right shim based on the number scratched into the pinion then you could possibly compare the number on the old and the new pinion and add or subtract the needed amount from the shim.
I *think* one can do that, it's been years since I've done it.

[azruss]

Think I have some shims I can send you, Will look for parts I have and will send do you,

Mike, I sent you a PM. Don't know if you ever got it. All my stuff is showing up tomorrow, so let me know the status on the pinion shims
Thanks,

[mscafide]

Russ

I have not found them yet. I have been creating new storage space and dumped things in boxes. As I sort through everything I keep finding NOS Fiat parts from the 70's.

A box with a pair of bearings which I think may be axel bearings p/n 4438573 but I can't trace the number to any parts book. I will get through this stuff as fast as I can.

Mike

[azruss]

Mike,
I did some calcs between the shim for the old pinion and the new pinion and it would require the same size. So I am using my old thrust washer. So i'm probably good to go. So no rush in searching through all your stuff.
Adjusting the pinion load was a real bitch. I hope I have it set ok. I'm currently out in the 100+ heat trying to get the backlash dialed in. After that i will be "bluing" the teeth to check the mesh. I've made a few tools for a work-around on the factory set up. If it all works out, I will post pics and the procedure I used, in case someone out there is as crazy as me.

[mscafide]

But "It's a dry heat" ha, ha. Just jump in the pool however the pool water is too warm too unless you have a chiller.
You live in hell.

I know the weather in summer can suck.

I may try to visit someday and if you come to South Florida feel free to stay at my house and talk car stuff, drink beer and eat.

Mike

[azruss]

Thanks, Mike. We set a new date high at 105 yesterday. Supposed to get down to the 70s in the next few days.
The diffy is now back together again. I posted details and pics on mirafiori.com (didn't have use a photo server to post there)
The mesh pattern looks close but is biased toward the edge of the tooth, so I may still need a thrust washer...specifically a .102-.104 and .104 -.106. Don't know how much change each size makes. The one in there now is .100-.102 (measures .101")

[azruss]

I took the completed LSD to a rear end shop and they said the mesh pattern looked good and go ahead and run it. So it's back in the car and took its first test drive. It really changes the handling of the car. Rather the just spinning the inside tire, the rear end now slides out with power applied to both wheels. It got me into trouble right off. All ended well and now I have to learn how to drive the thing without killing me or the car. Still need to figure out the speedo error.