Rear End Housing Recommendation - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 11-27-2017, 12:14 PM Thread Starter
 
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Rear End Housing Recommendation

Based on advice from this forum, I am planning to not build up a '65 stock, rear end assembly into a 3.08 posi. It sounds like that will not be robust enough for my recently built stroked 389. My engine builder estimates the torque will be in the low 500s.

So I have two housing options available to me. I have a '67 nodular 4.33 10 bolt that I can change over to a 3.08 - this came out of my '67 car because I didn't like the 4.33 gears and I had a 3.55 spare (also nodular) to use. Or I have a 72 A body 10 bolt that I can upgrade to a posi and put in 3.08 gears.

My question is, from a strength standpoint will the nodular '67 8.2" be equivalent to the '72 8.5" rear end? Or is one of them a better choice for strength and longevity? Changing over the '67 will be cheaper and easier because it already has good brakes and bearings on it.

This is not a race car but may have an occasional aggressive launch here and there. It will have a Coan TH350 and possibly 2500 stall.

Thanks for any input.
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post #2 of 4 (permalink) Old 11-27-2017, 04:21 PM
 
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The 8.5 A-body housing has considerably more pinion support than the Pontiac nodular 8.2, while also having tapered axle bearing axles which are the best for long term life as well as cornering forces. If the '67 nodular 8.2 rear is not original to your '67, & your '67 was not factory equipped with a '67 4.33 coded rear, I'd probably shelve it, have it checked out, clean it up, then offer it up for sale to the collector that's searching for that date range nodular rear for his '67 RA or '67 optional ratio 400 HO car. Not original to your '67, getting it into the right hands would ESP be the case, if the housing is very clean, rust pock & pit free.

On the other hand, if the '67 nodular hsg has suffered the ravages of Midwest or East coast winters, lot of pock marks, rust pitting, it will take a lot of proper body work to make it presentable, & will never be a top shelf piece. In that case, if not concerned about the limitations of less pinion support & of crappy sealed axle bearing axles, you could have the nodular 8.2 built with a mid ratio Auburn posi carrier & a good used set of 3.08's. Sell off the 4.33's & the 4 pinion low ratio carrier in separate deals. Over the last 5 years, I've sold off three sets of relatively low mile original dated 4.33 gear sets. Had to slow down taking in differential work with all the other work with new home base & getting the new shop up. also have not been making club conventions, MCCAN, etc, & as a result, have not been getting connected with hardcore collectors that are actively working on 4.33 geared '69 & 70 models.

Which '71-72 8.5 A-body housing do up you have, the most common one with the squared off lug sat bottom, or the much less common style that takes a round cover?
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post #3 of 4 (permalink) Old 11-27-2017, 09:38 PM Thread Starter
 
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Pinion Head, thanks for the reply.

The '67 4.33 nodular rear end is original to my '67. So even though I probably will never use that ratio again, I will hold on to those parts as long as I own that car. Also, the midwest has indeed taken its toll on the outside surfaces with some light pitting. So selling for highly collectible price is probably not in the cards.

Since I don't plan to sell either car anytime soon, it would not bother me to use the original rear end of one car in the other. But since there is not a significant amount of cost difference, it sounds like the cleanest approach with what appears to be the best result for a strong rear end (based on what you said) will be to build up the 8.5.

The 8.5 housing has the squared off lugs, and the cover is scalloped on the sides.

Two follow-up questions just out of curiosity:
1) Why did you suggest a used 3.08 gear set for rebuilding the nodular rear end? Just cost savings?
2) My 4.33 axles seem to be larger diameter than one of my Lemans axles. Does that mean they are the HD axles?

Thanks.
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post #4 of 4 (permalink) Old 11-28-2017, 03:19 PM
 
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my suggestion for used ring & pinion, that was only if you were going 3.08's with the early Pontiac 8.2 10 bolt differential. There are no new 3.08 gears for that particular application, have to source nice used. On the axles, the HD Safe-T-Track Pontiac rears had the hot forged axles, they will have a rough finish down the length of the axle. The std duty Pontiac 8.2 axles will have more of a machined surface.
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