The Stovebolt Site Forums The Shop Area Driveline Getting Ready To Pull my Sm420

Getting ready to pull the transmission out of my 55’ 3800.

Been poking around the service manual and the forums but figured I’d post here.

Any lessons learned? Any I wish I knew or hindsight is 20/20?

Planning to take my seat out and use an engine hoist to lift up and out through the cab. Pulling transmission only not planning on clutch.

I was pit crew for a project like that. Executed as you suggest. I was the guy under the truck sacrificing my ribs as we jockeyed the sm420 around. But it came out pretty easy. Going back in was a bit trickier. Done same way in reverse.

Making pilot bolts with no heads helps slipping out. Also works to put rope across shoulders to take weight off, then use hands to manipulate fasteners, etc., if working alone.



Ed

If on concrete floor, not gravel etc. A motorcycle jack will work wonders. And strap it to the jack. Trust me. Ha. Very low profile, wide, stable, and saves your back and ribs. Raises up and down. On wheels to boot. No to mention if you cant find 1 to borrow. Consider the $100 well spent. Even if you don't have a motorcycle, itll come in handy. Rear ends, etc. Even wheeling heavy stuff around the garage.
Oh another thing is that when going back in, once started, i usually lay on my back behind trans and push with my feet. It may sound wierd, but leverage is hard to come by pushing 135 lbs. And as you push, its easy to wiggle atad bit up and down. Good luck.
And 1 more thing. If your pulling the trans, look at the clutch. I had to do mine 2 months after a trans only fix in a towtruck because the clutch failed and it felt good at the time. Its not that much more work since you're already there.

The pilot bolts Ed mentioned are essential. The one on the passenger side has to clear a bump in the case. It was one of those cut a bit off, test fit, cut a bit more off and repeat until you can get to fit jobs.

Make sure you have someone there to help in case something goes wrong. I bought a adaptor to turn a floor jack into a transmission jack. The guy who sold it to me told that he had a transmission fall on him and he was pinned to the floor for 2 hours. Finally, his wife came home and helped free him. Fortunately, he wasn't hurt, he was just stuck. The SM420 is tall with a rounded bottom - it does not want to stay upright. Probably not a issue if you, as you say, are going up into the cab. However, you will still need someone to help guide it out of the cab.

The first time I did it, the cab was off. Easy! I wish I had changed the clutch back then.

Rather than pulling the tranny up into the cab with an engine hoist, drop it to the floor. Use a chain attached to a couple of the cover bolts. With it secured, loosen the bolts, go up on top and jockey it out, then drop it down. No one under the truck when it's loose to get hurt. Once it's on the floor, crawl under and drag it out.

Pilot bolts aren't really needed coming out, but going back in, are nearly essential.

Thanks Guys

Edpruss and Klhansen what do you mean by pilot bolts?

Using the top cover bolts is exactly how i was going to rig it. I was going to pull it up into the cab but I like the motorcycle lift idea and dropping it down as I have bikes.

My understanding is once disconnected from drive line, rigged and unbolted it should just slide back out of the bellhousing (I'm sure with some persuasion). Correct?

What they are referring to you might call studs but only threaded on one end. Usually take a bolt same size as the attachment bolts that is longer and has additional non threaded length beneath the shoulder. Cut the head of the bolt off, determine the length needed and then round off the smooth end with a grinder ....
These pilot bolts , usually use two , they help guide the transmission into the bellhousing and orient the trans so the bolts start easier.

I have dropped them out the bottom with a helper, and a regular floor jack. Helper held onto the shifter just to keep it upright so it would not tip and fall off the floor jack. I have since bought a floor jack from Harbor Freight and it seems to work ok, just a bit short for use on my 58 2 ton.

Yes for lowering the gearbox down to the ground via engine hoist thru cab door and then slide it out from under.

I see, so thread the studs in first so they are sticking out, slide the transmission into place guided by the pins, then swap them out one by one so it’s easy to line/bolt the thing up. I like that idea..

General consensus looks like avoid bringing up through cab drop down to ground... will plan for that.

When I yanked mine it was down to the ground. I was so mad trying to take it with the bellhousing I ended up kicking it out of the hole letting it fall onto boat cushions. Found out later it separates from the bell housing after I scrapped tons of gunk off it.

Another recommendation: read the shop manual first.

... and cut a slot in the smooth end so you can back the pilot bolt out with a flat blade screwdriver.

Put the 2 guides in, install transmission and tighten the two regular bolts. Unscrew the two guides and put in the other two regular bolts.

I ground some wrench flats on my pilot bolts so I can get them out. Screw slots are easier to make, harder on your knuckles to use. Keep in mind that if you use pilot bolts that are too long on the bottom, you won't be able to get them out past the clutch when you're done. Top right must be shorter to clear the case. Top left can be longer.

You will note that two of the bolts are longer than the others. I put the two long bolts in the upper right and lower left holes and use them to draw the trans into the flywheel's pilot bearing hole while pilot studs hold the alignment in the other two holes. Even with an old input shaft it's near impossible to get the clutch lined up exactly with the pilot hole. So the bolts will overcome the drag. Also disengage the clutch to ease the installation when you get that far. That allows the disc to move slightly. Too much grease will get thrown onto the clutch disc, so use sparingly.

A transmission adapter for a floor jack would be a worthy investment as is enlisting your wife or friend to hold the shift lever while you align the holes. Getting the transmission onto the jack once under the truck can be done with a couple of two-foot, two-by-fours across the floor opening and hooking some ratchet straps around them and the transmission and lifting it enough to get the trans onto the jack.

The pilot bolts mentioned are a must, the left side can be longer than the right, you'll see the clearance difference on the case.

Thanks again everyone, now digging into this this all makes a ton of sense.

Took flywheel cover off, removed drive shaft. Coming back to it llater this week with a clutch head bit to remove the transmission cover, disconnect all the brake parts, Speedo drive. Hoping to drop it and install my replacement next weekend.

I see now, you can’t do this job without guide bolts.


Are clutch parts readily available or am I better off having brake and clutch relined? I have the 2 piece friction style brake. I guess this type isn’t typical for the 3800?

Leave trans in direct, easier to rotate by hand, scissors jack on roller skate also works.

Ed

Are you asking about the Dual Shoe Parking Brake? If so, you'll need to have yours relined. I've never found a source for those shoes, I think they went obsolete decades ago...

Mike B

I figured as much for the dual shoe.

After reading looks like I have to measure bolt pattern/diameter of the clutch assembly that’s in the truck to see if I can buy replacements.

These guys can probably help you.

Brake Materials and Parts Inc
800 Sherman Blvd
Fort Wayne, IN 46808

260-426-3331

BrakePartsSTOP@aol.com

www.BrakeMaterialsAnd Parts.webs.com

Scott and Margaret Bethke

When I was a 150 pound high school kid, to remove the SM420 from a 57 3100, I would sit on the seat and pull it loose and lower it down using the shift lever, we didn't even own a floor jack back then, just a chain hoist and a good beam in the garage.
No I could not do that now.