anybody know anything about 3 speed transmissions with over drive how they work and would it improve lowering my rpm on the freeway with my new 3.73 rear end gears? thanks robert
Overdrive They work by a planetary gear system and reduce the engine's RPM's by 33 % . I assume you now have an open driveline typ of tranny ? . If so ,just buy a used '55 ~ '62 Chevy light duty truck or passenger car tranny with overdrive and it's pretty much a bolt up deal . Be aware the solenoids are expen$ive when they fail . I see these trannies @ the Long Beach Swap Meet occasionally .
3 speed with OD I'll be interested in how you come out using the 3 speed with OD. I have a Borg-Warner with OD that I am looking at for my 53'. It sure makes a lot of sense and gets rid of the rear-end ratio dilemma. I got a dandy of a deal on a NOS cable. Some concerns I have heard about but I haven't gotten that far in the project are that the original column mount shifter is the easiest application. The floor shift set-up has interior seat clearance issues. It also has some issues with bracket clearance and the OD solinoid. Bracket manipulation can be frustrating but rewarding. There was a company in the south, name escapes me at the moment (moonie/charlies's)that made shifter's for these in the 60's and other after market goodies. They are still in business, I never got an email response from them about the shifter existence. I hope this works out, cause I'd love to just bolt that tranny in. Evan and some other's have done this with success
What speeds and RPMs are you doing with the 3.73 gears. I want 3:73s and have the 3.73 rear on a v8. It got plenty of acceleration and speed. Dont have a tach on it but went faster than the speeo reads but was only doing 80% of what it read. Broke a rod cap so I guess it was abont redline. To my thinking a 3.73 would be perfect for cruzing with the 235 but have not tried it?
Cruising Speeds Yes the 3.73 ratio favored by American manufacturers for automatic equipped vehicles is well nigh *perfect* for an InLiner with stock tranny and original diameter tires ~ . As soon as you go to 14" or low profile tires , you'll need some help and the overdrive will be the answer , as long as you understand it's proper operation and limitations . You cannot and MUST NOT back up in overdrive else you'll break the sun gears's ring . I like to by pass the governor so OD can be engauged in 2Nd. gear for climbing hills easily . OD gives you a higher cruising speed but in use it actually slows you down going up through the gears...
Your 3.73 gear will be pretty shallow gearing in overdrive. I always thought an old Borgwarner was a 30% but Nate says 33% so I won't argue there. Anyway, your final drive will be between 2.50 (33%) or 2.61 (30%). I think the old 235 can pull that but a heavy load or trailer toting would be better locked out of OD. Take heed of the solenoid advice, I have seen whole trans/OD units for $125-$150 at swap meets and solenoids alone for a $250 asking price. Many will have 6v solenoids but wired right they have never given me a problem. The hey day was in the fifties so from the mid-decade on they are 12v. Much harder to find are the 1965 up units with the fully synchronized tranny and the fine splined output shaft. Found mostly in pickups the ones in the 67-72's with the heavy duty three speeds will actually tolerate abuse from hauling or mild racing. I latch onto any I find because even though the housings vary the guts from all interchange for years be it for a Nash, Studebaker, Willy's, you name it.
Oops That reminded me : I was looking at a late 1950's vintage Borg Warner gearbox with overdrive but the input shaft looked funny and had very fine splines , my buddy the junkman told me it was from a Studebaker so no one wanted it in spite of the 12 volt solenoid and so on.... IIRC he wanted $45.0 for it.....
