The Stovebolt Site Forums The Shop Area Driveline Dropping the transmission

4speed. Just began dropping the tranny for the first time today. Went to drain it, to make it lighter, and about a half of a gallon of water came out.

The truck hasn't ran in 15 years until i got the engine working this month.

Couple of questions: How did water get in there?
How do i check to see if anything was damaged by the water?

Wow. I've never done it, but there is a cover on the driver's side of the gear box that you could remove to get a look inside. It's where a pto would attach. I don't know how water could get in there. I worry sometimes about getting water in my axles but not my gear box or transfer case. So I just try not to drive through water.

You can easily pull the side cover on the driver side to check. These are really tough transmissions so if it was sitting on top of the oil you should be able to see how much damage it did. I am guessing after that length of time you may be looking at a rebuild kit, bearings, gaskets, and if badly pitted or broken some internal shafts and gears. SM-420's are common so if it is really bad source a replacement. I have bought and sold good ones for $100-150, which will be significantly cheaper than a rebuild or even parts.

Inside the tranny


I found this in the bottom of it. It's not a tooth. Any idea what it is.

Small part

You need to clean it out to get a better idea of condition. I used Kerosene to clean mine out. I put the cover on filled it up and sloshed it around. Drained an refilled it a couple times. Not sure on the part but I would want to look closely to see if I can spot where it came from.

would gasoline work?

Gasoline would work as a solvent, but it is dangerous.

Kerosene or even diesel fuel would work and they would be a little safer.

Diesel it is. Thanks guys! Getting closer every day.

Plan on replacing any roller , needle and ball bearings as well as their races, the water will have rusted and scored them if it has sat that way for any amount of time. You'll need to take a close look at all the gears as well. This means a complete tear down. Is the truck it is out of a 4x4? Trucks that have done a lot of river crossings commonly have this problem. I bought a truck many years ago now that had a transfer case in the same condition as your transmission.......the PO loved to cross streams with it!

-Mike-

Using gasoline as a cleaner is very dangerous. Gasoline vapors sink to the floor and are difficult to disperse. Any spark can ignite them easily.

Plain old cooking oil works pretty well as a solvent and its not dangerous. When we got rid of our Safety-Kleen parts washer, they notified the Texas Environmental Commission which they routinely do to retaliate against former customers. When the TECQ found we were using Crisco cooking oil, they couldn't think of any regulation we were violating. We even use it to spray trailers before we load pre-mix paving materials so they don't stick. It makes the trailer smell like a hamburger, but thats ok.

Need a machine shop in Houston to turn the flywheel. Any one know of a good one.

How about a pressure washer.
It already had water in it.
Taker her to a do it yourself car wash.

Don't forget the wax cycle. It will lube her up.

You could just buy a used tranny.
Here is a link to hundreds of junk yards data bases and what they have in inventory.
www.car-part.com

In the 2nd field select:
Chevy Truck-10 Series (1987 Down)

Next page input range 47-55,
I not sure what years Chevy used the same 4 speed tranny. I am pretty sure they used them from 47-55.

This is what you should end up with.
Link for 47-55 transmissions

Hope this helps,

The piece pictured looks like a piece of a broken syncronizer key.

Will the transmission work with that piece broken?

It may prevent you from shifting into third or fourth(which ever one is broken)if the other piece left binds, or it may clash shifting into that gear.