rear end rebuild 66 lemans - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 07-12-2012, 02:40 AM Thread Starter
 
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rear end rebuild 66 lemans

Second question. With my car body off the frame and soon to be sent to the blaster I'm looking at the ease of taking the rear end off there and getting it checked out. I looks like it hasn't been touched since 1966 and could probably be gone through. But of course rear ends are super expensive to mess with. I also come from the school of thought, "if it ain't broke don't fix it." But I haven't even driven the car so I don't even know if it has problems or not. If you all were in my shoes what would you do? Have a rear end shop look at it? Or put a completely different rear end under the car? It's a 66 lemans convertible with a 3.23 so I assume it's a 10 bolt? Did these do alright in the cars for everyday type stuff? Posi would be nice but I'm probably getting greedy there. Unless of course it was an easy swap.
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post #2 of 9 (permalink) Old 07-12-2012, 08:43 AM
 
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I've "almost" rebuilt mine top to bottom. Diff will not be touched until there's a problem.

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1966 Pontiac Lemans Convertible
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post #3 of 9 (permalink) Old 07-12-2012, 09:27 AM
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These differentials go for decades if not abused. In a '66 Lemans, I'd wager it's just fine. The only reason I pulled the 3.36 diff out of my '67 GTO at 240,000 miles was because a friend gave me a 2.56 diff and I wanted better fuel economy...there is nothing wrong with the original unit. I've owned and worked on many of these cars, and know that you leave them alone until they break..which is almost never on a street driven 326 powered car. The overhauled and tweaked with units are the ones that tend to fail, due to incorrect re-assembly by well -meaning but misguided non-experts. The only real issue with these rear ends in normal driving is the wheel bearings getting sloppy and wearing the axle shaft out. Replacements are available and affordable, new or sometimes used. Final word: leave it alone, or change the gear oil and leave it alone after that!!!
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post #4 of 9 (permalink) Old 07-12-2012, 01:57 PM Thread Starter
 
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Copy that, good advice and I will take it, thank you. Probably repack the bearings and call it good.
post #5 of 9 (permalink) Old 07-12-2012, 06:40 PM
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Bearings are not repackable/serviceable. They are sealed units. If in doubt, have new ones pressed on to the axles and you'll be good to go.
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post #6 of 9 (permalink) Old 07-12-2012, 11:03 PM
 
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I would at least check the bearings on the axle shafts. I pulled both mine and both were worn completely worn and wobbled out, had to pick up 2 new ones from rock auto.

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post #7 of 9 (permalink) Old 07-13-2012, 09:32 AM
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With most of the above. A lot depends on how you're building the rest of the car and how you're going to drive it. A 10-bolt in good condition can live forever behind a more or less stock engine that's only occasionally driven "with gusto" on street tires, even if it's a 400 or 455. Push torque up over 500 or better and install a set of sticky drag radials then use both "as intended" and it will probably surrender sooner rather than later.

A limited -slip ("posi") is nice for launch traction...

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post #8 of 9 (permalink) Old 07-19-2012, 01:53 PM Thread Starter
 
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So I took the rear end cover off today and it was pretty well destroyed inside. I won't get into details but there were lots of chucks of metal. Probably part of the reason I got the car pretty cheap. Anyway the housing is still good now I'm wondering what my best course of action might be. Should I get the 10 bolt rebuild and call it good? Or get creative and do something else. I really like the 3.23 gears it has in it but the rear drum dust covers are pretty rusty and ideally I'd like posi. Here's options I've though of:

1) rebuild the 10 bolt keep it as is
2) Put a 8.5" ring and pinion on the 10 bolt
3) Swap in a 12 bolt preferably with a limited slip
4) I've heard some doing a ford 9", ford 8.8", or maybe one I haven't thought of? I will probably end up doing disc brakes in the front so swapping in disc brakes might be a good in the back to if I'm already swapping rear ends. Any good fairly straight forward swaps out there people know of off hand? Ideally something the same width, limited slip, 3.23 gears, and disc brakes. Probably asking for too much.
post #9 of 9 (permalink) Old 07-19-2012, 08:36 PM
 
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eou,

I opened up the rear end of my Tempest with the expectation of a quick look and refill with gear oil and found metal chunks in the bottom. I took it to a shop and they rebuilt it for around $500. It is a 3.23 posi and they only had to replace bearings and seals the posi unit, carrier and ring and pinion were fine. I also had them weld the axle tubes to the cast center casing. I have seen the plug weld that holds the pressed in tube from turning break-off cause much more damage and rendering the rear end completely useless...

Here's my $0.02 on your 4 options:

1) rebuild the 10 bolt keep it as is
Probably a solid plan, and other than whatever is broken, won;t cost too much..
2) Put a 8.5" ring and pinion on the 10 bolt
I'm not familiar with this one.
3) Swap in a 12 bolt preferably with a limited slip
Junkyards may have a rear but the mounting will have to be the same and then you may also need a rebuild on this one as well
4) I've heard some doing a ford 9", ford 8.8", or maybe one I haven't thought of? I will probably end up doing disc brakes in the front so swapping in disc brakes might be a good in the back to if I'm already swapping rear ends. Any good fairly straight forward swaps out there people know of off hand? Ideally something the same width, limited slip, 3.23 gears, and disc brakes. Probably asking for too much.
MOSER Engineering makes complete rear end assemblies (Ford 9" or 12 bolt) with disc or drum brakes, and a variety of gear ratios. This will be an expensive way to go with Moser's website having lists around $3K...
-Thor
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Projects, Barn Finds & Restoration Discussions

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