1936 Desoto 3 speed overdrive transmission

[Graham Man]

I picked up a 1936 Desoto overdrive transmission last winter. It was removed for a hot rod project about 1978 (don't get me started) anyway it sat in a garage all these years. I am able to turn the trans over from the drive shaft, but it will not shift, it is still connected to the 36 engine. I removed the top mounted shifter, other than a little moisture the gears looked clean. I filled the rest of the transmission up with used 15-40 oil (wanted to get any moisture away from the gears) and it is just sitting. My question is where do I go next? It is a R7 completely centrifugal force overdrive unit with the 3 speed.

[JACK M]

You will not have much trouble getting a good price for this item. The last one I had went right away.

[Spinneyhill]

Get that used engine oil out of it pronto. Used oil contains acids and moisture that will not help keep it in good condition. It is also very bad for your skin.

You should dismantle for inspection. Expect the planetary gears in the overdrive to be worn, or at least their bearings. The gearbox might be OK, but the overdrive is a different kettle of fish altogether. The sun gear carrier is bronze and probably has worn a bit too. And make sure the freewheeling unit inside is bolted on properly.

It probably won't shift coz things don't line up properly and you need to turn the input shaft to help that happen.

[Graham Man]

I put in 15-40 oil with less than 200 miles on it. The transmission spins extremely quiet from the drive shaft side, when I had the shifter off all the gears were spinning freely. When I spin it and try to pull it into gear the drive shaft stops but it will not fall into gear. I did not want to force it. I have not split the transmission from the engine. Is this transmission complicated enough I should find someone who knows what they are doing? I do not want to damage it.

[Spinneyhill]

OK, I take it back about the oil.

These gearboxes are pretty simple. If you have a shop manual, tackle it. Else, get a manual and then have a look. You can't really damage it. Don't force anything. Take photos of each step so you can see where things go back. I do this with clocks. I made one mistake with mine (I hope) by leaving out a little C washer that is poorly shown and called up in the parts book diagrams and shop manuals. The result is it needs to come out again to fit that washer and check the clearances around it. Getting it out and back in is a proper PITA.

Based on my experience, having been sold a gearbox in "good condition" (and at that price!) that looked good in the top but turned out to be a real mess, I would check it before putting it in your car. It is a pain fitting and removing them from the car, so check it out first and make sure it is good before showing it to the car. You will also know it is good and be able to drive it without worrying about it.