Technical Questions about Muncie to TH350 swap.

I recently sold my Cometkazi truck to a friend of my wifes. She thought she would be OK with the 4 speed but now she wants me to swap it out for an automatic. So I have a few questions maybe you guys can help me with. I'm pretty sure it will use the same crossmember mounting location but, looking at store bought TH350's I see 2 options on the tail shaft length a 6'' and a 9" which one would be the same as the Muncie so I wouldnt have to change drive shaft length? It looks like Summit sells a TCI street fighter, they also sell a Performance Automatic brand for about the same price and I see B&M has one but Summit doesn't carry them. Does anyone have any experience with these ready to run 350's or have any recommendations? Its a mild blown 327 probably make 450 or so HP at the flywheel 2400 pound truck with a 342 gear. I figure I will need a flexplate, converter, trans, lokar shifter, dipstick, transcooler and lines and about 3 gallons of fluid. am I missing anything else?I'm kinda bummed she wants to do this but its hers now so its her call, I just think its way cooler with the Muncie, Thanks in advance Mike

 

I not positive but I kinda remember there are 3 tail shaft length for a TH350. You need the shortest one. And then there is a fine spline and course spline output shafts so you driveline might need a different yoke.

 

Gee Honey , I can't find a good auto , Hey , do you know how expensive that'll be ? , I'll have to cut up the chassis to do that , I won't be able to hook up a speedo , We'll hav to buy a new radiator......Just a few I could come up with....Do you realize how much that'll de-value the truck ?

 

I believe you are thinking of PGs . One spline...same as Muncie

 

Well, that's a bummer. I don't have any good answers for you Mike. I usually chuck those automatics as quick as I can. I do remember ditching a powerglide in a 68 Camaro in favor of the Muncie. It bolted right in. Will you need to swap the radiator to run a trans cooler line?

 

Oh, and is there enough clearance in the floor or will you have to make the tunnel bigger?

 

I told her when she bought it I would switch it over if she didn't like or couldn't drive the 4 speed. I don't know what she did or how but her left ankle is all swolen after driving it to and from Torque Fest this weekend.

 

This doesn't answer the OP's specific question, but possibly info that can help. Just did the opposite swap in the OT '72 El. Removed the short tail 400TH and installed a Muncie. Same length,but the crossmember had to be flipped around so the pad reached forward. Also had to swap driveshaft yokes.

 

Now I'm a bit confused. The chart above shows the Muncie total length to be 29.3" and the TH350 to be 27 5/8" (6"tailshaft) I thought there was one that was a direct swap, (same trans mount and driveshaft length) am I wrong about that? I have swapped a few autos to Muncies and don't remember having to have a driveshaft made but it's. even a long time maybe I'm remembering wrong?

 

All the direct swap transmissions are "slightly" different in lengths but the splines on the yoke are usually long enough to make up the difference. Same as when you lower or raise a vehicle and the splines stick out a little further or a little less. Since you are going about 1.5" shorter, you should not have any problems with the yoke sticking out further. If it does not engage into the transmission far enough to make you comfortable, you can get a longer yoke and just swap out that part, even can be trimmed to fit.

Also these are the best 1-800 transmissions in my opinion.

http://www.phoenixtrans.com/

 

I am with you. Pull a 4 speed ? Give her a sport utility and inform her she is not a hotrodder.

 

I'll check them out Jeff Thanks

Normally I'd agree with that, but after living through this horrible crash and then having her A coupe run off into a ditch on the interstate and break the front axle off. AND still want to not only get in one of these things, but drive a 2400 pound car with a blown small block Chevy, I'm not going to argue with her about her ankle not being able to push a cluth pedal down.
.

 

I stand corrected. Open mouth, put in foot. How do I always manage to slap myself in the face ?

 

Ran into the similar thing with my sister's Camaro. Due to back issues, 4 speeds are out, and it's automatics only, so her Camaro has gone from PG to T350 to 200R4. The 200R4 has a 1st gear lower than a T350, a .6 OD/lock up converter, and most all are dual bolt pattern to fit Chev and B-O-P-C blocks. It's been a while, but I remember the mounting pad and driveline/yoke being the same for a short tail Muncie, PG, and T350.
While the PG, T350 and 200R4 tail shaft length are fractions of an inch of each other, the pad location on the 200R4 is the same as a Camaro T400 and required changing the crossmember out for the stock T400 Camaro crossmember I had been hoarding. I might have had to use the T400 yoke too, but (to quote Hillary Clinton) I don't recall. Just don't forget, the 200R4 has a reputation of not being very strong stock and you'll probably want it to have it built up by someone reputable if you're going to put a lot of power (torque) through it, even if it's from a Monte SS or Buick turbo car. Supposedly can be made stronger than the 4R700, though.

 

No, you're fine. I'm still trying to talk her out the auto myself. I'm going to try one last ditch effort and try to modify the pedals to make it easier before I concede myself. She's been known to answer to "Pussyfoot" because her legs are so short her feet smell like pussy....

 

I built the chassis from scratch and moving the crossmember rearward would be a giant pain. If I do put an Auto in it simply for ease of installation I'm going with a TH350. That's why I'm asking about a direct swap out. I want to be able to use same trans mounting and Drive shaft length.

 

Centerforce clutches are easier on the leg.

 

While it's not a center force, it's not a heavy spring clutch, it's actually a fairly easy diaphragm pressure plate and Custom made 6 puck disc.

 

...she should leave it alone and buy another car,...then sell this one,...
...did her A get totalled?,...or will it be rebuilt?

...if you go with the auto, just mount a trans cooler on the framerail beside the trans, long as it's in an airflow it'll work just fine.

 

I fixed her A Coupe but she was afraid of it after that so we sold it. She is dead set on driving the Cometkazi truck still

 

I pulled a TH350 out of my high school 1969 Malibu, and put in a M21. I do not recall moving the crossmember, and I did not change the drive shaft. I do not recall what the tail shaft length was, but if someone else has that detail, that is what works. The holes in the mount pad are slotted, so a bit of change can be accommodated. You might need to slot.

Also, if I remember correctly, the mounting pad on the TH350 is on the main case, so that does not move, regardless of tailshaft length.

 

I want to say that it was the 6" tail housing, which I think makes sense.

With a 6" tail, a TH350 is 27.625".

A Muncie/Saginaw is 28.3", for a difference of 0.675".

 

Short shaft TH350 (6 inch extension housing) will bolt right into/onto your existing crossmember transmission mount, and the speedometer cable should be the correct length. Takes the SAME slip-yoke. As long as you use a flexplate the same diameter of your current flywheel, you can even use/keep the existing starter motor.
I am Butch/56sedandelivery.

 

Thanks fellas! That's what I was hoping for. My driveshaft now is pretty close so as long as the TH250 is the same or even a little shorter I should be golden. I still hate to do it to the truck but it's hers now. I'm still going to do a pedal extension on all 3 and hope that will help make it easier for her and she'll change her mind about the automatic. Maybe even install a line lock for her to help on hills?

 

You know if you put in a automatic with a reverse Manuel valve body and a nice stall you can have a bunch of fun.
Mike Have you tried a hydrolic throw out and centerforce diapham clutch. I had to change mine over in the 68 bronco for my wife. It helps but in stop and go traffic no stick is fun .

 

Your last post Russco, you said TH250; are you now going with a TH250, or is that a typo? TH250 will fit the same as a TH350, but is weaker. Just so you're aware. I am Butch./56sedandelivery.

 

Yes it should read TH350

 

I full and well realize that some of the previous posters think that it is a total sacrilege to change from a 4 speed to an automatic but my left knee keeps telling me that it is getting damned tired of pushing clutch pedals. I'm still planning on 5 speeds for both the 48 and the model A but that may change if I have to have my knee replaced.