Looking for rear end advice

[ARTMAN]

It has been a year since I completed my 300/st300 to 401/st400 swap in my 1966 Skylark convertible, It is a kick *** engine, and tranny. It was worth the effort. I find myself in need of gears, My current set up is the original 10bolt, posi, 278 gears. It gives a serious launch, maybe due to the St400 tranny , but where I lack is when I am going 20-30mph and hit it, I got nothing. Any advice to where to buy 355, or, 373 gears, and a new posi unit, and axles, I spent tooo much $$ last year> I would rather keep my casing if they fit? will they?

[suntreemcanic]

Don't know anything about availability of gears for your differential. I am happy to hear about the launch, I am putting a ST400 / 425 in my car.

[Bob]

when I am going 20-30mph and hit it, I got nothing

So you are happy with your launch and then the car is a slug from there on? (gears)

Or maybe you are cruising and punch it and "have nothing"? Like the car is not downshifting?

[BigRivy]

Is your switch pitch converter switching to high stall at full throttle? "Got nothing" isn't the most descriptive term. What are you expecting and what do you want it to do? Is your engine sorted and tuned?
To answer your original question about gears you need to identify exactly what rearend you have and call the people who make this stuff and ask them what's available. Some good companies to look up are-
Mark Williams enterprises
Strange Engineering
Moser Axles
Randy's Ring and Pinion
and about a dozen others that a simple internet search will turn up.
You should have no problem with being able to use your stock housing if the parts you want are still available. Doing a rearend right that will take a lot of abuse will not be real cheap. An Axle kit with gears and a new posi unit with labor to install could easily top $2000. Racing type swap meets are a good place to find used parts. Look up some local drag racers, a lot of those guys have buddies that have a lot of stuff they may not be using. Although most of it will be 12 bolt stuff. You may be able to find a deal on a whole used assembly that's already set up. I've seen all kinds of stuff like that at swap meets in years past.

[telriv]

If things were CORRECT it should just about fry the tires. At 20MPH it should downshift to 1st. gear automatically. Somethings WRONG.

[mottrodder]

Artman, I agree with Telriv. If you posted more info, maybe some transmission or tuner type people could offer some suggestions. Are you confident that your trans linkage is complete and functional ? I think I sold you some exhaust manifolds and motor plates. (lost your email address). Would like to know how things are going. All is well here. Mike

[39CENT]

If you install a ford 9 inch you can put any kinda gears you want. pretty easy to swap just the differential pumpkin.

[ARTMAN]

OK, Let me try to clarify, Getting a great launch, Switch pitch seems to be working , not exactly sure how to test but, I have no issues off the line, Need more pull , Gears right? when I am driving 20MPH, and hit the gas, It do not think it is down shifting properly, 4 bbl seems to kick in, but no pull. I have a rebuilt carter AFB, Done by Russell Martin, I had a vaccum leaked when I first installed but that has been fixed and tuned.
I have no throtle hesitation what so ever.
How do I check to see if switch pitch is working? I found used rears on Ebay anybody heard of JD race and restoration, They are selling 10 bolt 3.36 posi for 1500.00, I thought I could replace my guts for cheaper. Mottrodder, good to hear all is well.

[wkillgs]

anybody heard of JD race and restoration, They are selling 10 bolt 3.36 posi for 1500.00, I thought I could replace my guts for cheaper.

That would be Jim, aka 'Monzaz' on the boards. Good guy, knows the Buick rears very well.
Check out his website at www.jdrace.com
Yes, he can hook you up with a carrier, gears and install kit for your 8.2 rear.

At what rpm are you having issues?
I wouldn't blame the gears just yet....
I'd suggest putting an advance curve kit into your distributor to get all the timing (30-32 degrees) in by 2700-3000 rpm or so. It'll make a huge difference in how the car pulls in the lower rpms.

The high-stall converter also does most of it's work between launch and 3000 rpm.

[ARTMAN]

Well, My cousin Billy told me to look for a swtich on side of throttle,black button, when you floor it, the back of the linkage will hit this button and down shift, Sure enough, I guess it would have been a clip, is missing on my car. nothing is hitting, Not sure how I can fix, start searching ebay.