Does anyone have any experience with the old Merc 3 spd OD transmissions? I have an opportunity to buy one (looks okay inside) and understand that they have a 30% overdrive unit. The solenoid is shot on this one but I also understand that you can replace it with a manual mechanism and that would be fine with me. I also understand that they will bolt right up to a 51 8BA flathead with the truck style (full) bellhousing. Were these trannys prone to problems or tender (more so than the truck 3 spds)? My flathead is a 239 and is (well, is in the process anyway) very moderately warmed up with dual carbs, headers and dual exhausts so I doubt that HP would be an issue. Any thoughts or cautions would be appreciated. I'm sure that I'll have to modify / replace the existing crossmember as this tranny is longer than the existing 3 spd but this would let me keep the 3 on the tree (yeah I know but I like it) and yet give me a more relaxed cruise RPM with the 3.92 gearset currently in the rear. Whatcha think?

Leaks

 

From discussions on some Flathead related boards - Parts are difficult to find and you may need to float some loans to purchase.

 

But...as they say...if I could get it for $100 and it looks good (other than the electric solenoid) is it worth pursuing in your opinion? I have a friend who wants me to take some of his old flathead "stuff" (gearbox is amongst the pile) off his hands and he's talking a pretty good deal for the lot. $100 breaks out the gearbox piece as I see it...whatcha think?

Leaks

 

I am currently putting the same unit in my '53. Check the input shafts of your original trans. and the OD unit because the car OD units have a smaller input, shorter by approx. 1" and smaller diameter. My truck bellhousing has the rear frame mounts and my trans. does not have a mount at all. My trans. and OD unit will just hang there. Parts can be found as this OD unit ( borg warner R 10 ) was put in cars from 1938 to 1972 and all the internals are interchangable. There is an R 11 unit that was built in the 60's and up for larger engines but I don't know much about them. Also check the side case of the 3 speed to see if you have the threaded bosses that the clutch pedal shaft plate bolts to. If you have to swap these, be carfull to replace the reverse lock out cam that activates the 1st/reverse shift fork. Without this, a mistake could clean house in the OD unit. For the price you quoted, I think you will have a very nice correct looking OD cruiser. Jeff.

 

I dont have much experience with the Merc. I am curently running a Ford behind my 240 six. From what I understand there is no difference in them. I have not had any problems. The solenoid was shot and I had to get another one to get it to work. I am curently using one out of a 63 and having the original one rebuilt. I understand there are 12v and 6v solenoids out there and that the 12 is more dependable. I have a stock setup with a kickdown swith on the gass pedal. I am thinking about relocating it as it has shifted a couple times when I did not want it to. I was really surprised at the difference it made. I can now cruse comfortably at 70 vs 50-55