M21 Tranny Install
Thread Starter
Racer
Joined: Nov 2001
Posts: 499
Likes: 4
From: Loxahatchee FL
M21 Tranny Install
I am trying to install the M21 transmission in my 68 BB. The tranny stops going in about an inch from mating with the bellhousing. What am I sticking on, the clutch disk or the pilot bushing? I test fit everthing before reassembly, so I know everything fits.
Thanks,
Rick L.
Thanks,
Rick L.
Thread Starter
Racer
Joined: Nov 2001
Posts: 499
Likes: 4
From: Loxahatchee FL
Thread Starter
Racer
Joined: Nov 2001
Posts: 499
Likes: 4
From: Loxahatchee FL
Oh joy! When I first tried to test fit the clutch disk to the input shaft I thought it was the wrong one, but then discovered that it is a really precise fit. I can't imagine how I am going to be that precise while trying to install the tranny. Should I be doing this with the transmission in gear or in neutral? It's in gear right now.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
What I have done on occasion when this happens it hook up all the clutch linkage. When you have the transmission almost in, have someone push in the clutch. This will release the clutch disc just in case you have not lined it up perfectly. Once the disc is free the trans should slide in very easily. I have done this many times when someone, me included has not lined up the disc and pilot bushing just right. It has to be almost perfect to get it to all go together.
Thread Starter
Racer
Joined: Nov 2001
Posts: 499
Likes: 4
From: Loxahatchee FL
What I have done on occasion when this happens it hook up all the clutch linkage. When you have the transmission almost in, have someone push in the clutch. This will release the clutch disc just in case you have not lined it up perfectly. Once the disc is free the trans should slide in very easily. I have done this many times when someone, me included has not lined up the disc and pilot bushing just right. It has to be almost perfect to get it to all go together.
I pulled the tranny back and slid the alignment tool in and it goes right in all the way and seats in the pilot bushing. I know it is seating because the pilot bushing I put in has a slight lip on the inside, and I can feel that lip with the tool, and then feel it go all the way in.
How about the angle of the engine and transmission? I am doing this on a scissor lift and I have the back of the engine supported so that I can raise and lower it with the lift. Any tips on getting the angle correct?
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Only have some push in the clutch when the transmission is in far enough where the splines are engaged. You are working the trans in and when it has that last inch or so to go have someone push in the clutch. The disc cannot fall out or down if the trans is in this far.
As for the alignment yes try to get the trans and motor on the same plane. I know it is tough when you are wrestling the trans but don't be afraid to give it a little wiggle up and down and side to side.
I also use guide pins to make it easier. Get yourself some long bolts and cut the heads off of them. I use 2 of them. Thread them into the bellhousing and use them as guide pins. Once the trans is "home" thread in the other two bolts just snug so the trans does not go anywhere. Remove the guide pins and put in the other 2 bolts.
I never liked the alignment tools either. They have to much slop. I have always used and old input shaft from a Muncie. The fit is much tighter for alignment.
As for the alignment yes try to get the trans and motor on the same plane. I know it is tough when you are wrestling the trans but don't be afraid to give it a little wiggle up and down and side to side.
I also use guide pins to make it easier. Get yourself some long bolts and cut the heads off of them. I use 2 of them. Thread them into the bellhousing and use them as guide pins. Once the trans is "home" thread in the other two bolts just snug so the trans does not go anywhere. Remove the guide pins and put in the other 2 bolts.
I never liked the alignment tools either. They have to much slop. I have always used and old input shaft from a Muncie. The fit is much tighter for alignment.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Instructor
Joined: May 2010
Posts: 172
Likes: 3
From: Hesperia California
If trying to get someone to help is almost impossable or by the time you find someone to help you could have put the trans in 5 times, this is what i do. Oh by the way guide bolts are a good way to. I get two longer bolts one on top and one on bottom snug them up abought a half turn after snug get in the car push clutch in, then give the bolts a nother turn and repeat this untill the trans is in. No problem Ha Ha, always works for me, Id rather do it myself. Every time i have someone help me it takes twice as long 
Instructor
Joined: Nov 2009
Posts: 123
Likes: 26
From: Tulsa Ok.
4 speed
When i installed my 4 speed it would not go in all the way. the problem was that i did not drive the pilot bushing in all the way and would not allow the trans. to go all the way in. Drove the bushing in all the way and trans. went in just fine.....
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Just put it it any gear. Turn the shifter fork to put it in any gear. If the trans is only an inch away the splines are engaged. They engage pretty quickly. Tightening the bolts to draw it in is risky no matter how you do it. Many have done it with no problems and had success but you would hate to hear a CRACK and break off an ear of the transmission.
Thread Starter
Racer
Joined: Nov 2001
Posts: 499
Likes: 4
From: Loxahatchee FL
Worked on this some more today. I tried everything you all suggested, guide bolts, having someone push in the clutch while I tried to feed the transmission in. Nothing worked. So, I figured it had to be something screwed up inside the bellhousing. I pulled the bellhousing and just for ****s and grins I slid the transmission in to the pressure plate/clutch disk. Guess what, it went right in all the way into the pilot bushing. No problems. So, what in the bellhousing could be keeping the transmission from going in? I am starting to suspect the part that the through-out bearing rides on. Seems like it is kind of a tight fit between the bellhousing and the flange at the transmission. I ran out of energy today, but I think I am going to try putting the tranny in with the bellhousing loose and see if that will work.
Any other suggestions?
Thanks,
Rick L.
Any other suggestions?
Thanks,
Rick L.
Instructor
Joined: Sep 2007
Posts: 198
Likes: 0
From: Colorado Springs Colorado
Are you bolting a new bell housing to the engine? It sounds like your bell housing isn't dialed in to specifications, and needs off-set locating pins. If it's the same bell housing going on the same engine, this probably isn't the problem. If it is a different bell housing, or different engine, do a search here for dialing in a bell housing. Let us know.
Thread Starter
Racer
Joined: Nov 2001
Posts: 499
Likes: 4
From: Loxahatchee FL
Everything is original except for the pilot bushing, the clutch disk and the pressure plate. I am starting to think that maybe a wire for the starter got caught between the bellhousing and the block.
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
Sounds like the throw bearing may not be sliding onto the sleeve. When you hit the 1 inch stop, can you move the arm back and forth? The throw bearing should slide back and forth a bit. If it's not sliding onto the sleeve the arm may not move freely at all.
You may try wiggling the arm up and down just a bit as you insert the transmission, try to get the throw bearing to slip onto the sleeve.
It's been a while since I've seen the input shaft on my transmission but I think there's a
slight taper which should allow a slight misalignment with the pilot bushing. If the bushing were the hang up I think you'd get closer than 1 inch.
You may try wiggling the arm up and down just a bit as you insert the transmission, try to get the throw bearing to slip onto the sleeve.
It's been a while since I've seen the input shaft on my transmission but I think there's a
slight taper which should allow a slight misalignment with the pilot bushing. If the bushing were the hang up I think you'd get closer than 1 inch.
Thread Starter
Racer
Joined: Nov 2001
Posts: 499
Likes: 4
From: Loxahatchee FL
Worked on this some more tonight. Tried getting it to go together with the bellhousing mounted but loose. Still no go. So I stripped it down to the flywheel with the intention of knocking the pilot bushing all the way in, instead of the 1/8" or less it is sticking out. Whacked on the bushing a few times with a socket and hammer and it wouldn't budge, so I figure it's seated. So just for the heck of it, I tried sliding the input shaft into the pilot bushing with nothing else interfering and it WON'T GO IN!!! I know I test fit the bushing on the input shaft before I started putting everything together and I compared it to the one I pulled out. The only difference was the bushing I took out was steel colored and the new bushing is bronze colored. They are both definately bushings and not bearings. I froze the new bushing and tapped it in with a hammer and socket. The alignment tool that came with the clutch kit fits in the bushing just fine.
The clutch set is from Luk model 004-049. I ordered it from AutoZone.
Anybody got any ideas before I rip this bushing out and try another one? Anybody know a bushing that will definately fit a 1968 427/400 that is all original, as far as I know?
Thanks,
Rick L.
The clutch set is from Luk model 004-049. I ordered it from AutoZone.
Anybody got any ideas before I rip this bushing out and try another one? Anybody know a bushing that will definately fit a 1968 427/400 that is all original, as far as I know?
Thanks,
Rick L.