# 72 LeMans 10 Bolt rear end questions



## HelpDeskGuy (Sep 4, 2008)

Hey everyone. I have a 1972 LeMans I am playing with. I picked up a 455 in trade and slowly but surely I am rebuilding it. In the meantime I have a 425HP 454 I am shoving in so I can drive it around this summer. I am just a couple body parts short of the complete endura front end and will be hitting some swap meets to try and trade for the parts I need. Anyway... It has a 10 bolt rearend and I have found a posi unit with 3:73 gears that the guy says is for a 10 bolt 8.5? Is this what I have in my car? Is there a way to tell? Oh and by the way if anyone reading this lives near me (Indiana) and has the body parts I am missing I will trade a laptop for them. Just ask. PM Me.

If anyone has ever put a BBC in a 71-72 LeMans or GTO and has any "I tried to do X and it didn't work" hints for me I would really appreciate it.

Thanks in advance.

To date I only have $625.00 in everything I have for the car. That includes motors (455 and two 454's), Endura Front End Parts and the car itself. Yeah I am pretty proud of that!


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## Petey D (Feb 14, 2009)

Stock rear in Pontiacs was 10 bolt 8.2in. You can tell if it's a Pontiac rear just by looking at it. The dif pot will look kind of like it has ears.

I have no exp personally, with bbc's in a Lemans, but a guy I bought a bunch of parts from had a 454 in a 71, with a th400, a stall converter, and the stock rear. It ran like a champ, from what I hear it did 9s in the quarter.

Hope that helps a bit, and welcome to the site.


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## Too Many Projects (Nov 15, 2008)

To put the Chevrolet motor in, you will need the Chevrolet transmission too and exhaust manifolds and frame towers and ALL the brackets to hang the alternator and power steering pump and you'll have to get the fuel from the left frame rail all the way over to the right side for the Chevrolet fuel pump, you may need to put a Chevelle radiator in it to get the hoses to line up, the starter and wiring is on the opposite side and on and on and on. I, personally, wouldn't look at this as "throwing it in" temporarily because it's a LOT of stuff to change twice. By the time you've spent all the coin for the changeover, you probably could've just finished the 455 and bolted it in.....


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## geeteeohguy (Feb 2, 2008)

TMP is right on. Plus, the speedo cable is on the opposite side, the engine mounts are different, and a 454 BBC is a downgrade from a 455 Pontiac, in my experience. The last encounter I had was with a 454 in a '68 Firebird....I raced him with my worn-out '67 ragtop with 173000 miles on its original 400, and smoked him. My advice is to slow down, get all the parts you need (on the cheap!!) , and have fun building the 455. Then you won't be having to re-do a LOT of work, and besides, it's waaay cooler to have a 455 powered LeMans than having to say "yeah, well it's got a 454 in it for NOW, but I'm GONNA put in a 455....." Of course, I am totally biased on this, and you are entightled to do as you see fit. Good luck to you, and we're here to help if we can.


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## HelpDeskGuy (Sep 4, 2008)

*Update*

Hmmm...8.2, I guess i will have to try to get any numbers off of it as two other guys told me that it was an 8.5. :rofl:

The 454 I have has all the components already on it (alt ect...). I am going to run an electric fuel pump so that problem is taken care of. They put batteries in the trunks of newer cars so running a little longer cable won't be an issue I don't think. As far as building the 455 for what I would have in the change over...man I really don't think i could finish it for 1/8th of what the change over will cost. I have been doing my homework and dollar for dollar a BBC is much cheaper to get the same HP and Torque out of. Heck for that matter a SBC Stroker is the cheapest way to go for the most bang for your buck. But I am a Big Block Guy. Around here a set of Pontiac pre-70 big valve super flow heads that have had the bowl work done and are ready to rock have been going for around 2K and up. I have less than that in the whole 454 and it is turning out 450HP+/600ft Torque. Remember this is what it is...and it is NOT a GTO. There will be no GTO emblems on it. I personally don't believe in doing that. It will have an endura front end...It will look cool...but in the end it is just a toy. 

I picked up a 1970 GTO last week w/no motor or transmission. They guy had ripped all the interior out and put in aluminum for racing. It is the real deal. It will not get a Chevy motor...I think i am going to put the 455 in it. Another project. hahaha...Just what I need. 

I actually have acquired a Muncie M-20 fresh rebuilt I think I am going to put in the Lemans so i don't think i will have to worry about the 400 Turbo.

Bummer on the rearend tho...

As always I appreciate you guys. :cheers


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## 05GTO (Oct 6, 2004)

HelpDeskGuy said:


> Anyway... It has a 10 bolt rearend and I have found a posi unit with 3:73 gears that the guy says is for a 10 bolt 8.5? Is this what I have in my car? Is there a way to tell?


Here is a link that may help with ID'ing the diff, Good luck and welcome to the forum, 8.5 was available on Pontiac's after 70.

OLDSmobility.com - The 1967 Oldsmobile Cutlass and 442 Resource - GM 10-bolt Differential Technical Information


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