Manual Transmission Install Issues

[SBC RACING]

Hey Guys,

I'm in the process of swapping out my SM420 trans in my 62 shortbed (w/ small block) for a Muncie M21. I'm at the stage where i'm mating the transmission to the engine and the transmission only wants to go 3/4 of the way in and stop. I've done a couple trans swaps in the past and have had the same issue where the trans goes 1/2-3/4 of the way in and i have to struggle with it until it eventually goes in. This time around even after fighting with it for an hour or so it still won't budge..

Just thought i would see if you guys had any tips or tricks before i fight with it some more tommorrow.

Any help is appreciated.

Thanks so much

[jbgroby]

OK I had the same issue with a tranny swap from a sm-320 (3 speed) to an sm -420 (4 speed) When I had re-painted the engine and trans I had gotten paint on the flange where the trans meets the bell housing. ALso some rust will cuase this to happen also. You would not think it would matter but the tolerance is SO close it does. Sand and clean the parts well.

Jake

[markeb01]

One thing I've found that helps is to come up with 4 long bolts the same thread size as the transmission to bellhousing bolts. They should be the same length as the pilot shaft, if there's enough room in the vehicle to use them, or as long as possible. Cut the heads off and cut a slot in the end so they can be installed in the bellhousing with a large screwdriver. Then slide the transmission over the bolts. It really helps make sure everything is lining up, and prevents bending the clutch plate when your arms get tired or the jack slips.

The other thing that can help, if the engine is in the vehicle and the clutch is connected - simply step on the clutch pedal while someone else shoves the transmission home. If - the hang up is a minor misalignment in the clutch, this will cause it to float and the trans will slip right in.

[Captainfab]

The first thing that comes to mind for me is the throwout bearing hanging up. Did you lubricate the front bearing retainer where the TO bearing slides? Did you test fit it prior to installing the trans? If you have changed the clutch as well, do you possibly have the tall TO bearing and really need the short one? Couple things to check.....

[LILRED66]

Good info guys. Thanks for sharing.

[2tons of fun]

obvious but did you center the clutch disc before you tightend the preasure plate?

did you leave the tranny in gear so you can twist the out ptu to line up the splines for the disc?

[SBC RACING]

Thanks for the tips guys, i'll let you know how it goes..

[Sicboy]

Markeb01 is dead on. I just re-installed my rebuilt saginaw and I fought with it for nearly two hours. Then someone suggested using bolts for guides. 15 minutes later, the tranny was in. Unfortunately, I have to pull the SOB back out as it is grinding when downshifting from 3rd to 2nd. ;( Also, if you're using a needle bearing pilot bushing, it has very close tolerances.

[derider]

Originally Posted by markeb01

One thing I've found that helps is to come up with 4 long bolts the same thread size as the transmission to bellhousing bolts. They should be the same length as the pilot shaft, if there's enough room in the vehicle to use them, or as long as possible. Cut the heads off and cut a slot in the end so they can be installed in the bellhousing with a large screwdriver. Then slide the transmission over the bolts. It really helps make sure everything is lining up, and prevents bending the clutch plate when your arms get tired or the jack slips.

The other thing that can help, if the engine is in the vehicle and the clutch is connected - simply step on the clutch pedal while someone else shoves the transmission home. If - the hang up is a minor misalignment in the clutch, this will cause it to float and the trans will slip right in.

Diddo, I did this and made a huge difference from the last time I changed out a tranny. The studs and the clutch pedal popped right in!