[mt94ss]

Anyone have any tips on rebuilding a mid '70s GM 4-speed? I have one and want to put it in my '55 but want to go through it first. Kit's appear to be real cheap.

Are there any parts that should be replaced regardless? It looks like the input shaft is one of those. Are there any resources (books) that I can follow to do it right?

Thanks in advance,

Mike

 

[Marks63PontiacGasser]

Boy, it's been a long time since I thought about the saginaws. One thing I remember is replacing the front wave spring washer (???? can't remember the actual name of it) with a torrington bearing. Some thing about the washer breaking and causing too much play??? One other thing that I was always going to do on the 4 speed Saginaws was, find an OD unit off of the 3 speeds and put it on the 4 speed to make a 4 speed overdrive. It's a bolt on addition but there was something about an actuation pin or something that had to be modded or?? I'm sorry for the lack of info. It has been 35 years since I thought about this. There should be info out there on GM boards etc. I remember them saying that the addiditon of the torrington bearing increased the strength of the Saginaws a lot. It was a major weakness. I hope the info helps and you can figure out what to do with. Mark L

 

[1946Austin]

From what I've always read the Saginaws were a pretty weak trans, basically a 3 spd with one more gear. Not ssure I'd put one behind a engine with any power. Had one in my '67 Chevelle and after putting in a new clutch, the first burnout I did imploded it!

 

[mt94ss]

Oh great! Maybe I'll stick with the 700r4 until I can afford a TKO 500 or T56. The last thing I want to do is put it together and break it on the first run... I guess I need to do more research.

Balloon deflated...

 

[Str8axle]

Sell the Sag and buy a Muncie.

 

[1946Austin]

Yes, a Muncie M21 or a very strong M22, but steer clear of the M20, it's stronger than a Saginaw, but not by much. A Super T10 would be a good choice too.

 

[mt94ss]

Why not an M-20? Isn't it stronger than a T-10? Here's a craigslist for an M20 wide ratio. http://portland.craigslist.org/wsc/pts/2446771550.html

I thought that M20s were wide ratio, M21s were close ratio, and M22s had straighter cut gears for more torque. It seems like a decent deal for a good trans. I did some research online and couldn't find any structural differences between an M20 and M21 other that wide and close ratio. Is there a torque rating for what these trannys should take?

Mike

 

[1946Austin]

Sorry, the M20 is the equal to the M21 in strength, I just don't care for the wide ratio.

 

[Str8axle]

When picking a M20, try to get one with a 1" counter shaft. The early 7/8" counter shaft trans are the weakest ones. But if the price is right, it'll suffice till you can score a better one. Still better than a Sag or T10 in my opinion.

 

[mt94ss]

After doing a bunch of reading about Muncies and decided on a M20. I found that the close ratio works best with 4:56 or lower gears. I have 3.73s. The lower 1st gear 2.56 instead of 2.20 makes for quicker starts with the 3.73 gears.

I picked up a M20 - wide ratio from '64-'65 - 7/8" shaft. It came with a Competition Plus shifter and the price was right.

The guys at Garage Motorsports said that this will handle the 400 HP no problem. I got the parts to rebuild it and will decide when I'm in it if I'm going to change it to a 1" shaft. They even got me updated synchros (late style) and the collars that go over the hubs that keep the tranny from popping out of gear when decellerating.

I will go through the shifter also.

Can't wait to get into it.

Mike

 

[Marks63PontiacGasser]

Mike. If you do a rebuild, would you do a project type thread either in projects or in this transmission section so we can all see and learn about doing the rebuilds. My first car was a '55 chevy with a transplanted 348, three carbs and solid lifters. It also had the early weak 3 speed trans. I'd blow that sucker every weekend and end up rebuilding or replacing it on Mondays. My old back yard is probably still full of the needle bearings that fell out. But that was 1968 and I've not had a manual trans apart since then. Would be great to see it again. Mark L

 

[mt94ss]

Will do, Mark.

 

[rlbutcher]

Hey Mike now that you got straghtened out on your trans GIT_R_DONE. heh heh

 

[mt94ss]

Hey Mike now that you got straghtened out on your trans GIT_R_DONE. heh heh

Hey hey! One of the last pieces of the puzzle. I have a scoop coming, too! (Thanks Jeff from trifive forum) looks like this :

Soon, soon, I will be able to put it together...

 

[1946Austin]

I think you'll be very pleased with the Muncie 4 speed Mike! I had one in my '67 Chevelle that after it got totaled went into my '55 gasser. I beat that thing to death with 6,000 rpm launches and it held it's own.

 

[Str8axle]

No complaints with my Muncie, if that helps you any

 

[Marks63PontiacGasser]

Well you will finally have a good Pontiac race part on your Chevy. Now it's gunna go fast. That is an early Ford truck air scoop from their big trucks. Pontiac bought them from Ford for their Super Duty Pontiacs in the early '60's. 8^) Mark L

 

[Str8axle]

I think I hurt my M20 today. Pulled a couple really good holeshots and now there's nobody home where second gear should be. I won't be able to pull the side cover off till tomorrow sometime. This should be interesting.......

 

[classic gary]

check the mid plate, i was street racing back in the late 70's and pulled a hard 1-2 shift, blew the bearing out of the mid plate, broke the drivers side axle, and broke two rocker arms all at the same time. the 70 mustang 351C with N2O, i was racing flat towed me home that nite !!! ( I had him till it broke).

 

[classic gary]

so how does the insides of your munchee look?