transmission help


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By lawdogg1 - 13 Years Ago
Hi there. I have a 56 f100 with the stock 272 with the stock 3 speed manual transmission. I want to replace the tranny with an automatic either an original automatic ( which I hear are very hard to find) or a newer auto transmission. I want something that will bolt up with no alterations or very minimum alterations. My reason for doing so is because when I drive at about 40mph in 3rd gear it sounds as if im revving out already. Wil a 4 spd or auto change this or is it something that I need to change the gears out or both? but either way in the long run i would like an auto tranny. thanks guys any help would be great
By Riz - 13 Years Ago
I Got a Bendtsen adapter for the th 350 for my 292. I was going to get the Mummert for the c4/AOD, but got the rebuilt TH 350 for free so I am more bargain centered than a purist. It also it set up to work without a kick down cable-- it also will adapt the 700r4. It bolts up pretty easy and fabricating the cross member was pretty easy. Comes with adapter plate starter and shims and flex plate etc. I converted the old anti rotation mounts by converting them into struts and bolting to the ears. Only a lokar shifter was additional. The only thing I could not do in the garage was shorten and balance the drive shaft.

Good luck.
By paul2748 - 13 Years Ago
The only way you are going to get rid of the "revving up" is to get a higher (numerically lower) rear gear. All transmissions, except for overdrives, are 1 to 1 in high gear. If you do lower speed driving, a overdrive (o/d) trans isn't going to do you much good as it won't go into o/d. Over 35-40 is when overdrives usually kick in on automatics. A manual o/d, such as a 5 speed will help. Everything you do, except for a stock manual or automatic trans, will not just bolt up. You will need an adapter kit. If you use a factory o/d, then there is a matter of the electrics, drive shaft. The later rears from F100's (9inch) have a good selection of rear gears available.



C-4's and TH350's are not o/d trans. The AOD's are the best bet for an overdrive.



lawdogg1 (1/31/2012)
Hi there. I have a 56 f100 with the stock 272 with the stock 3 speed manual transmission. I want to replace the tranny with an automatic either an original automatic ( which I hear are very hard to find) or a newer auto transmission. I want something that will bolt up with no alterations or very minimum alterations. My reason for doing so is because when I drive at about 40mph in 3rd gear it sounds as if im revving out already. Wil a 4 spd or auto change this or is it something that I need to change the gears out or both? but either way in the long run i would like an auto tranny. thanks guys any help would be great
By Riz - 13 Years Ago
That is correct that the c4 and th350 are 3 speed trans without OD, however most adapters will also accept the AOD and 700r4 that are, mine will also bolt on the 700r4 with no other mods or a 5 speed with just a new flywheel.

The only real reason for me to go to the AT was at the wife's request. It was a small sacrifice to have her endorse the rest of the money pits in the garageBigGrin



My truck has a 292 with 3:89 rear end and 27" tires and I am normally turning about 2800 rpm at 70 mph or so. It seems pretty unusual that your truck would be screaming at 40.



I would first figure out what rear gear ratio you have. You may have some stump pulling short gear that even adding an OD you may end up with it screaming at 55 instead.



If it is just the gears winding out too quick, taller tires are easy and can drop you a few hundred rpm. Next would be the rear gear.



The mods for an AT we're as I mentioned pretty simple, not much welding or fab work--but I did make the mistake of not really thinking through some future mods and ended up reworking some stuff later. But that is what makes it a hobby, what fun is finishing?