1965 gto convertible

[Z ROADSTER]

I have a question for all you old goat experts . Friend of mine just bought a 65 GTO Vert. 4-speed 389 4-barrel carb. No AC or pwr brakes but it does have pwr steering. It has a 10-bolt rear end & I thought it should have come with a 12-bolt . Can someone clear this up for us ? Also what gear ratio should it have if it is completly stock ?
Thanks

[my first gto]

I have a question for all you old goat experts . Friend of mine just bought a 65 GTO Vert. 4-speed 389 4-barrel carb. No AC or pwr brakes but it does have pwr steering. It has a 10-bolt rear end & I thought it should have come with a 12-bolt . Can someone clear this up for us ? Also what gear ratio should it have if it is completly stock ?
Thanks

Thats the RIGHT rear for it, in 1970 you could get a 12 bolt but not any sooner .....frank

[Z ROADSTER]

You gotta be kidding !
I bought a 1967 Chevelle SS 396/350HP 4-speed brand new right outta the Army and it came with a 12-bolt .

[my first gto]

You gotta be kidding !
I bought a 1967 Chevelle SS 396/350HP 4-speed brand new right outta the Army and it came with a 12-bolt .

Chevelle is a Chevy, Not a PONTIAC Chevy had them in 1964 Not Pontiac only after 1970 could you get a 12 bolt...Frank

[Firebirdjones]

You got the pontiac 10 bolt with bolt in axle shafts and an 8.2 inch ring gear. Not the strongest of rears but it's what pontiac used right up through 69, even in the heavy hitting ram air IV cars.

I would venture to say since the car doesn't have factory A/C and it's a 4speed then the standard rear gear offered would be the 3.23,,,,with 3.55 and 3.90 being an optional gear if so equipped.

Send the vin to Pontiac Historical Services and they will send back an original window sticker and paperwork. It will tell you exactly how the car came equipped.

[Firebirdjones]

You gotta be kidding !
I bought a 1967 Chevelle SS 396/350HP 4-speed brand new right outta the Army and it came with a 12-bolt .

All the chevelles that were SS's from 66-72 have 12 bolts. You could get them in 64-65 if you ponied up for the 300 hp version of the 327 and in 65 they stuck a few 396's in as well,,,which also got the 12 bolts.

Pontiac firebirds were much the same way,,,67-69 got pontiac 10 bolts,,,,but in 1970 only the T/A and Formula got the chevrolet 12 bolts and it was a one year only rearend. I have a 70 formula and it's one of the easy ways to spot a fake.

Now the chevy camaro's on the other hand from 67-70 got the 12 bolt in all the Z28's,,,and in any SS that at least came with the 350/300 hp engine (or 295 hp depending on the year) or any combination of 396's offered.

[Z ROADSTER]

Thanks ! My friend does have the "POS" on his vehicle . My 67 SS had an A.C. with what I assumed was the wide ratio Muncie and I know a 3.08 gear which I later changed to a 3.73 with 9" whitewall slicks . Ran 13.80"s with the red line 2 ply wide ovals taking off in second gear when it was brand new in pure stock class " A Stock " .

[Firebirdjones]

Thanks ! My friend does have the "POS" on his vehicle . My 67 SS had an A.C. with what I assumed was the wide ratio Muncie and I know a 3.08 gear which I later changed to a 3.73 with 9" whitewall slicks . Ran 13.80"s with the red line 2 ply wide ovals taking off in second gear when it was brand new in pure stock class " A Stock " .

If the car came factory with those 3.08's then it had the wide ratio muncie (M-20),,,,,,easier on the clutch that way. Usually GM would only allow the optional M-21 close ratio if a tighter rear gear was ordered in the range of 3.55-3.73 or so.
Sounds like your car runs good though.... I run my 70 formula in pure stock as well on the stock bias plys,,and 3.31 gears in the 12 bolt, automatic 400 ram air III and it runs 13.60's at 102 mph. Not too shabby for an ole stock poncho motor