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Discussion Starter · #1 ·
Someone has changed the rear end on my 57 Truck to a 12 Bolt GM. The problem I have is that one of the axles sticks out about 1/2" further than the other. This is keeping the brake drum from covering the entire brake shoe. Any suggestions?
 

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Someone has changed the rear end on my 57 Truck to a 12 Bolt GM. The problem I have is that one of the axles sticks out about 1/2" further than the other. This is keeping the brake drum from covering the entire brake shoe. Any suggestions?
A 67-69 Camaro 12 bolt axle is 1/2 inch shorter than a 70 Camaro Chevelle if its a Car rear. Also if its a 30sp truck a 69 axle is shorter than a 70 but not quite that much.
 

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Discussion Starter · #5 ·
Well, I don't think they are switched, the one side fits fine. It has positrac so I'm assuming it's a truck rear end. I spoke with a friend of mine and he referred me to a performance shop close to me that said they could shorten and re-spline the shaft. Thanks for the responses and the suspension chart is just what I needed. If I can figure out which one I have maybe it will be cheaper to just pick up a used axle.
 

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Well, I don't think they are switched, the one side fits fine. It has positrac so I'm assuming it's a truck rear end. I spoke with a friend of mine and he referred me to a performance shop close to me that said they could shorten and re-spline the shaft. Thanks for the responses and the suspension chart is just what I needed. If I can figure out which one I have maybe it will be cheaper to just pick up a used axle.
On a 12 bolt I dont think so on the respline, You need to figure out what you have to start with, li8ke how wide and what bolt circle.
 

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Discussion Starter · #8 ·
Ok, here is a pic of the rear end.

From looking on the internet it seems to be a truck rear end. Oh, and I've had the cover off and it does have posi and the c clips are in place. The numbers I have are:

GM55
HC E 07 08 W 1
NF 3896838
F258

I think the F258 means June 25, 1968. I also think the HC number is ratio, Eaton Posi, not sure about the 07 08, made in Warren Michigan. Also not sure about the GM55 and NF numbers.
 

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5 lug or 6 lug? 1970 was the last year for 6 lugs on C-10 trucks, but the 1970 axles were a little longer than 1969 and earlier. Could be all you need is a 69 axle. But if your guy can shorten and re-spline, that's great. I don't think the splined ends are tapered like they are on some 9" Fords, so shortening shouldn't be a problem. But, hey, I've been wrong before!
 

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Its a 8 7/8 half ton rear, 1965 to aprox 1980. It would be cheaper and easier to find the shorter one rather than respline. 68-70 shorter, 71 and up a little longer. should not be hard to find, Pickups, blazers, suburbans, as long as that same cover pattern. fwd had the 6 hole.:tu
 

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Ok, so I'll look for an axle for a 30 spline 68-71 GM 12 Bolt 8 7/8 truck differential. I am out of town this coming week but will pull it out and get to looking. Thanks for all the help!
1971 will be 5-bolt, unless it's from a 4WD truck, like Gary mentioned above. If you go junk yard searching, it would be a good idea to take the correct length axle with you, or at least write down all its dimensions.

And you might as well change the axle bearings and seals. They are available just about anywhere and not too expensive. You will need a tool like this to pull the old bearings. Parts stores like Autozone loan them out.

 

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I had one axle about 1/4" to long on a pro street Nova I built years ago. I put it in my chop saw, cut the 1/4" off, filed the ends of the splines and put it in. Never had an issue.
That's a good suggestion.:tu Seems like splines are usually longer than required.
 

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5 lug or 6 lug? 1970 was the last year for 6 lugs on C-10 trucks, but the 1970 axles were a little longer than 1969 and earlier. Could be all you need is a 69 axle. But if your guy can shorten and re-spline, that's great. I don't think the splined ends are tapered like they are on some 9" Fords, so shortening shouldn't be a problem. But, hey, I've been wrong before!
Well sir you are correct on the difference between 69 and 70 on axles, but did you know that 71-79 four wheel drive 12 bolts use the same axle shafts as a 70 two wheel drive. We put 74 spindles and axles in my brother in laws 70, I then used his primo 6 luggers in my 72 Blazer. It is my recall that 12 bolt axles are tapered.
 
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