The Stovebolt Site Forums The Shop Area Driveline sm 420 top

so, i'm working on a sm 420. i had the trans out and took the top off to have a look to see if i could find any remnants of a plastic top that had fallen into the trans...long story.

i also removed the pto. in an effort to reach the plastic pieces, i moved the trans around without the top on and some of the gears moved around in the trans. now with the trans installed, when i line the shift forks up and replace the cover, the trans wont go into gear.

what have i done that has caused this to happen and how can i correct it?
thanks

Make sure the 3-4 slider is in the middle so you see both 3rd and 4th syncros, then make sure the first gear slider is 4-3/8" outside of yoke slider to outside of yoke slider, line up the reverse arm to fit in the top cover and you are golden. Check the top loader cover to make sure the 1-2 yoke is in the middle detent of travel and the three four yoke is in the middle detent, if they are the outside of 1-2 yoke to outside of three four yoke is 4-3/8"

hey, i think thats just what i needed!

thanks, i'll let ya know how it works out.

well, that didn't do it. now all i can get is reverse. when the motor is running, all i get is grinding and nothing else.
any suggestions?

send me a picture of your top loader inverted and the gear box with the top loader off.
sstock6264@comcast.net

with the top off, you need to make sure all the shifting forks in the top is in neutral and also the transmission. 1-2 and 3-4 should not be a big problem, reverse in the trans can slip fairly easily and you need to watch that one as you put the top on.

Yes pretty sure Mike he has the trans in two gears at once.
I wish I could find a picture to show him, but if he first flips his shifter top over he will see the 3-4 shift yoke which is the smaller yoke, there are three positions for this yoke , make sure it is in the middle detent, now you may not be able to move this yoke if the 1-2 yoke is in any other position other than its middle position, if thats the case move the 1-2 yoke to the middle position first then the 3-4 to its middle detent.

Once the shifter top is adjusted then move to the gear box and make sure the 3-4 slider is in the middle thus exposing both the 3rd and 4th syncro (see this picture attached), then adjust the first gear by sliding it along the main shaft so the dimension is 4-3/8" between the outside of the 3-4 slider groove to the outside of the slider groove on the first gear.

Drop the shifter top on the gear box making sure the reverse lever slides into the head of the shifter top.

This is one of those things that is hard to explain but really easy to do.

ok, haven't been able to mess with it today but, i'm on it tomorrow.

one thing i didn't say was that i replaced the clutch and have never done one before. i think i did it correctly but is there a chance it could be clutch related?

thanks

Yes of course, especially if you got the disc in backwards

I put a clutch disc in backwards once on an old Mazda years ago..what a terrible grinding sound. I had to pull the disc and replace it. It ground the springs right down and I didn’t trust the disc after that. If that engine is running and you get lots of constant grinding... I second sstock’s suggestion. I’d check the clutch to be sure. PITA but you’ll rest easier.

What did you do with the pto? Did you reinstall it? Put on a cover? Could something be touching in this area?

My 420 top install went very smoothly. It seemed to me that it would only go together if you had it in the right position. Keep trying and asking questions. You’ll get it.

ok guys so here is what i've done so far. after trying to get the the top on for about 5 trys, i realized that the forks on the top were too far back to get it on so, i was able to shift the gear shift arm with the top off. once i did that the top went on but the problem still persists. i' gonna remove the drive shaft, take the top off again and see if i can get the trans in neutral and try again. so with the drive shaft out, i should be able to turn the gears right?
if i'm understanding this correctly, i'm really just trying to get the thing in neutral because thats the way it needs to go together. is that right?

Doob,

This is not meant to belittle you but you really have to read and understand everything that has been written, you are asking questions that have already been covered.
You have to make sure the gear box is in neutral and the top loader yokes are in neutral too. Reread and look at the pictures my friend. Removing the driveshaft is not needed and a waste of time.

ok, thanks for the info. don't worry about belittling me, i'm new at this and getting close to the end of this project and i'm a bit excited. i'll take a breath and reread the answers and go from there.

besides you just saved me taking out the driveshaft!

thanks.

so i just reread your last post and pic. i think i've got the top correct. if i get my trans to look like your pic, and the top is right, it should be good?

Don’t try shifting with the engine running until you get the transmission to shift into all gears w/o the engine running. Once everything is lined up properly as has been outlined in previous posts you should be able to shift every gear without using the clutch and w/o the engine running. Step back take a deep breath then try again.

ok, so i think i have the top on correctly. if it's not than i know i'm wrong before i start but, i've put this darn thing on so many times i'm gettin pretty good. with the shifter in neutral, and the forks and sliders (?) in place at 4 3/8ths apart, i can almost see them go down all the way. i also have reverse so i think its right. without the engine running, i've got 1st and reverse. if i reach down and move the old e brake drum which is disconnected because the rear was swapped to a 1955, , i can get a little bit more movement into 2nd, 3rd, and 4th but then 1st is difficult. the drive shaft is still connected.

anyone know a good tranny guy in tucson? i'm almost ready to toss in the towel.

ok just looking at the pics and have a question. how do hoy move the 3-4 slider back towards the rear of the trans? i have been moving the 1-2 slider to the front.

So your 3-4 does not look like the one in the picture in my above post? You should be able to see both brass synchros when it is in the center detent if not, move the slider back with your two thumbs, it takes a good bit of pressure but can be done.

ok, i got mine looking just like your pic. it seems to go through the gears fine until i start it, then just grinding. when i put the clutch in, i did have a bit of a concern when bolting it together. the pressure plate didn't bottom out. the bolts were pretty tight but there was still a gap. should it sit flat?

when i installed the trans, the last 1/4 inch needed to be pulled in with the bolts but nothing like i had to force it. what do you think?

really, i can't thank you guys all enough and a big thanks to sstock for having the patience to help me out.

Well, now you get to redo the clutch. When you get it all back apart you will see (probably) where the problem is. Before you put it back together get back with us for help. Frustrating but you’ve got this. 🛠

Makes me wonder if you have the clutch disc in backwards, if that is the case, you will be bottoming the clutch disc springs on the heads of the flywheel bolts and probably if that is the case the clutch disc should be thrown away. When you get it apart look at each side of the disc, it will have a label that tells you flywheel side.

Also, if you have a digital camera, snap a couple pics and upload them up by using the full editor, Stovebolt recently had an upgrade and this is a really nice feature, a picture tells the story of 1000 words can't.

Steve

argg.... there is nothing more rewarding then working on your own car....except maybe doing your own dental work!

thanks.

its coming out today

Check the pilot bushing in the rear of the crankshaft while you have it apart and make sure you use the clutch alignment tool too on the disc as you install the pressure plate.

not sure if i posted this already but, i took the clutch and pp out. it was new but not installed when i bought the truck.

comparing it to the old one that i happen to have, they are not the same. the old one sits higher when set flat and the springs/splines flange on the pp are not set the same way.
i've ordered a new set from my local parts place. i'm gonna take the other 2 down and compare them. i'll post an update.
thanks again.

oh, the pilot bushing was replaced when the motor was rebuilt. it looks new too.

ok so... thanks to all the folks on this forum because after many problems and countless questions, i've just driven the old panel out of the shop and around the block. although the thing was running with open hedders and i didn't have the floor pan installed over the trans, it was the best ride i've had in a very long time!

i'm not finished yet and i don't want this to sound like an acceptance speech. i just wanted to say thanks to all the folks who helped.

so, thanks.

I can see your smile.

Keep at it.

Great news, but you must share the solution to the problem. That is how we build a complete data base here at the Stovebolt to hopefully help some other Stovebolter in the future.
Steve

the solution to the top problem was solved using your photos and suggestions. it took some time to get it right but once i had everything lined up as per your pics sstock, the top went right on.

the clutch problem was simple although it took about 5 days and ordering a few different clutches before i figured it out. the motor is a '57, the rear, a '55 and the trans a late model sm420. the problem was the flywheel was a '51, not a '57 like i thought, which i can only guess came off the original 216. it uses a 91/4" clutch and PP so the clutchs were all the incorrect size even though the part numbers were correct, the info i was giving was not. there was also the matter of torquing the bolts down to specs which, i guess is "important"....who would have guessed.

truth is i screwed up the installation from the get go. thanks to all the fine folks here, i was able to correct my errors and get it going. this is a GREAT forum!