Street Driving an M21 462ci
 

Hey guys, I’m in the process of building my 74 TA and wanted a 4 speed. I picked up a fine spline M21 but I hear they need a ton of gear to make it fun to drive. Should I just look for an m20 to replace it with. I think the rear gears are 3.08’s. Thanks guys

Both the M21 and 22 have a 2.20 first gear .

How is your 455 Cam’ed?

How tall are your rear tires you have or will be running ?

Since a 455 has such a wide and flat torque band when Fitted with the right Cam a wide ratio trans is not a handicap.

2.54:1 posi gear is fine. All that matters is your throwout bearing be Hydraulic.


If you use the stick mech fork trow deal, thenthe 455 TQ will readjust you pedal setting on every fly.

RA iv HFT, 231/240. Tires probably 27” tall

I absolutely would not run a 2.20 1st gear with a 3.08 rear lol

If you're dead set on a 4-speed you'll be happier and better off with an m20 with a 2.52 1st gear or change the rear gear to something better suited for the 2.20

i have a 505 with a 3.55 gear and an m23 super case with a 2.98 first and i still want more first gear. sorry but i just love letting the clutch out and the engine barely notices. makes it so much easier to drive up a steep gravel driveway or inch along in traffic.

big pontiac tractor motors with automatic transmissions do really well with tall gears. but for a stick shift, i still say get that thing moving with as much gear as you can!!!

Definitely get the M20.

Might think about getting a 3.23 rear to go with it, like the factory did with every ‘75-‘76 455 Trans Am of which all were wide ratio 4-speed equipped.

That seal it, M20 or ST10.

I have now a tkx 2.87 first gear and 3.31 rear,,,its much more pleasurable on take offs compared to the m21 but even though that sounds like a big jump in 1st gear it actually feels normal. I wouldnt want it any taller.Not geared too low. So i would imagine a m20 compared to a m21 would feel nicer on takeoffs but its not going to feel like a big change but with a 3,08 rear i would definitely go with the m20 at the least. Its still going to feel a little tall in 1st gear. I think the tkx comes in a 3.25 first gear,,wonder how that would be.

Wasn’t the Borg Warner ST10 used during those years? Probably used the 2.43 first gear on those cars with highway gears. Anything less will not be enjoyable.

I agree, even a 2.52 with a 3.08 isnt ideal but the op isn't giving any other options. I typically set them up here with a decent amount of first gear multiplication, it's just much more pleasurable to drive as already mentioned. Especially driving them as much as I do, 10,000 plus miles a year. And in most cases these days many don't even mess with the 4 speeds anymore and go right to a 5 speed to enjoy highway cruising as well. This opens up both ends of the spectrum. Now you can have your first gear, and even better gear multiplication through the other gears if you setup a proper rear gear, and still go to sleep on the highway. It's a win win.

The BW super T 10s used in Pontiacs from 75
Are good for handling a solid 450 hp motor being bolted to them.

Here’s the ratios they could be had in.

All Pontiacs from 75 on used the standard wide ratio model, however late 70s Chevy Z28s used the special wide ratio model .

Personally, I like the 2.64:1 first gear. That is a nice compromise for a heavy street car with a low numerical rear axle. They also put a 2.88:1 first gear in a super T-10. I wouldn't be afraid to try that either. I like the super T-10. I feel it has a better shift feel and is more positive with a superior side cover design and more robust shift arms and forks than a Muncie. Most on the forum would disagree with me though.

The 3.27 first gear with a 3.08 rear sounds like a good combo but yes not what he’s asking about. If someone can afford it though the tkx would be my choice. What are you going to spend on a nice m20?

Here’s my experience with higher geared rear ends.

I have 3.08’s/M-20 (2.52 1st) 4-speed in my ’70 Lemans 4-dr. that weighs 4000 lbs. with me in it. The engine is a .040” over 400/462 stroker with a RAIV 041 ‘clone’ cam with 1.50 rockers from Bullet (circa 2009), 6X-8 heads with SD CNC porting (255/210 cfm) with 9.5 compression, factory iron intake/Q-jet, and repro RA manifolds. It has no problem pulling away from a stop without excessive clutch slipping with the 7.76 1st gear multiplication, but a steeper 1st gear would be welcome…somewhere around 2.80 would be nice. I like the 3.08 gear for cruising.

I also have a ’71 455HO GT-37 with a BW-ST10 (substituted for the original M-13 3-speed) with the 2.64 1st gear (from Jim Mino) with the original 3.31 rear axle (8.74 1st gear multiplication). The 455HO is .040” over (464 cu. in.) and all stock except for a Summit 2802 cam. The stock heads 197 HO heads flowed 230/175 cfm and compression is only 8.61. It loves the 13% steeper 1st gear to overcome the full point less compression compared to the 462 in the Lemans.

It's interesting that 455HO ’71 A-bodies would come with M-22/3.31 gears when equipped with A/C. That’s only 7.28 1st gear multiplication! The ’73 SD-455 Firebirds were factory equipped with the M-20 wide box instead of the close ratio M-22 to overcome the even softer low-end torque with the ‘Y’ cam (8.62 1st gear multiplication).

Dennis

I can give you a couple price points from the last 2-3 years. I have built 4 Muncies for friends/customers. Swap meet wide ratio boxes in usable condition seem to run $700.00-$1000.00. That doesn't mean they are good necessarily. Just usable. Of the 4 brought to me for overhauls, 2 were able to be rebuilt with small parts kits, 1 or 2 synchronizers replaced and 1 or 2 gears replaced. New brass of course and gaskets. Parts average cost around $400.00-500.00. One just needed a small parts kit, brass, speedo output gear and gaskets. About $200.00 for parts. The last one was an M22 from a big block Chevelle. Almost every piece in it was destroyed. Only parts I could reuse were the case, side cover, and main shaft. Even the tail housing and bearing support needed some welding and repair! He wanted to keep it numbers matching so I fixed it. Had $1700.00 in parts. New gear set was made in Taiwan and was very nice I am happy to report. I generally charge around $500.00 labor for a basic complete overhaul of a Muncie. Not including welding and other strange problems that sometimes come up.
So if you have a Muncie that is all torn up, a TKX does enter the conversation IMO.

I have the original M21(2.20) and 3.42 rear in my TA, while it is useable, it is not a great, street friendly combination. I have a rebuilt M20 that will be going in this winter. I would prefer to do a 5 or 6 speed swap but they are so pricey. Plus if I’m honest this car does not see many highway runs, certainly not long ones and probably never will.

I don’t think even a ST10 has a low enough first gear for a 3.08 rear gear. If I had 3.08 rear gears I’d look for a aftermarket M23 with a 2.99 first gear or get a M21 /20 rebuilt with the new extra wide ratios swapped in it.

Then you would have the best of both worlds great first gear and reasonable highway cruise rpm.

The ST-10 I got from a 1980 Z28 I think has a 3.42 first gear. Stout 383 SBC and a 3.73 autocrossed the crap out of it with road race slicks!

But I know Larry Navarro who posts here sometimes grenaded a ST10 in his 79 TA with a medium 455., not even power shifting when it went.

Until the 454/455 came along wasn’t it recommended /required from Gm that it was 3.90 and up for the m21 trans?

I have a 74 Trans Am with a 455 / 4 speed Muncie and 3:42 rear. I find the car enjoyable around town but highway driving is annoying. I got spoiled by my daily drivers with multiple overdrives. I know most of the people on this board are very nostalgic and like 4 speeds, but maybe the original poster should consider a TKX. I think it would add to a more positive driving experience. I know in my case its the perfect solution to my issues with the cars drivability.

I found a super T10 from Richmond at a decent price I’ll be putting in with the 2.64 1 st gear. It’ll be a local car, no real long trips. I’ll have 27” tall tires, so combined with a 3.08 or maybe a little lower but nothing lower that 3.42 I should be fine. I just wanted input on the m21 with the 2.20 1st gear but it’s definitely not staying. Looking for a fun cruiser, nothing more.

Mgarblik is pretty much spot on. Out here I see them regularly for $800 to $1500. Some claim rebuilt but are they really and by who? Did they just do the minimum? Some guys don't even want you pulling the side cover to have a peek. So you really can't be sure what your getting. And if you have to rebuild it, not counting labor you can spend several hundred in parts.

It's pretty much why I just keep what I have and don't go out of my way sourcing 4 speeds, and save that process for the correct type restorations. Most everyone these days that actually want to drive their cars just go 5 speed. The cost isn't much more when you really get down to it and it opens up the cars ability and makes the whole driving experience better.

I think it's a 3.27 1st gear in that TKX and that would be a nice combo with a 3.08 gear. I have the same TKX and rear gear as you do and I agree with everything you said.

Just to add the other really annoying thing with muncies, st-10's etc.. is that most won't go through the trouble to do a case repair at the counter shaft. You won't know it's a problem till it's in the car and drive it a bit, it's common for them to leak there from just years of use and abuse. The cross pin doesn't fit tight enough anymore and with these things being 50+ years old the problem is more common than you think.

I've said it before. Of all the modifications/upgrades I've done to the car, the TKX was one of the best. I know the OP was not considering that option but if it was within their budget, a 3.27 1st and a .72 OD would be the equivalent of having a M20 with 3.99 rear in 1st and a 2.21 in 4th. It's a huge improvement in driving pleasure.

I've had TAs set up with a few different engine and trans combos, and it really isn't the big of a deal to me what it has when it comes to street driving. If we're talking about a car that's going to see the track 99% of the time, of course we should be scrutinizing every gear ratio possible, but something that's just a street bruiser/cruiser I feel it's not the big a deal.

If it were me, I'd throw the M21 you already have in it.

my builder is almost finished w/ a 461 that was started nearly a year ago. besides waiting for porting to be finished then pistons and cam .. it's been a haul.
car's original m20 was popping out of 3rd on deceleration so I had transmission rebuilt w/ "Italian" masiero m22 gears but w/ wide m20 ratio. car currently has a 12bolt w/ 3.73s. previously wasn't too great on the highway ha but super fun around town which'll be mostly where it'll be living.
to say I'm looking forward to getting motor back in would b a huge understatement ; ) im not against going to lower numbered gear next spring but will drive as is this fall for sure.

Not to hijack the thread, but related. A number of people in this thread have done the change to a TKX. Is anyone willing to disclose the "real total cost" to make the conversion?. I know you can buy the transmission alone for $2800.00. But that's just the tip of the spear. Once you modify the crossmember, have a driveshaft made, figure out the transmission mount, buy a new clutch with fine splines and all related components. Then the shifter and whatever is needed to go with it. Also a working speedometer. Are we talking more like $4500.00 if you do most of it yourself? I like the idea, just haven't been able to pull the trigger.

It depends on the car. I can do a typical f body or a body for $3500-ish. It depends on what the owner wants.

I can shorten driveshafts and rebalance cheaper than new shafts, but if you want a new shaft we may as well upgrade it to seem less steel tube and better ends so it'll at least take a little abuse. Those shafts run $600-ish with solid Spicer joints.


Clutches I can just simply put a 26 spline disc in and leave the rest of it if it doesn't show issues, that's about $100 for a disc. I find most owners want to change the whole clutch, now you're getting into $500-$600 additional. Then they want to add hydraulics when the mechanical is perfectly fine.

Cross members I modify unless you want something aftermarket.
Speedo is easily handled with a short cable extension and adapter for the Ford style speedo gear. Some guys just want to change out the whole thing or use a gps setup for a fancy speedo, all that stuff just adds cost. Most of it isn't necessary.

We are talking about 4 speed cars here, much cheaper to do that swap.

For instance my 69 Z28 is a factory m22 car. Since we drive it everywhere including my wife dailying it fairly regularly, I wanted the 5 speed to mainly cut down on the wear and tear. It's a simple drop in with no modifications.
Since it was a fine spline I didn't touch the clutch. I didn't want to modify the original driveshaft so I had a nice steel shaft made with solid joints $600. I didn't want to modify the factory cross member so I bought a drop in aftermarket piece, $300. A simple speedo cable extension and a round bar shifter to look like the factory piece pops up in the stock console perfectly. Didn't cut a thing on the car. I had it all done in a day. At the time the tko was $2200. I was in the whole thing with tax and all for $3400-ish and considering what it did for the car it was well spent. The 2.87 1st gear really woke it up and the .64 5th allows me to cruise 75-80 mph at 2300. Darn thing knocks off 21 mpg and is super nice on long trips.
I own other 5 speed swaps that cost more as they get more involved but again, I'd gladly spend $4500-$5000 to do these swaps just because the driving experience isn't even a comparison to anything less. I still have another one I'll do when I get around to paying attention to that car more. It's another 4 speed so pretty straight forward.

When I can tie up $2000-$2500 in a Muncie and it doesn't improve anything it just makes more money sense to do the upgrade.

Ive even gone the auto overdrive route on some of our other cars and kick myself for not doing those sooner. That gets a little more spendy.

The TKX is $2895 everywhere. The best deal is free shipping and $70 summit bucks at Summit Racing. (The 10% coupon is not valid for transmissions) If you have an existing manual trans, 4k should get it done.

Yes total costs can vary on what you change. Instead of modifying a driveshaft which I’ve done before , I bought a 700.00 Denny driveshaft…. So more money. I also went new billet flywheel and clutch ,,, more money over using what you got. Adjustable bell housing dowel pins. New shifter, used my factory Speedo cable.. Energy suspension had the correct height trans mount for the A body..Yep I’ve got over 4 k but it can be done cheaper.

Yeah that's the problem with everything anymore. It's all climbing in price, and it's not just new parts, it's swap meet parts, used stuff, nothing is immune anymore. So the longer you wait the more its going to cost. I fully expect tkx transmissions to surpass $3000 in the future, but you'll also be paying more for muncies too, not just to buy them but to rebuild them as well. The car hobby isn't for the faint of heart anymore.

I just put a 2.88 first gear ST10 in my wife’s car. 3.07 rear & 27 inch tires.
It finally drives like we wanted it to. Nice around town & 70 mph is OK on the highway.
It’s a 9-9.5 to 1 comp 455 with 230 / 236 hyd roller. Couldn’t send the dough for an overdrive. I would not have liked a 2.20 first gear at all.

ETA, if it were me. I’d sell the Muncie & get a trans with lower first gear. Hey wait, that’s what I did. ��

I just rebuilt and installed a 3.07 12-bolt in my friends '65 A-body with a Muncie M20 and a 462/RAIV cam and the car drives fine. No issue with takeoff in first gear.

The M20 with 2.52 1st is higher than us auto TH400 with 2.48 first gear. Seems like a nice comprise is M20 and then if you're still on the factory rear end, you probably need to change the axles at some point. Rock out some 3.73s etc and you'll be real happy with the tires spinning like the rest of us.

Thanks for the pricing information. Very helpful. The car I may eventually swap to a TKO is a 62 Catalina. So no drop-in parts for that one. Currently a 10 spline input Muncie. They have a very narrow trans tunnel for the Slim Jim trans so even a Muncie is pretty tight in there with the shifter hanging off the side. The exhaust goes over the cross member so it's tight as well. For a big car, not much room under there. Even the clutch linkage is jammed in tight because of the rear steering gear and linkage. Something to think about though. Would love the OD with the 3.42 axle.

Thanks. That was a mistake. I meant TKX. It looks like it would package easier and has a bunch of different shifter position options.

In 1971 didn't the 455 HO Judge have a M-22 and 3.08 factory installed rear gear?

I think most had 3.55 gear?


:confused:

For just street driving and no sticky tire high RPM launches I would get the 3.42 first gear ST-10.I have one in my 62 421 GP with a 2.64 rear.No slipping the clutch,just kind of change feet.I also had one in my 421 63 GP and did race it a few times with street tires and it held up fine.It had 3.08s in the back.NOT and good trans if your going to beat on it a lot.The lower the first gear the lower TQ rating the trans has.Tom

I picked up a Richmond ST-10. Will be a while before the car moves on its own. Still building the long block.

What 1st gear ratio ST-10 did you get?Tom

I believe 3.31 was the highest gear (lowest numerically) you could get that engine/trans combo with AC, 3.55's std. w/o AC like johnTA1 said...3.07's with the TH400 auto with AC in A-bodies, 3.55's w/o AC. These are the std. gear ratios you got without ordering a different ratio option.

Dennis

2.64 first gear

That ratio is not going to help much over a M20.2.88 or the 3.42 is what you want.Tom

I have 3.08's with a 1964 2.56 1st gear M20 ends up with a 7.88 effective ratio and run 27.2" tires. Works fine.

2.52 Muncie ends up with a 7.76 effective ratio

2.64 ST-10 ends up with an 8.13 so should be more than fine.

I found this in my library I had printed up for ST-10s
http://www.pontiacpower.org/BW.htm