I know this is probably a stupid question for most, but please bear with me, I am trying to learn.

I have a '68 that I am slowly working on. I assume the factory sent these cars out with 8.2 axles. Correct? What are the carrier/ gear ratio cutoffs? Meaning, if you had 3.73s, what else would go on that carrier.

I have not pulled the cover to confirm the ratio. I assume it's pretty high. I was guessing around 2.73 or so, but I don't know if that's even an available ratio.

Now the fun stuff. What TQ/ HP would these rear ends be okay with? I am not building a drag car. But I expect to be around 350HP or so. Also, what limited slips, ect are recommended and what gear ratios should I really be looking at?

The car is gonna be a cruiser that will see hiway time. So, I want to keep freeway speed rpms down to an acceptable level. Te TH400 and the very mild 455 will take care of getting it moving. Again, not a wild car. Strong runner, but on cheapo unleaded.

Thanks!!

Dave

Dave, if it has the higher gear set, you will probably need to order a gear that is thicker than the lower gear sets. The actual width is different. This will take up the space difference. Not uncommon, and readily available. Where are you at in Washington? If you're near the Seattle area, call Randy's Ring and Pinion. He'll have all the knowledge, and parts you'll need at a good price. My buddy had him redo an 87 Vette rearend that is going in a 62 Vette. I'm sure some of the other guys on the site can give you exact numbers and specs.

My 2 cents worth:

My 3:55 runs about 3000-3200 rpm at 70 mph. TH400. Auburn Pro-Posi. 450+ HP. 500+ lbs Torque.

If its the original rear end, there should be a 2 letter designation stamped on rear side of the driver's side tube. This will tell you what the original rear gear was. Take a peak there.

If you do the work yourself, be sure to get an installation kit. This includes bearings, shims, etc. Also, when you order your parts, make sure your sales rep understands that you have a "BOP 8.2" rear end. Sounds simple enough, but... You're looking at about $700 worth of parts, including the posi unit.

as bronze said. look at the 2 letter code on the rear driver side of the axle. it will be about 1" to the left of the brake clipt. use a wire brush to clean off the rust so you can see what the stock ratio was!

Thanks guys!

Looks like the stamp on the axle is XB. Does that make any sense?

Dave

I did some digging. Looks like it has 2.56 open rear end.

I want to keep this car as a hiway cruiser. So, I don't wanna dive to too low a set of gears.

Dave

should have the 2:56 as you discovered. wil have the numbers 41:16 on the side of the ring gear if this is the stock gear ration!

I found an XB axle underneath my '67, despite my PHS documents that said it left the factory with a 3.08 rear (standard for an auto 400 model). I figure some previous owner desided he would rather have a freeway cruiser.

That axle is now sitting on the side of the garage. I decided the HD 4 pinion posi 3.55 I found in a junkyard was better.

So, the question is, what is a good compromise ratio for my needs? I need to have the ability to do some freeway cruising as well as have some fun on the street.

Since I could concievably drive 100 miles or more on the freeway, I want to keep things civil. I also want to be able to have a little fun with some of the newer cars on the street.

I know a low gear and an OD trans would be the hot ticket, but that's just not in the cards today. Perhaps an OD unit later, but that'll be a while.

I am thinking between a 3.08 and 3.23 gear. Posi of course. I was thinking a 3.55 gear would be a touch too low.

And suggestions?

Dave

Dave,

my convertible has a 3.23. With the 400 4 spd it's a very acceptable gear for both acceleration and top end. My cammer has a 3.55. With the 4.1 1bbl OHC the gear is nice to get the car up to speed. But it tops out quicker and adds a few more revs. But it's not excessive. It's another very street-able ratio. I guess it all depends on how much gas you want to burn getting between points A to B.

i would say a good compromise would be 3:23 to 1. it will give you a better performance stance while still maintaining your mileage for cruising the freeway! if your not concerned with mileage id say gear the hell out of it and watch those new cars become blurrs. till you run out of gear and motor. lol make a light to light car!