Pontiac GTO Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
Hello gentlemen, I have a question, it might sound silly but it is very important for me, and as I always say there is no stupid question,
I have 1968 GTO convertible, I am in the process of restoring the GTO,
it has 10 bolt rear end 28 splin
It is not posi , and I am in process of upgrading the rear end to posi
So how can I find out if it is 8.2 or 8.5
It is all original car,
And if you have any information in regards of rebuild and upgrade kit, out there in the market, I would appreciate the information.

Thanks
Yousef
 

·
Registered
Joined
·
4,219 Posts
Hello Yousef from QATAR,

You should have the 8.2 inch. 10-bolt 8.2-inch B-O-P axle usage:
• 1964-'66 Olds F-85, Cutlass, 4-4-2
• 1964-'72 Tempest/GTO
• 1967-'71 Firebird
• 1964-'71 Buick GS/Gran Sport

It would appear that the 8.5 rear end was used beginning 1971. The diameter of the ring gear is where this measurement is taken and how you can verify it. measures 8.2 inches across the ring gear versus 8.5 inches.

Depending on what you are doing in your rebuild/upgrade will determine what you should do. Are you rebuilding the rear? Changing gears? or? If the rear end is in good shape and you just want to add a posi, PowerTrax is a "locker" type posi unit made by Richmond Gear that does not require you to disassemble the rear end, but you do have to take out the spider gears to insert the PowerTrax posi unit. You can do this yourself if you can do mechanics. Check it out on their website for more information.

If you are doing a complete rebuild such as all new bearings, seals, gears etc., then you probably want to use a factory type of posi unit while you have it all apart.

Be advised. Many of us do not think a posi is a good idea. It is only good for straight line acceleration -drag racing. A posi unit locks up both tires and in wet or slippery conditions or loose gravel can cause the rear end of your car to "kick out" and get sideways or out of control during heavy acceleration - and I would hate to see your nice convertible smashed up. Many with the non-posi rear ends use an add-on air bag to the right rear spring for better traction. I have never done this, but others on this post have and can help you more on this than I. Very easy to install and maybe you want to try this first?
 

·
Registered
Joined
·
4 Posts
Discussion Starter #3
Thank you Jim for the rich information,
What I am planning to do is replacing the brakes from drum to disc and rebuild and upgrade the rear end I want to stick to the original parts though if possible,
I am planning to go for 3.55 and in that case do I have to change the ring and pinion, please let me know if you have any information of where I can get replacement parts.

Thanks
Yousef.
 

·
Registered
Joined
·
4,219 Posts
Yousef,

There are a number of companies that can supply the needed parts. There are different makes for the positraction unit as well, depends on what brand you like.

Seems many of the bearing kits, gears, and even posi units are made by Yukon Gear.

I found a complete package for the B-O-P (Pontiac,Oldsmobile,Buick -all the same) 8.2" rear end. website is Welcome to Ron's Machining Service | Gaines, MI - $675.00 USD plus shipping & this seems to be the best deal to me. Just click on the link.

Eaton and Auburn are 2 good names in positraction units, but $400 -$500 USD just for it. Then you have to buy the gears and all tour bearings, so it can get very expensive when you buy each piece at a time and then ship each item. Buying a complete package can often be your best choice.

Richmond & Motive Gears seem to offer ring & pinion gears sets.

Quick Performance is another website that offers the Yukon brand of parts for the 8.2" rear. Other suppliers also have the parts, but it is all about how much you want to pay for it.

I like Timken brand bearings and National Seals if I am just buying individual parts -both were used on factory produced autos over the years. I am sure other makes will work just as well, but I am not too familiar with some of them, so do not know of their quality.


Hope that helps.
 
1 - 4 of 4 Posts
Top