I have no idea, is it on a tag outside the rear end or do I have to open it up? I've been collecting parts for a couple years now and can't remember what I bought half the time! I guess I do need to open it up to make sure its usable. I went into this with limited knowledge but I got a lot of determination to finish the job. I'm learning a lot along the way and this forum is a HUGE help.

 

Short of finding a tag on the rear differential, you'll probably have to look at the ring gear. Mine had the ratio stamped on it, or worst case you can just count the number of teeth to determine the ratio.

Sorry... I'm not trying to make it more complicated than it needs to be, but the couple of people that I know on this list that installed C6 transmissions (including myself) wound-up installing taller gears in the rear.

I should have mentioned that the tire diameter affects it too... there are several threads on here about that.

Amen to that brother! I would have been up-the-creek without all the help that I've received from the folks here.

 

Um, …….just wondering if it makes any difference if it is a C6 or any another automatic, (other then a four speed auto with overdrive), as are not all 3 speed automatics 1 to 1 in drive (high gear)?

 

You're probably right... the 1 to 1 (lack of overdrive) is the issue. Don't know what the ratio is on the C4; I assume it's probably 1 to 1 also.

The 2.80 ring and pinion did the trick for me, I can cruise at 70mph and still be around 3000 RPM's or less.

 

That is a good combination, I'm doing basically the same with a 351w. My block is a 69 and lots of later parts fit including heads. My original 351w and c-6 came out of my 77 econoline after she fell all apart with rust. Before this the original 351w gave it up on a camping trip one time so I replaced it with a 69 351w from a mercury comet. Out of curiosity I tried 85 heads on it and it ran good but I think I will put the 69 heads back on. After the van gave it up, I used it in my Cobra replica until I thought I nneded a 429 in it. Now it is destined to spend time in the 49 f1. (I still have the flatty and 4sp trans) that goes in the next project along with the 49's original diff) The c-6 is underneath the motor

 

Hey Kimberly, that must kina’ be some type of transaxle huh, does it work well?

 

Or a chain drive off the flywheel, kinda like a bicycle. With a flick of the left handle, it will switch to the FMX for those "in-between" gears.

 

ha ha ha,.....

 

That will be a really nice drive train when you get it in.

 

It's dependable, it might look dirty and needs a general cleaning. When I used this motor and trans in the Cobra it ran flawlessly. I'm hoping it's First Fire Up in the old Ford will be as memorable as it was with the car.

 

First of all, I want to apollogise sincerely for highjacking your thread.
You wont be sorry if you go this route, there are so many possibilities for this 351w motor.

mervy

 

The C6 is a big tranny... is the aftermarket crossmember all you need to make it fit in these old trucks? (other than the driveshaft of course) Or do you have to make some alterations to the floor / tunnel?

 

You'll have to enlarge the floor cover plate. or buy one of the after-market plates that's already enlarged.

 

Not true, I have a C6 on the back of a 390 FE in my 51 and the transmission cover is fine - darned close (like 3/4 to 1/2 inch) but still fine.

The transmission cross menber in the original trucks is a structural strength member of the frame. You will have to cut it, and replace it with something that not only supports the larger transmission, but also replaces the structural strength of the original cross member.

2.80 is a good rear end ratio, and you will probably need to make sure you have a respectibly sized back tire as well. Mine is 2.79 - 9 3/8" and I run 235/75R15s in the back. I'm doing 65 at 2350 rpm. FYI, 99% of non overdrive transmissions are direct drive (1:1) in top gear.

You WILL have to adjust your rear end pinion angle quite a bit (about 5 to 8 degrees) in order to prevent severe drive train vibration on this long of an engine and transmission on this short of a vehicle.

 

I suppose how far back you mount your engine will affect whether or not you need to modify the tunnel.

Come to think of it, it was probably the shifter that caused my access plate to need to be modified. I have a Lokar shifter that mounts to the top of the C6.