Ok, pulled my thread from earlier. All this time I thought all SS cars were posi. I went so far as to pull my build sheet today to prove it. Well, I've only been mistaken once before...and I divorced her. Turns out I've got a 2.73 peg leg. I want to swap it for a 3.73 posi. Can I do this and maitain the original chunk housing and axles? What's involved? All help appreciated. BTW, will I notice a marked improvement in performance or is this a waste of money for the return?
Thanks!!
Stacey

Yes you can swap it and use the same axles and IMHO you will definitely notice a performance improvement. If your motor has decent power, you'll burn rubber till the cows come home with the deeper gear.

A little confused. I read a couple posts in the forums that said you can't convert a peg-leg to posi without changing axles...? Do I have that right? I would like to keep original parts and hide the performance.

The axles are the same, no need to swap. What you need is a new Eaton posi, 3.73 gears and a good installation kit. Everything will fit into the housing that you have now.

BGH,
How industrious an effort to do it on my own? Bear in mind, never done one before. Someone else mentioned I should balance the drive shaft while I'm at it. What's the point?
Stacey

You will need to know how to set the pinion depth, bearing preload and backlash to get the correct contact pattern. You will also need to know how to read the contact pattern so that you will know what adjustments need to be made to the pinion depth. There are a few special tools that you will need, like a dial indicator with a magnetic base, a press with a bearing seperator and a few others.

Stacey,just a thought,going from 273 to 373 gear is a huge jump,do you really want to turn 3k+ rpms & 60mph,waste tons of fuel,and generate a lot more motor heat & noise,then go with 373 gear.

Whats you current motor/trany setup?

Is your current motor/cam setup to run well with 273 gear,if yes it will not be good with 373s unless you run a lot more cam etc. The motor/car will run out of cam/rpm so quick with 373s if it's macthed for your current 273 gear.

Now if your planning on a lot of perf mods and running it at the track then going from 273 to 373 makes some sence,but if your motor is stock to very mild for 273's then going to 373 is too much for a crusier with no engine mods to take advantage of the 373's.(IMHO) I would opt for 3:31 to 3:42 max for a stock to mild perf motor setup cruiser with an occassional trip to the strip. This is because the 331s or 342s will not waste as much fuel and will also generate less motor noise & heat than the 373s. But ,the 331 or 342 gears will still be a big imp in perf over the 273s,trust me you will like perf gain either of those gear sets will give you.

Try to see if anybody in t/C lives near you that is currently tunning 373s and take it on the open road 2 60-65 mph to see if you like it before committing to the change. For example,i have gotten 4 people to do that in the past couple yrs and 3 of 4 people that thought they wanted/needed 373's said they were happy they took my advice to test ride the 373's and DID NOT CHANGE TO THE 373'S after the test rides for all the reasons i stated above,they opted for 331 & 342.

Latsly,what ever gear you change to will spin your driveshaft a lot more so i would definately have the universal replaced if they are oldalong with having it ballanced or you will very likely end up with some drivline vibration.

Scott

I agree that the gears not quite as tall as the 373's would give you a much better cruiser. I am about in the same boat as you with the one legged 12 bolt, but I already have the 373's. I am not going to the track, and don't really care about doing burnouts, so I am going to stick with what I have.

The 3.42 is very popular for street driving. It will be a very noticable difference from what you have now, but will be easier to live with on the highway.

IMO, a 3.55 is a great compromise gear ratio if you want crisp acceleration and would like to be able to cruise hwy speeds without running really high rpm's. i stuck with the original 3.31 ratio in my '68. if you have some torque, you can have great off the line performance with the lower ratios such as a 3:31, 3.42, 3.55.

3;55s are not very street friendly unless your caomparing them to 410,390,etc and 355's turn plenty of rpm at highway speed like in the 2900-3k range depeding on tire height. If your running a bbc you have the trq and dont need them unless your doing alot of racing or have a high strung small motor like a 69 dz 302. So stay with 331sor 342s max and you will be much happier.

Scott

Guys,
Great input. Should update my sig. I'm running a 402, stock heads, big cam, TH400, 2500 stall. Really could use a little bigger stall but won't help around town. I always thought I had a posi with a bigger gear (I really did read the build sheet) any rate this explains why the low end is not what I think it ought to be. Am I racing, no. Just want more torque. About to have the heads worked. Runs rich, think I've got some seapage (sp). Can't dial it out. The big cam doesn't help. I figure with the cleaned up heads and the lowered gear I will find the satisfaction I deserve ...LOL. I drive it so I truly need a good compromise. Maybe 3.42's are best...?

WITH A 402 I WOULD GO WITH THE 331's,it has some trq.

My friend had a 292 comp cam in a 402 with 244 deg dur @ .05,.550 lift, with 110 L/S angle single patt cam and it did fine with 331s,what are your cam specs and general motor setup?

Scott