My f85 has a 10 bolt with 2.73 gears. I have been kinda looking for a gear set for a while now and kinda looking for a hole rear end to swap maybe...


I found a 10 bolt out of a 1969 lemans with 3.90's of course the guy selling it to me said it will swap right in... But im sure he would tell me anything for me to buy it.. lol.


So I ask of y'all will it ? directly fit with no modifications ?

 

It will require different rear springs and a different driveshaft. It's also a couple of inches wider. Other than that, yeah, it's a "bolt-in"...

 

Will the drive shaft need shortened ? Or to be longer ?

 

Shorter i think.

 

Hello:
I did the same thing to my 66 F85 years ago, the rear was out of a 70 Chevelle 12 bolt w/4-10 posi unit. I don't remember any big problems, just normal stuff we all put up with doing this kind of thing, as far as width, the rear shoes were L60-15 mounted on 8" deep Chevy Rally Wheels and they still tucked under the wheel wells easily. We are blessed w/ huge wheel wells on our 66-67 Cutlass' though, my friends were all jealous of that, their Novas, GTO's and Chevelles all had small wells, I had M50-15's on the rear at one time as well.
Thanks, Ron

 

thanks for you help everybody !!!

 

A 2.73 is a nice highway gear. My Chevy has a 350/350 2.73 posi setup, and was ordered that way by my granddad, and it hauls up off the line respectably and will cruise along all day at 70 mph and 2500rpm with 225/70/15 tires. However, a Monte Carlo which was not an SS with a small block 350 is not, in my opinion, a muscle car; it's an old car with era-appropriate *****.

Now my 442, which runs like crap, has 3.08 posi, and that's something like 2800 at 70, I estimate, with the same tires. However, more cam and 50 more cubes on a lighter car may make it perform in what people would consider muscle-car-ish. Reason I am mentioning this is you are in Tampa, and FL is a big state. I grew up in Orlando, and I live in lower Indiana now, and both places require interstate driving for decent amounts of time. Make sure you choose your rear end correctly, because, if you stay with a non overdrive transmission, steep gears will tax that engine hard when you go visit someone at highway speeds. I personally don't think one should run over 3k rpm for cruising speeds.

 

You can cruise @ 3000 RPM all day long with EASE. The only thing that this is hurting is the wallet for the extra fuel. So many guys are spoiled by modern cars with OD transmissions. I used to tow my race car for hours on end @ 3300 rpm with the 455 / T400 & 3.73 gear set in my old truck. Did it for years with ZERO issues.

 

Thank you again everybody for your responses.. I have no desire at all to drive this car on the interstate....maybe some back streets... (its plated..) As it sits its a gutted, 3000 stall, open header, big block, n2o monster as of right now..... maybe later in life ill switch things up but for now it is what it is... :-)

 

The 69 rear is probably a P type 10 bolt, and should be a bit under an inch wider overall than your original rear. Pontiac used the same bigger u-joints as Olds, and the driveshaft should work fine. While the 66 used plates and bolts to secure the bottoms of the rear springs, the later rear with cup retainers will work.

 

Why would the 69 Pontiac rear end be wider? 1964-65 Olds A bodies are narrower by 1" than the 66-72 Olds A bodies. The 69 P type 10 bolt should be exactly the same width as the original 10 bolt in his 66. The driveshaft length may be slightly different.

 

Is the '65 carrier the same as a '69 if they are both 10 bolt?

 

I live in the Tampa area (Brandon to be exact) and build rear ends. If you need any tips or advice, feel free to contact me and I'll do my best to help you out. Not a sales pitch, just an offer to make sure you're headed in the right direction. You can pm me or call 501-454-4947 and ask for Bruce.