NOM61

Anyone made this conversion?
I'm thinking of swapping my pos "rebuilt" M20 for a low mile new build Richmond ST10 wide ratio (2.88) that a C3 forum member is selling.
I know I would have to swap the clutch disk and the yoke but what I am not sure about is the shifter, linkage, and transmission mount.
I found a thread where the swap was made on an early C3 which mentioned length issues (ST10 is 3/4 inch longer that an early M20?) and swapping out the drive shaft. The thread I found also mentioned mount holes not matching and I don't know whether the shifter will mount or if the linkage would need to be modified for clearance.
I would appreciate any input!
Thanks!

DT

P.S.

Found a few threads with C1's "thinking" about the swap as I am, but none that actually did the deed except perhaps Vettrod, but I believe he has one of the rare nodular case ST10s and no install details given.
Did find a 66 that did the swap and it involved shortening the drive shaft but few other details given.
Definitely appears it will require a new shifter and linkage.
Beginning to think this will just be another "thinking about installing an ST10" thread that ends with a Auto Gear M22, my first Muncie rebuild or a Keisler 5 speed being installed instead!
The RS400/3.36 combo IS mighty tempting! Don't have the torque to worry about like the big cube boys so I can't see the need for the 500..

larrywalk

I swapped a Super T-10 into my '65, replacing the M21 Muncie. The trans fit perfectly; as you stated, the clutch disk needs swapping for a 26-spline vs the stock 10-spline. Also, the output shaft has 32 splines versus the 27 spline Muncie; use a yoke for a '75-'79 corvette with 4-speed.

The stock driveshaft fit perfectly - no need to shorten it; the trans bolt holes aligned exactly, the trans mount worked perfectly too.

Shifter wise, I use a Hurst shifter for the '65, but the stock shift rods do not fit. With a quick call to Hurst tech, they sent the proper rods for installing the ST-10 into my C2.

With 3.70 gears, the ST-10W ratios with a 2.64 first gear for a 10:1 total ratio are perfect. If you have a 3.36 rear end; the ST-10Y (2.88 first gear) will be perfect, and nearly so with a 3.08 rear.

DZAUTO

If you already have a Muncie in your 61, then I'm guessing you also have the 62 (one year only) tranny mount adapter plate . In 62, because of the change in the tranny mount, the factory installed 1/8in spacers between the X-member and the tranny cross member. I went a little further with a Muncie in my 56 and made spacers from 1in square tubing. With the longer Super T10, this for sure is going to INCREASE your U-joint angles. I would REALLY encourage you to put spacers between your X-member and the tranny cross member.

Here's my tranny mount with the 1in spacers.





Tom Parsons

Dan Hampton

The 32 spline main shaft Muncies have the exact same dimensions as a Super T-10; the earlier Muncies are 3/4" shorter and take the TH350 style yoke.
__________________

NOM61

Thanks for the replies!

Tom,
I have an early model M20 (no ring) with the 62 adapter plate and spacers (washers) installed (thanks to reading your previous post on the issue!). I didn't go the full inch like yours - more like 1/4". Sounds like increasing to an inch with the ST10 would be a very good idea.

My biggest remaining concern with the ST10 is the shifter and whether the linkage would require any fabrication. I'm guessing that replacing the extra-long 27 spline C1 yoke with a (shorter?) C3 32 spline yoke will absorb the 3/4" length difference without requiring the driveshaft to be shortened?

The M21 that was installed when I bought the car had a Hurst shifter with a welded shift lever which used an adapter plate to mount to the M21. I shelved it when I installed the M20 in favor of a Paragon T-10 repro shifter. Would this Hurst shifter be a direct fit for the ST10?

Right now I'm considering three options:

1. Richmond ST10

Positives:
Low cost for tranny
New construction - not reconditioned
Very low miles
9.7 launch ratio w/ 3.36 diff -

Negs:
Additional cost for clutch disk, linkage and potentially shifter (seller will include his yoke)
Additional work, potential fabrication to install
Long term durability compared to Muncie/T45/TKO?

2. Auto Gear M22Z with 10 or 26 spline input and 27 spline output (from Paul at 5speeds.com).

Positives:
Simplified install with 10 spline input
Virtually indestructible with this engine, esp w 26 spline input
All new and improved construction
10.0 launch ratio w/3.36
coolness factor/gear whine
"Feels right" for 302.

Negatives:
Almost double cost of ST10, even more with 26 spline input
Same shifter/linkage issues as ST10?
Gear whine! Could be like side pipes - so cool at first and so annoying in the long run.

3. RS400/500

Positives:
Simplified install with RS400/10 spline
11.3 launch ratio/<2200 rpm @75 w/3.36
Improved cruising comfort/gas mileage

Negatives:
T45 - no infrastructure support for new/replacement parts
Even more expensive than M22Z
Purchase process/wait time
Unproven durability in this application


Overall, I think the real cost is a wash for all of them. The most expensive to install (RS) probably improves the desirability/resale the most and creates significant fuel savings. The M22Z also improves desirablily and value, but is it more, equal or less than a 5 speed?
The ST10 would be a very slight improvement in desirablity (if that) I believe over a properly rebuilt M20.

Rebuilding the M20 or converting the M21 on the shelf to an M20 or M22 would be another option, but if I'm installing a 3rd tranny in this beast, I would really like to improve the launch ratio. The current 8.6 with the M20 is ok (only very slightly worse than the classic M22/4.11 launch ratio of 9), but it would be much more enjoyable closer to 10.

Opinions? What would you pick if it was yours? In good weather I drive the car approx 150 mostly highway miles/week. Drivable weather in Vegas is about 8 mos/yr without A/C and heater. 10 mos when I finally get around to installing the Hotrod Air. 12 mos if I ever buy a hard top. I bought the car to drive it, and do so at every opportunity - wind/rain/temp allowing.

Estimated total costs: ST10 - $1400, M22Z - $2400, RS400- $2900.

As usual, I apoligize for the book.

DT

wmf62

OD and launch ratio....
Bill

vetrod62

The ST-10 I have experience with is in my buddies 61 vette. It is a "Speed Shop" over the counter cast iron piece with 10/27 splines and is Pro Shifted (No synchros). Two sets of shifter mounting holes like Muncies have. I have only seen stock ST-10s with the forward set of holes. Solid axle cars use the rear set of holes for the shifter. There may be tail shafts with both sets of holes, I do not know.

As mentioned earlier, the shifter arms are different and maybe the reverse rod. If you are doing 150 miles a week, you need a 5 speed.

I have a TKO-600 with less than 200 miles for sale. Jim

1COOL60

I have a '60 that is currently running a MY-6 overdrive transmission. For many years I ran a wide-ratio T10. Rear end is 3.36.

Switching to the OD was great. If nothing else, the reduced engine RPMs on the highway made it worth the trouble, which wasn't that much. It also reduced the oil comsumption a little, in addition to the improved fuel economy.

I agree with Jim. For all the driving you do, go with a 5-speed. I drive mine 3000 to 5000 miles per year, including at least a couple of (relatively) long trips. I have an RS600 on order; should be here by the first of June (per recent conversation with Shafi). Really looking forward to getting it in.
160

wmf62

i find it interesting that you are giving up your MY6. for a driver, i don't see the need for 1 more gear to shift....

how come?
Bill

1COOL60

The gear ratio spread is too wide for me. I like a close ratio tranmission. That 3.09 first gear is a little too deep, even with a 3.36 rear. The MY-6 is a truck transmission, and it shifts like a truck transmission, at least to me it does. Couple that with my trans is needing a rebuild which, of course, would be way cheaper than a RS600, but I still want that additional gear. I like shifting gears.
160

wmf62

i understand... i also have a MY6 with a 3.36 rer and the 1st gear is fine for me (3.09 x 3.36 = 10.4) and both my LT1 and my ZZ4 didn't/don't mind the drop from 1st to 2nd. to me, it shifts every bit as good as a muncie and is a stronger transmission (that basic trans was used by Chrylser behind the hemis). and around town i only have to shift twice...

the only nitpick i have is that it is reluctant to downshift to 1st at much higher than 20mph..
Bill

vettsplit 63

When you said 32 spline input, I'm assuming that was a misquote.

I don't know how much room there is on a C1, but I bought an M22 and had to make sure I got the small tailshaft, -27 spline output, for my 63. There is not enough room for the later 32 spline output.The tunnel is just way small. Just thought I'd mention that.

wmf62

a M22 is just an M20/21 with different gears. trans size should be the same.
Bill

vettsplit 63

Actually there are two different tailshafts. The early M22's used the small tailhousing and 27 spline output. Starting in 69 I think, the tailhousing went to 32 spline output and is physically a bit larger.

NOM61

Oops! Sure was! Corrected now. I would definitely be using the 27 spline output if I went with the M22Z.

Trying to decide whether I really care about OD or not. Turning 3k on the freeway for a max of 20 miles at a stretch just doesn't bother me at all. Heck, the 302 is just starting to get HAPPY at 3k and I REALLY don't care about the gas mileage - wouldn't own this car if I did. With the "Z" I could always swap in 3.08's and drop almost 300 cruise rpm and still have a 9.2 launch ratio. Wide ratios don't bug me either. Its just a better excuse to wind out each gear a bit further! I usually granny shift around 5k anyway when in traffic.

Bill's MY5 would be a good option but I don't want to have to pitch my new McLeod scatter shield as part of this install.

So the only reason left for a 5 spd is the impact on potential resale. That's what I'm trying to decide whether I care about or not. I'm leaning towards not. Caring that is.

Really hate dithering... will reach a decision this weekend and get an order in Monday.

DT

wmf62

there were 2 bellhousing bolt patterns for the MY6, the one i use has the standard chevy bolt pattern, BUT you have to use a bellhousing with the BIG (i believe it's 5-1/8") bearing retainer hole; so i suppose you would not be able to use your bellhousing without having the hole enlarged or turn down the bearing retainer...

Bill

NOM61

From McLeod:

"8630-M GM 1955-1981 ALL ; Same as 8630. Center Bored out to 5.125"

I'm guessing that a driveline shop will want a bit more than the $22 difference McCleod charges! Would this be a typical service any driveline shop would do? Doesn't seem likely my engine machine shop would have the proper fixture.

DT

wmf62

probably... but the first thing you would have to do is find a MY6... then, you would have to make an adapter plate for the hurst shifter to mount to the tailshaft housing, then the hurst's shift rods will have to be modified.

if you can do this, then i think the MY6 is a great transmission..

Bill

street62

My 62 came with a t-10. I have had many transmisions. 1st desine super t-10 with an iron case and the 2nd disine super t-10 with an iron case also a 2.88 first gear. I used a hurst comp plus shifter , I had to make an adapter plate out of some 3/16 inch steel that mounted on the trans first with som flat head cap screws, then drilled and tapped holes to remount the shifter in it's new location.I had to get a new yoke that was for 32 spline and made a new drive shaft.

NOM61

Just the man I've been looking for!
Did the 32 spline yoke create any clearance issues and did you have to shorten the drive shaft or just change out the yoke and u-joint?
If the 32 spline yoke clears without mods, an ST-10 will be going in if its still available!
Thanks for the info!

DT