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Discussion Starter #1
I have seen guys on various forum look for used differentials and want to upgrade a C2 to posi if it wasn't so ordered.
Many don't realize the differences in the units in both the housings(carriers) and the cases( posi unit)

In order to help those who may buy something they may regret I'm running some info here to help you ID them.

The 63-79 iron units will mount in all the years but the early ones should not be considered unless you are into the correct date coding. The later C3's had better cases.

The housings in the 63-64 used I believe a Dana case and they were weak. Most by now have been replaced with the common Eaton 3 series case,which GM switched to in '65

If you look to buy a used unit to put in your car be sure to check it good.

Here is a 64 carrier and the dimension between the bearing pads.





Here is a 69 carrier and you can see it is wider. This is important for shimming the backlash. The kits on the market do not have the thin shims needed for the early units. I have to buy a full set and grind them to size for setup and final preload. That's why the kits are advertised starting with 65. Now to throw a curve in here, I have a 66 unit that is also narrow like the 63-64's. Something like that will drive the DIY guy nuts trying to figure out how to set it up.





If you want more info let me know and I'll post it for you.
 

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Thanks for the info...Will take all that you can post. thats what its all about sharing and learning.
 

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ok I'll dig up some more pictures and post them for you
 

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ok, here some more pictures for you. Some of these I have posted before but just in case you missed them I put them back.

The 63 used 7/16-14 bolts in the front bracket. This is ok for a correct resto but again I would stay away from the 63-68 diff if you have a choice.





The question comes up a lot on gear ratio and case series. The 273,308,336,355,370,373,390,and Tom's 411 and 433 all mount to a 3 series posi case. The GM 411, 456, 488 mount to a 4 series. The difference is the thickness of the flange for the ring gear. Here are a 3 & 4 series. The 4 series has the ring gear and is setup stock with the posi springs.





This WAS the diff in my son's 75, Notice the teeth marks on the case. I polished them and radiused them. You'll also notice I set them up without the springs and plates. This was a 373 gear and it was quiet as a stock gear. Sometimes with HP gears you may get a little gear whine, in my 72 with 336's I set it up great but have a little whine in the 60-65 mph range.





After 3 years of abuse, the diff couldn't take 200' burnouts anymore and blew up. I have another post with more of these pictures if you want to see total destruction.





Ok back to diff options.

Here is a custom sleeve my buddy Norval makes for his jobs. It is solid and holds up great. I also use them if requested only mine are drawn down tubes.




Here is a stock type aftermarket sleeve. I used to have the GM sleeves and they were better,made from thicker wall tube but they are obsolete now. I sold the last one I had last year for $8- good deal.




If you're going to pull a diff out and you're like me and don't have a lift, use this sissors jack from HF. They cost about $60 but sure make the job easier to do.





When buying a used diff, know which pinion yoke you need. This is a small yoke but there is also a larger yoke. measure the distance from cap to cap on the DS joint.




Also when buyng a used diff bring some brake cleaner with you can shoot the posi case cross shaft hole and windows. wipe them down clean and do it again. Look for the cleaner to stay wet in cracks. If you find one cracked it's junk, forget about trying to repair it or you'll have a diff like the one above in pieces. The 65-68 are known for this problem, they have a little square windon in them compared to the "tear drop" window of the 69-79's.








How/s that? If you look up my post on rebuilding these you'll find some of these and many more pictures of the work.
 

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I liked your tip on using Lucas 85/140 oil. When it comes to differentials you are the man.

What is involved in swapping out a 1330 pinion to a 1350 pinion yoke?

Thanks
Chuck
 

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Gary,
Have you used the adjustable pinion sleeve from Ratech or is it Rateck?? and do you like them....I once had some diffs rebuilt by a guy whose father was a famous Corvette racer and friend to Tom (from Toms diff). Toms taugh the son to do rearends BUT he did NOT use any pinion sleeve when he rebuilt mine...I got concerned and called Toms..the guy who answered the phone listened to me and said "NO sleeve air man air".....honest

Howard
 

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Discussion Starter #8
Swapping a pinion yoke isn't bad out of the car but a little tricky on the car. Just follow the same procedure for replacing the pinion seal, in fact change the seal at the same time. If out of the car I use a 0-30 in/lb dial TW to check the present bearing preload and return it back there with the new seal/yoke. Also look at the yoke OD that mates with the seal of there is a wear groove then you can get a speedy sleeve. They are about $30 and not stocked most places. I have to order 4 -5 at a time.

Howard,
I had that same conversation with Tom's late son several years ago. I don;t recall the reason they went without the sleeve? I would think under impact load of a drag car if would be a problem?
I use the Ratech sleeve kits. I think they could be better packaged for $45. They come with a couple of shims but everyone I installed I had to use a surface grinder to dial them in to the 15-18 in/lb range. There was no way the kit shims were going to work. The ones I sold outright I told the guys they'll need to fit them as well. It's a little deciving the way they are advertised.
 

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Gary,
In Chicago there is a company called Chester Brothers they used to do stock car rear ends (now they make staples all day), Eddie Chester is the one who told me I should have a pinion sleeve, he thought I should measure the crushed sleeve and replace that with a piece of thicker wall tubing cut to the exact measurement...we went with whatever was available from GM in 1995.....................Howard
 

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Swapping a pinion yoke isn't bad out of the car but a little tricky on the car. Just follow the same procedure for replacing the pinion seal, in fact change the seal at the same time. If out of the car I use a 0-30 in/lb dial TW to check the present bearing preload and return it back there with the new seal/yoke. Also look at the yoke OD that mates with the seal of there is a wear groove then you can get a speedy sleeve. They are about $30 and not stocked most places. I have to order 4 -5 at a time.
I have a 69 rear end for my car. It has the smaller u-joint. Is the wider u-joint yoke available to fit the 69 size pinion? Or should I go to the newer model C3 rear end for maximum strength.
 

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Discussion Starter #11
The 69 still had the small yoke on the pinion. You can use the larger yoke on the pinion but will need the conversion joint. I think Spicer makes them but I don't have the number. Not sure just how much you're going to gain with it.
 

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The 69 still had the small yoke on the pinion. You can use the larger yoke on the pinion but will need the conversion joint. I think Spicer makes them but I don't have the number. Not sure just how much you're going to gain with it.
I have the Auto Gear M22 with a 400 Large front yoke. A larger Later C3 Driveshaft and the small yoke on the differential. So now I have a large U-Joint at the front of the diveshaft and need a conversion U-Joint for the rear. That is why I would like to convert to the large front yoke but the later model yokes don't fit the Pinion spline on the rear end. Really I guess I am looking for a transitional or conversion Yoke? I think there is one available but where would I look? The second part of the question, is the 69 small yoke differential as strong as the later C3 differentials with the larger yoke and pinion shaft?
 

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Discussion Starter #13
The very early 63 ran a different spline pinion, you still have that one? I'm doing a 63 diff now and used the typical gear set with it, I have the small yoke on this one but the large one would have fit as well. Do you still have the early 63-64 posi?
You can try Tom to see if he has one of he conversion yokes if you just want to stay with what you have.
The pinion shafts are all the same from mid 63- 79. The larger joint may be stronger but usual failure is within the diff rather then the pinon yoke.
 

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there is a combination u-joint.....Spicer 5-134X as I remember BUT check/measure before you buy.
...redvetracr
 
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