I recently bought a very nice 49 pickup (Mercury M68) that I want to be able to drive on a semi-regular basis. The existing transmission & rear-end work, but a top speed of 45 isn't going to make it very useful around here and that's about what it can wind itself up to, and the clashing of gears is a little more than I'm into. I've been talking with a local shop here that is recommending a swap to something like a mid-80's Ranger transmission & rear-end - initially I'm wondering if anyone has done that (or something close) and would have some thoughts. Wondering what the big issues might be.

 

OK, M68 is the Canadian 1 ton (F3), just to clarify what truck we are talking about. It should have the Ford 239 flathead in it, so you need a transmission to mate to it. Unless you install a transmission with n overdrive, the final gearing will be the same as what you have now, 1:00 (direct). I don't believe that you will find an 80's ranger transmission that could be mated to the flathead without extensive fabrication and modification, if at all. And truthfully, none of them would be up to the task.
If you want an overdrive transmission, the best choices are Ford AOD or GM 700R4,(automatics) or the T5 (preferably out of an S10), there are adapters available for these.

As for the rear end, I believe you should have a Timken with 4:56 gears, I know that Chuck's Trucks in CT does have 4:11 gears to fit your rearend, but a more common solution to your road speed issue is a rear axle swap. A '67 to '72 F-250 Dana 60 is a common swap. This is also a solution to your 17" widow maker wheel problem.
I would stay completely away from the ranger rear end as they are not up to the task of a 1 ton.

 

Thanks Joe for the quick feedback - You are right about the 1-ton and the flathead 8 - occasionally it gets referenced a 3/4 ton but I'm pretty sure it's the same vehicle.

Definitely want to stay with standard if possible so the T5 looks like an option, and the rear-axle swap makes sense for many reasons. I'll start looking for the T5 adapters to learn about that , and I'm going to have to learn about Dana rear end options. Lots of fun.

 

Speedway sells the T5 to flathead V8 adapter parts. Free Shipping @ Speedway Motors, The Racing and Rodding Specialists.
For use in a 1T you want to be sure to source a "world class" (google) T5 rather than the light duty T5 used behind I4 and V6s.

 

With an M68 you should have the deeper crossmember (a picture would confirm) that would allow many modern trannies to fit without cutting and fabricating. You also have the "hogshead" from your crashbox trans to use to adapt them to the stock clutch. A T5 will not clear that crossmember, tho. (just barely) There are other trannies that will clear and can be easily adapted including the 4-sp's with 4th being OD that were used in F-150s in the 80's.

 

The confusion about the 1 ton is the fact that in the US the F3 was a heavy duty 3/4 ton and the F4 was the one ton.

If your only goal is to increase your road speed, you really don't need to do both. The rearend swap to a Dana 60 with 3.73 gears will give you about 57-63 mph @2500 rpm depending on tire size. The T5 swap with your stock tire size would give you about 64 mph @2500 rpm.

 

Thanks AXRacer, Ross and Joe. I'm planning to get the truck up on a hoist on Wednesday, and will snap some photos of what's under there. 60MPH would be all I'd need for what I plan to use it for, BTW.

 

Yea, I was in that 45 mph zone with Edith, so I looked at changing the rear end, the transmission, even got an auxiliary transmission with OD, that I never installed. Then the Flathead went down on me. After much hemming and hawing, I got a rebuilt Flathead. I have been babying the new motor, got about 400-500 miles on it now. I took it to a cruise in about a month ago and got caught in some traffic on the way back. My buddy was following me and called to ask what else I had done to the truck. I was puzzled until he told me that we had been running between 57-60 MPH for the last 15 miles. I calculated it out and it looks like I was turning about 3000 rpm and the motor was as quite and smooth as could be. With the old motor, at 45 mph it sounded like I was in a war zone.

 

Harleymsn - that's an encouraging story about the new engine. The engine actually sounds pretty good in our truck - in fact it has a rebuilt stamp so perhaps we'll get some more miles out of it yet.

 

Joe can you share where you got your motor from? I just bought an F3 with an engine issue that will at least require a bottom end rebuild it not some more serious attention.

Thanks Mike

 

dcavan001 - where are you located? I have a Dana 60 from a 65 F-250 with 4.10 gears in it that I'm not going to use. My axle is in central Texas. I'm guessing that isn't very helpful to you since most of the Mercury trucks are at least 1,000 miles north of the axle.

 

I got the motor out of Utah, JMadsen is friends with a retired machinist/engine builder that now rebuild flatheads. Even with the shipping it was way less than was available around here at the time.

 

38 coupe - we are in Vancouver, so at least 1000 miles from where you are. Having said that finding a good bunch of parts is important, and the cost of shipping might be worth it.