The Stovebolt Site Forums The Shop Area Driveline Update: SM420 won't slide the last 1/2 inch during install

My 4-speed is hanging on a long guide pin (upper left) and the splined shaft through the clutch hole and into the crank. I can't get it to slide the last 1/2 inch. I giggle it and push it to no avail. I've pushed with my feet but no luck. I'm a little leery about getting a longer bolt to draw it in by screwing in the bolt.

What can keep the transmission from sliding flush with the bell housing once it's been started?

Thanks.

Pilot bearing/bushing. The snout of your transmission is not going into the center hole.

Would turning the flywheel 90 or 180 maybe find a sweet spot?

Can’t hurt.

Possibly the wrong pilot bearing? Wiggle giggle and foot pushing usually gets the job done..... Maybe double check b4 wasting more time and effort?
Another thought would be splines on the input shaft buggered up, not sliding through clutch disc?
Or wrong clutch or installed wrong?
Put trans in gear and turn output shaft as you push?
Something just dont sound right.....

What did you change? Clutch? Transmission? Flywheel? Pilot bearing? Throw out bearing?

If you only have one guide pin, the input shaft may be below where it needs to be because of gravity. I would recommend trying a 2nd guide pin, that's assuming you have the clutch disk aligned properly. Did you use an alignment tool when you installed the clutch disk and pressure plate?

Like Glenn said, in gear, high works best, so someone can turn it as you push!

Ed

If the clutch disc wasn't aligned properly the input shaft won't align with the pilot bearing. Have somebody push the clutch peddle in while you try and wiggle and jiggle the tranny in the last 1/2 inch. "DO NOT" try and tighten the tranny bolts to draw the tranny in.

Agree with all the advice. As Kevin said, it takes two guide pins, not one and the shaft. It also takes the trans to be slung from above sometimes. Hanging on a chain so that X. Y and Z are all floating. A jack under can help that somewhat. A cherry picker thru one door will do the trick if all the parts are correct and installed properly. If you can get two long bolts started, they will be guide pins. (but not to carry load). Remove the two long bolts after two proper bolts are in.
The input shaft nose to pilot bearing I.D. is a pretty tight fit which needs a "straight in" install. The nose is on the end of a 125 lb cast iron chunk. It is about a 1/2 inch engagement.

Was this transmission mated to the engine previously?

I also ran into this situation installing my SM420. Sometimes the plastic clutch alignment tools are a bit off. 55shaker's advice is right on the mark. I had my wife push the clutch in while was pushing with my feet from below. The transmission went right into place. I also obtained an old input shaft to use as a clutch alignment tool.

Good luck,

I keep an old input shaft around, too, just for that reason.ED

The afore-mentioned are probably your best bets. My experience with mating an 3 speed OD trans into a chevy 348 on my 1957 pickup was exactly the same. I couldn't get the trans in the last 1/2 - 3/4 inch. In my case I found out that there was a short throwout bearing and a long one (if I remember correctly the stock one was the long one). The differentiating factor was that my clutch was a competiton clutch and pressure plate, not stock. The short throwout bearing solved it. If nothing else works, it is something else to investigate.
don

Wally/Montana did you ever get that tranny installed???

Start the upper right bolt loosely into the bell housing but don't apply any pressure to the trans case. Push the clutch pedal down to free up the disc. The trans input shaft and the pilot bushing will align and the trans will slip into place.
Jerry

(To paraphrase some ancient, sorry for such a long post. I didn’t have time to write a short one.)

Thanks to all for your great advice. I'm back with my ‘48 but still in a bit of a funk about my transmission.

Background: 17 years ago, I installed my old SM420 on my “new” 261. I used a great tranny lift (no longer available) which had very smooth pitch-yaw-roll adjustments. It took about 3 min to get it bolted up but I was a young 60-year-old then.

Current: Last Spring, I reinstalled the 261 after some work on it. I used the splined plastic alignment tool for the clutch. I started and ran the 261 to replace the assembly lube with real oil. I kept the alignment tool inserted during this in case the clutch decided to wander a bit. I then left town for a few months.

Upon returning, I rented a tranny lift which was a little floppy and couldn’t clamp onto the tranny very firmly. I used only one long guide pin on the left side of the bell housing and the input shaft for aiming the SM420. As noted by lots of you, I needed another guide pin. The end of the input shaft was not getting into the pilot bushing.

I slid the tranny back and the plastic alignment tool still fit into the pilot bearing. The clutch seemed to be aligned properly.

I'm guessing the input shaft might have been tipped up or down (or back or forth) and my giggling of the tranny didn't solve the problem.

To Do Now: 1. I'm going to realign the clutch to make sure. I bought one of those clutch alignment kits that had an un-splined metal cone-like thing that presses into the clutch "hole." It seems like you need more than 2 hands to make this work. Do they really work? I've also got a new plastic splined tool.

2. To press the clutch during the last push as suggested, do you install the clutch fork on the throw out bearing even though the transmission isn't all the way in there?

3. I’m going to give the rental lift another chance with 2 guide pins. See pic. One must be fairly short because a longer one will not be removable due to a lump cast in the tranny.

4. Any other advice? Thanks again.

Clutch fork should be installed before the tranny is installed. Never had much luck with the plastic alignment tool. Always used an input shaft taken from an old transmission.

It's all coming back. No,, not really.

So, last time, I put the clutch fork in there and pulled it back to the left? Then, installed the transmission? Then, mated the clutch fork with the throwout bearing and popped the fork into the retaining ball?

If so, at what point would I have Mrs. Wally press on the clutch pedal if necessary?

I was supposed to do all this only once!

Thanks.

The clutch fork and TO bearing need to be fully assembled before stabbing the trans. Most bell housings don't allow enough wiggle room to insert the fork once the trans is in place. Get a couple of trans to bell housing bolts installed loosely, then push the clutch pedal down and shove the trans into place. On a big heavy trans I've also used a come-along or big bungee cords to make the trans and bell housing mate up.
Jerry

I wish I had read something like that a couple of years ago, When reinstalling my SM420 into my 3100 I thought it would be easier to install the fork after the trans was in place since it is a bit of a struggle doing this by myself. Got the trans fully in place then spent a couple of frustrating hours trying every which way to get the fork in place. I even unscrewed the ball mount thinking I could thread it back into place once the fork was close. No joy. Had to pull the trans and start over.

All great advice. And yes, clutch fork snapped onto the ball stud, throwout bearing on the fork, clutch aligned/centered, transmission in gear so you can turn the rear yoke/output shaft, and you should be able to wrestle that thing in there. Is there any debris/rust build-up on the bearing retainer, or the hole in the bellhousing for the bearing retainer? That may also cause it to hang up.

Thanks! My purpose in asking questions is to make everyone else feel like Einstein.

Finally smiling BIG. Mrs. Wally says I look like Professor Irwin Corey. Don't know if it's because of my face or hair.

I was ready to punt and store for the winter. I had rented a tranny lift 3 times. Then I supported the tranny using a come along on a 4x4. The left end of the 4x4 was on the steering column which worked OK.

The 2 guide pins were engaged and the clutch disc was already aligned. I suspended the tail of the tranny with the come along. I jiggled, lifted and wobbled it while Mrs. Wally pushed in the clutch pedal. No luck.

Then I measured the distance between the mating surfaces at the upper pins. 1". The distance between the mating surfaces at the lower bolt holes was about 1 1/2". Hummm. The rear of the tranny needed to drop to make the mating surfaces parallel.

I did that and pushed, jiggled and wobbled it. BINGO. Here came my Irwin Corey look!!

I had usually looked to see if the transmission was level or so but realizing the mating surfaces had to be parallel was the key that stupid me had overlooked.

Picture: I could not make the long pin budge for removal after the 1st 3 bolts were installed. Oh, no. Another problem. Well, I had attached a chain for possible use with the come along. One of the bolts thorough the chain link had bound against the long guide pin. This only took 10 minutes to solve.

Thanks, thanks, thanks everyone!

Congratulations

OH NO! The dreaded too long bolt!

Glad you got it installed.

When I started twisting wrenches & would be losing my a## on a job an older guy would ask "you want know flat rate time on that job?".
Glad you got it whipped!

Nothing like getting paid half of the flat rate (the shop got the other half!) and not a penny more to make a wrench jockey get very creative with his approach to a job. That was particularly true when the shop labor charge was less than $10.00 per hour! ("Minimum wage" was 90 cents!) A flat rate mechanic provided his own hand tools, did not have any "benefits", and was expected to beat the flat rate manual time whenever possible. It was not uncommon for a good man to book 50 or more hours of time in a 40 hour week. Most mechanics in the 1950's were considered to be "contract labor" and thus were responsible for paying their own income taxes- - - -no deductions by their employer with the exception of Social Security, and sometimes not even that!
Jerry

My sm420 case has bulges that prevent me from using alignment pins. I have used long bolts and removed them after the bottom ones are in place. With every decade that passes this job gets harder. The last time, a year ago last summer it took another guy even older than me pushing with his feet on the u-joint flange while I operated the floor jack. It took about 10 minutes of blue-streak words and huffing till it was in.
I too once worked in a flat-rate shop. Paid half of shop rate and eat your comebacks. First place the trucks I worked on went to was the steam-clean rack. I had to eat that time but it paid off in the end. Time on anything that came from the rust belt was negotiable. I made frequent use of the nut splitter and a rosebud on the torch. Now I don't drive any rig I have to work on in the winter.

Pushing on the U-joint will be made easier if the trans is in high gear and the U-joint is twisted while pushing!

Ed

Yes. That extrusion of cast iron blocks the use of a long guide pin on the upper right side. I used a short pin there as shown in the first picture.

The extrusion on the transmission has a threaded hole also seen in the picture. It must be the pivot point for a hand parking brake found in some (all?) of the larger trucks. 2nd pic.