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Ring & Pinion Advice

T

texarback

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I searched but could not find an existing thread that applied to what I am doing.

What I have:

1) 1974 Front Differential - DANA 44 10 Bolt 8-1/2" Ring Gear & 26 Spline Pinion geared 3.07
2) 1974 Rear Differential - GM 12 Bolt 8-7/8" Ring Gear & 30 Spline Pinion geared 3.07

What I am doing:

I have completely restored the axles and have purchased new bearings, shims, seals, pinion nuts, etc. The carrier and the ring and pinion are original.

What I need to know:

Should I buy new rings and pinions.

Backstory on why I'm asking the questions. I've been able to get the diffs put back together but the patterns never seem quite right. I made the mistake of not measuring backlash before disassembly and so I don't know exactly what it looked like numbers wise as original. So, I have a relative who has been a mechanic and shop owner for 40+ years and I asked him if he would help me get it all sorted out. After going through everything he strongly recommended replacing the rings and pinions. His view is that the existing (original 50 year old) gears have worn together and since I don't know what the original numbers were, by replacing the bearings, races, etc. it will be almost impossible to have them match up exactly as they were. He thinks there will be noise and "could" result in metal flaking and additional wear that might undo all the new stuff I'm using. Thus, in some undeterminable mileage I could be back inside both diffs replacing everything again plus the rings and pinions.

I should also mention that both ring and pinion look to be in good condition. No overheating, warpage, chipped teeth.

I've looked at the YouTubes and many forums and this has been the first time I've seen this view expressed.

What do you guys (and gals) think?
 
wouldn't you have the same problem with new since you don't know their numbers?
 
If you used the same shims it should be very close to original. If your back slash and pre loads are in spec. You should be good. But with our seeing this odd pattern, can't say for sure.
Not sure I would stay with 3.07 even on a stock tire. Probably do the math on some 3.73 or 4.1
 
If the gear ratio is suitable for your application, just reset the differentials to factory specs with new bearings.

For the extra $$$ I would make solid crush collars....
 
fourwheelerjeff said:
wouldn't you have the same problem with new since you don't know their numbers?
Click to expand...

I don't know. That is why I'm asking the question. That question did cross my mind though.

Blue85 said:
Here's another thought - why would you want 3.07 anyway?
Click to expand...

I don't know, why would I? I don't know anything about gearing and the effects it has on driving. This Jimmy isn't going to do anything other than drive to Sizzler on Friday nights. I might run it down the highway a time or two a year. I did ask my relative about it and his opinion is staying with the 3.07 is fine based on my description of activities. Plus, I am restoring the vehicle to original specs. I assume that if it was good enough back then than it is good enough today. Maybe not.

Wes Harden said:
If you used the same shims it should be very close to original. If your back slash and pre loads are in spec. You should be good. But with our seeing this odd pattern, can't say for sure.
Not sure I would stay with 3.07 even on a stock tire. Probably do the math on some 3.73 or 4.1
Click to expand...

I do have all the original shims. On the rear, the two cast iron shims leave me a backlash of 17 thousandths which is way outside spec. I have not played around with the front yet so I don't know what the actual results are for using the original thickness shims. I did get the rear diff reassembled and using a shim pack the backlash was 7 thousands but I just never could get the pattern to look right.
 
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Yes 17 is way to much. Now I haven't opened a 12b in a long long time. Are the cast iron shims between the axle housing and the bearing or the bearing a Carrier.
Are the shims the same thickness? Could they be backwards ?
 
On the rear the shims are between the housing and bearing. 100% they are not backwards. I should note, I don't know if anyone has ever been in either diff. I'm making a large assumption that everything is/was factory.
 
What size tire are you running? 3-speed automatic?

If you don't know how the gears were set up before, you'll have to just proceed as you would with new gears, except with the backlash being a little bigger. Reading the pattern is different, as you're trying to overlay it on the old pattern, rather than to set it somewhere specific. This should be easy to do since it's the same housing, carrier and gears. Do you have the old shims that you could figure out what was where by process of elimination? Changing the bearings and races has only a small effect on the overall setup, as these parts are machined with tight tolerances. Why did you want new shims and what was the original problem you were trying to solve?

The age of the axles isn't as important as the miles on them. If a bearing was failing, or the pinion nut was loose, it's possible the wear is excessive and that's why you can't get it to look right.
 
what are the carrier shim measurements, left/driver and right/passenger. Typically if your back lash is loose like yours you want to move the carrier toward the pinion.
 
Blue85 said:
What size tire are you running? 3-speed automatic?

If you don't know how the gears were set up before, you'll have to just proceed as you would with new gears, except with the backlash being a little bigger. Reading the pattern is different, as you're trying to overlay it on the old pattern, rather than to set it somewhere specific. This should be easy to do since it's the same housing, carrier and gears. Do you have the old shims that you could figure out what was where by process of elimination? Changing the bearings and races has only a small effect on the overall setup, as these parts are machined with tight tolerances. Why did you want new shims and what was the original problem you were trying to solve?

The age of the axles isn't as important as the miles on them. If a bearing was failing, or the pinion nut was loose, it's possible the wear is excessive and that's why you can't get it to look right.
Click to expand...

I'll start with why.

I'm fully restoring the Jimmy back to original (or as closed as I can get it.) I have a build thread and have written about the rear diff.

I'll be running normal AT tires on original spec rims. It is a 3 speed though the transmission was shot when I inherited the truck.

Both axles have 170K on them and were covered in mud, grease, etc. I got them cleaned up and painted. I pulled the carrier and pinion in order to do the cleaning. While I had the diffs out I went ahead and put new bearings on and also changed the bearing on the pinion Timken was on there and Timken is what I went back with. On the Dana the oil seals were shot. Basically my goal was to make both axles factory fresh.

Wes Harden said:
what are the carrier shim measurements, left/driver and right/passenger. Typically if your back lash is loose like yours you want to move the carrier toward the pinion.
Click to expand...

Rear Axle: I used the original pinion shim and then the two shims for the carrier are cast iron. Here are the measurements:

Pinion original shim was .242
Passenger side shim was .248
Drivers side shim was .230

Putting the .230 shim on the pinion side leaves a way out of spec backlash. Obviously putting the .248 shim on the pinion side makes it much worse.

Again, this thing might have been out of spec before I started. I don't know the history. But, going back with the shims that came out does not result in a desirable situation.

I've not messed with the Dana yet.
 
What I am hearing though is I don't need to buy new rings and pinions if the ones I have now are not bad. If I can get everything set properly then everything will work as mechanically designed.
 
With out seeing the gears is hard to say. We did have a member here in last few months unable to get a good pattern, new gears solved the problem.
switch the shims, and see what your back lash is, and leave the pinion alone. I guess I am going to have to look at what a 12b needs .242 pinion shim doesn't sound right to me at the moment.
 
Thanks Wes.

If I were going to buy new rings and pinions what would you suggest? Brand? Site?
 
Dana Spicer, Yukon, are a couple I have experience with. GM oem would be the best, but $$$ if available. Be sure to get new ring gear bolts, don't reuse the old ones. just a reputable supplier. A few Vendors members here might be to set up, check our vendor section.
 
Well your relative and i are about the same years in experience. I am closing on 50 in the trade. Now though I try to stick to my toys, and skip all others.
 
Can you get us a picture of this pattern that you are getting, it’s a little late now but I would never change carrier or pinion bearings just to change them. They live in an oil bath and unless they are making noise or loose I see no need to get yourself into the situation you are in now.

I have put many diffs together using the original shims in the original locations and been very close on the numbers that’s why I am confused about this odd pattern.
 
Maybe it’s important to mention the Jimmy was pretty much worn out and I’m doing a complete frame off restoration. This isn’t a vehicle that I was driving around and just decided to dive into the diffs. The Dana was pretty bad when I cracked it open. The back, wasn’t horrible.

At any rate, I appreciate the feed back.

I’ll throw some more pics up of the actual Rs and Ps this weekend.
 
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