My '55 Merc has a 1960 352 with a 4 spd OD top loader from an early '70s Ford truck and 9" rear with 3.31 gears according to a PO. One of my many plans this winter for this baby, and it is third on the list so it may be next winter, but I would love to $hit C@n the OD. I've put almost 5k miles since I bought it in May and used 4th gear for maybe one mile of that. 1st and 2nd gear rips but I go from 5k rpm in second to like 1k rpm in 3rd. That might not be exactly accurate but that's what it feels like. Total buzzkill going from 2nd to 3rd. So I want 1:1 in 4th and a pretty uniform rpm drop between gears. I am very mechanical but not familiar with these trannys. Is there such a thing as changing gears (which I'd be comfortable doing) in the current tranny or should I buy a different tranny? And if so which one? Thanks for any help!
They made more than one version of those IIRC. I had one with a 3.21 or so first and a .8 o/d. Didn't like it either. But until you know what you've got you don't know the effect of the change. With a 3.31 rear end and a 2.5? 1st you might not like that either. See if you can find some numbers so someone more knowledgeable (and they're on here) can tell you what you've got.
Sounds like you have a "3+1" Ford T170F. I ran one in my '39 Ford pickup behind a 289 and loved it. You have to drive them like you would use a 3 speed...and use 4th for just highway cruising. Ford lists the ratios as 3.29, 1.84, 1.00, & 0.69.
Bit more info on what you might have. There's more info out there. http://hermtheoverdriveguy.com/overdrive-transmissions-for-d-18-d-20-and-d-300-tf-cases/2940-2
Good info has been given! Like said you might need lower gears. Your transmission is 1 to 1 in third gear, now. The forth gear is only for the high way. Ive got one in a heavy pick up,with a 300 six, not sure of the rear end, but it’s high (4 th) until at least 65 mph, but then I m good to 80 and that 300 Ford six would get 20 mph on the highway! And we drove it many times to Ft. Hood , Texas from Muskogee, Ok at 80 many times! Loved that truck and transmission, engine, rear end combo! But it was a highway rig! Edit: if you want to change the gears in that transmission, you would be better off selling it and buying a regular top loader four speed. By the way, both those transmissions are very similar in appearance! Bones
If you have the cast iron case with the bulge in the side, a standard 4 speed top loader gear set will fit in.
About fifteen years ago I did the opposite of what you want to do, I put an overdrive gearset in a regular toploader case. It's not a simple bolt in setup however, I had to make up a couple spacers, relieve the case in one spot and a couple other little things I forget now. But then my overdrive gearset was from a SROD, maybe the set from a cast iron overdrive fits right in. Yes, the drop between second and third gears is rather huge.
Thank you very much for all the replies! I will look for numbers on it and post what it is. I'd be happy if 4th was 1:1 and 3rd was halfway between my current 2nd and a 1:1 4th. First real snow of the year up here in NH. Very late for our first snow but that means no more driving the Merc until the salt is washed off the roads probably sometime in May. I'll get back to you on what I have for a tranny. Thank you!
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