I’m going to swap in a 4-speed , what’s different from 350- 455?

So I’m going from a 350 auto car to a 455 4-speed Muncie, so I’ll be looking for parts, but I’m not sure what’s different from a 350 4-speed parts to a 455 4-speed? It all for my Stage 2 build, I want to make sure I get the right parts.

Thanks for any help.

 

Z-bar, ball stud, rod, fork. I'll have to look @ the assy manual but I believe it's basically everything from the end of the rod that comes off the pedal to the flywheel. Not sure if SBB uses a diff. throw out bearing &/or smaller clutch disk.

Shifter, shift linkage, back drive, pedals, NSS, clutch rod (pedal to Z-bar), steering col. etc. I believe is all the same.

A quick check of the assy. manual will show exactly.

 

Thanks for looking it up I don’t have an assembly manual. What splines does the tranny have to be on input and output to the drive shaft? Is the drive shaft different from 455 and 350?

 

IIRC '70-back vs. '71-up use a different spline count (350 & 455 used the same M-21 trans). I'll have to look @ driveshafts too bit I thought 350 auto/manual & 455 manual took the same length.

What trans are you planning on running? I'd probably run something heavier duty than a M-21 if you're planning on racing it and (e.g.) I think a M-22 is the same length but the M23Z is slightly longer.

 

I’m planning on M22 wide ratio with a 4:10 rear. I think the M22 is 26 spline?

 

Following. Will be undergoing the same swap this winter if I can sneak away. I believe I have most of the correct parts. I can get an inventory together and post up here. There are a couple of sticky threads posted that I’ve been cross referencing

 

OE M22 is close ratio (not sure spline count) - Are M20 type wide ratio gears avail? Why wide ratio w/4.10?

 

You can use all the 350 parts on a 455 but they don't look correct except for the flywheel...They function as well. I had a 350 4 speed setup in my 72 GS that had a 462 in it..Ran 11.99 and never died. You will need a 26 spline clutch for the M22 and a 455 flywheel minimum.The fork and pieces Dano said will be correct for you.

 

I can have a M22 built with either, with all the TQ I’m gonna have I think it’ll work great. I could be wrong but My 1970 LT1 Z-28 with it has a nice long first gear with 4:10. I am not 4-speed expert so that’s why I ask questions so I can rely on guys like you for what’s what. I’m smart enough to do that Atleast haha.
Thanks for all your input I really do appreciate it always. I’m dumb frequently!!

 

70 and older transmissions generally had 10 spline input and same as turbo 350 output shafts.

71 and later transmissions generally had 26 spline input and same as turbo 400 output shafts.

In either case, I think the 350 (my 71 35 definitely does) have a 10.5" clutch while I believe the 455 has the 11" clutch.

As far as converting, make sure your crank can accept a pilot bushing. Some later ones didn't get machined for it. If it isn't together yet, get the crank checked/fixed so there are no surprises.

 

Didn’t know about the crank, that would be quite a surprise.

 

I'm no expert but thanks. Buick used the close ratio in numerically lower geared cars than Chevrolet, which in some cases at least (e.g. '71-2 350) was a mistake IMHO. I assume the overall rationale was the torque. Not sure in the BBB or '68-70 350 whether a M20 would've performed better. Conventional wisdom would be that w/4.10s the close ratio would be preferred.

 

I’m not looking to bracket race, drive-ability is my main goal. That’s why I turned down an offer to buy the original 4:88 rear end the guy I got the Stage 2 pistons from.

Do you think an M20 is strong enough for a Stage 2?

 

In that case unless you never plan on taking it on the highway, I think I'd go w/ 3.55 or 3.73 in an 8.5 housing w/a tru-track carrier & either wide or close ratio should be ok. Wide would give you a numerically higher 1st gear so it'd feel like a higher rear off the line.

Who builds the M22 w/wide ratio gearset? I might be interested in such a beast. I'd be hesitant to put a M20 or even M21 behind a Stage 2 if you plan on getting any traction. I always thought the OE M21 behind a stock Stage 1 was marginal. I have a period correct (i.e. '70) M21 for my stock "appearance" 350 4-sp, which I do plan on running at the track, & I question whether it's up to the task which is why I asked who builds the M22 as the higher 1st w/my 3.91 rear might work well. I'd run 4.10 if it was an option in a '70 housing as that's probably the max. streetable gear but I'd also probably be more willing to run sustained higher highway RPM on a 350 than 455.

 

I just googled M22 and there’s several places that custom build them but not cheap about $3800. I myself may go with a 3:90 rear, just throwing things at the wall before committing to anything.

 

Auto gear out of Syracuse Ny is the company who has revitalized the muncie trans and gear offerings. Thats the best muncie transmission on the market today.

 

Thanks, great heads up.

 

Yes, I had an M21 in my 1971 GS 350 factory 4-speed car. It really sucked taking off. It felt like I was taking off in second gear all the time. It was so close in ratios that I often went from 1st to 3rd or 2nd to 4th. The gear spacing sucked for a torquey Buick.

I swapped in an M20 for a few years and it was MUCH better. It had the same effect as swapping to 3.55 rear gears.

I have an M23Z in my car with 3.08 rear gears. It is a really sweet transmission. Coming from an M21 to the M23Z was like daylight to dark. 1st gear on the M21 is literally 2nd gear on the M23Z. That transmission makes the 3.08 rear gears launch like 4.11s compared to the M21.

For a Buick with lots of torque, the wider gear spacing is not an issue, even for my 350.

 

Hopefully can actually take a ride in it this year plus want to look underneath and see how "stock" is looks. My 2023 Nationals was very abbreviated.

My thinking on the wide ratio was more the lower 1st gear than the spread. The problem on my last 350 4-sp was always getting off the line. It ran 104 MPH but only 14.0. Of course may have been my technique or lack thereof as well. It was pretty consistent though and would run 'em down at the top end.

 

All that autogear stuff will work with a stock case muncie, but thats kinda like taking your sister to the prom...