Technical Chevy three speed trans swap

Have a 63 Bel Air stick six car. It only has 29,000 on it and I want to upgrade the trans to a 70 Saginaw box keeping the column shift as to keep the stock look and make the driving a little more pleasant.. Has any one out there done this upgrade and if so what did it take to do it. I already am aware of the drive shaft needing to be shortened and I think the bell housing has to be changed but what else do I need to know.

 

I do not think the bellhousing will have to be changed,just the driveshaft modified and maybe some linkage tweeking.

 

Bellhousing is not a problem.That all synchro saginaw is a good,stout trans.Definitely will require some linkage fiddling.

 

You'll need to swap slip yokes, the early trans is a course spline, the later Saginaws, a fine spline. Linkage will have to be lengthened, shortened, bent differently, and will require different trans shift levers. Maybe you can get real lucky and find the later Saginaw 3 speed with overdrive. I am Butch/56sedandelivery.

 

It's been 35 years ago, but if I remember, I had to turn down the outside diameter of the front bearing retainer to fit the hole in the earlier bell housing.

 

Well, I'm into it now and there are a few things I am sure of now. First thing is the drive shaft will need to be shortened 5" and the yolk needs to be changed to a fine spline yolk. Next I decided to change the bell housing as the hole for the bearing retainer on the old trans measures 4 1/8" while the Saginaw measures 4 5/8". Just easier to make the swap. As for the linkage...............I'm not there yet so guess I'll see what needs to be done when I get there.
So much for an easy " all ya need to do is just change the tranny" !!! hahaha

 

You may have a truck transmission. the bearing retainer is larger on the truck, but a car retainer will fit. An early car transmission bell housing and clutch,will fit the later transmission. Truck transmission will have a lower 1st gear and may not be great depending on your diff ratio.

 

Trans going in is out of a 1970 Nova.

 

Years ago we (Dad and I) put a 4-spd saginaw in a '55 1st series Chevy truck, with a 235. We had the same problem. The nose cone OD was too big on the saginaw. It's been a long time, but I think we put the nose cone from the stock 3 speed onto the saginaw, (or maybe the nose cone was from a different transmission, like a 4 spd granny from early '50s, been 30 years now) but I remember vividly the bolt pattern and bearing race was the same size, only the OD that fits into the bell housing was different. In other words, it was a simple bolt in swap to make the Saginaw fit the early bell housing.

So...I'd take a look and see if the 3-spd snout will bolt to the 4 spd, if not then maybe someone knows which nose cone will bolt to the Saginaw and fit in the early bellhousing?

matter of fact I still have that Saginaw packed away somewhere, it came out of a '69 Camaro when my buddy went for a Turbo 350 with a shift kit.

Kipp

 

I appreciate your thoughts but I already have the bell off and I have the replacement ready to go. All I need is time to get back at it. Life has a funny way of changing your plans. Should be back at it by early next week though.

 

I have had one of those transmissions in my 48 behind a 250 for years and you will really like it when it's all said and done. I used a floor shift but I don't think you will have all that much hassles fitting the column shift linkage to it.

 

Hey...Thanks for the positive words. This whole thing started with replacing control arm bushings and shocks all around and it snowballed to upgrading the master cylinder and on to upgrading the trans. In the end it should be a more pleasurable drive.

 

In my estimation the benefit of the transmission swap is not worth the effort. If you were talking about replacing the six with a V8 thats what I would do.

Gary

 

i'm suprised you are going thru all this effort to replace a perfectly functioning trans. i can understand replacing it if the original transmission was busted or to install an overdrive tranny. back in the day I did perfectly fine with the non-Synchro first for years. first my fiat and mg and chevys and fords. and my 23 buick and 26 dodge. learning the method to be able to downshift into first while you still rolling... shit... i still do it all the time at work with the big trucks. (and i still grind gears sometimes.)

 

Is there a problem with the existing, stock transmission ??

 

Yeah..... I don't like it.

 

A V8 ????? Then I would be like everyone else. I dig the look of the six. I put the Wee 8 in my 32 .
open

 

Just was asking why.

 

That's cool.......but I really didn't like it. Felt going to the fully syncro box would be a good upgrade.

 

You can down shift into first with those trans but you can not use the clutch.

 

OK. If anybody wants to do this upgrade I can tell you for sure you will have to be prepared to have the drive shaft shortened, about 5" in my case. You will need a fine splined yolk for the driveshaft. You will have to change the bell housing to a 403 bell and you will probably need a longer speedo cable, at least I did. Altering the linkage was fairly simple, some adjustment and some fabrication but nothing to crazy.
The bell housing change is because up to and including 63 GM used there own Borg-Warner transmissions having a 4 1/8" bearing retainer. The bell housing was a 421. After 63 they farmed out the trannys to Saginaw and Muncie which has a 4 5/8" bearing retainer.
The 421 and the 403 are the last three numbers in the casting number. They look identical except for the retainer hole.
Just for the record, I am really happy with the outcome. Yes, I feel it was worth the effort and I learned a little more about Hot Rodding along the way.