Well I finally put a tachometer in my 54 F100 with a 76 351W and automatic transmission and 3.92 gears. It was at around 2900 RPM's at 60 and 3200 at 70. Is this good or should I be looking into some lower gears.

Thanks for any input,

Marty

 

Howdy,

You didn't say which transmission you're using.....

It's only an F-100. That makes it fairly light. If you do a lot of highway driving/cruising, I would want taller gears so it would turn around 2400 or less at freeway speeds.

You'll always get better mileage turning slower at cruising speeds and a 351 can certainly handle it.

If you have a C-6, you could consider getting either an AOD (AODE) or E4OD to take advantage of a much higher OD final gear and lock-up torque converter.

 

Marty here is a calculator to play with.
Gear Ratio Calculator
I agree with Rick an AOD would be best of both worlds .7 OD would bring you down to ~2250 at 70 MPH with your current setup.
Good luck in your quest!

 

I believe the tranny is a C-6. I have not crawled underneath to confirm. A E4OD is going to run about $750 for a rebuilt one and another $400 to have someone put it in. I agree it would be the way to go. Maybe the wife will buy it for me for Christmas. She would flip if she new what I have already dumped into this toy.

 

Have you looked to see if the rear end is the stocker? Someone who put a 351 and C6 in the truck would be likely to do the 9" conversion too. If it's a 9" you can change gears easily.

 

Rear end is the Dana 44 with 3.92's. The AOD sounds pretty sweet, but a 9" with 3.55's is probably closer to my budget. I got a line on a 72 9" with 3.55's for a $100. Does anyone have any idea what the total costs would be to get the 9" going if I had someone install do it?

 

Labor costs would likely be similar to a trans swap. Similar work involved. You could need driveshaft mods on either swap. Shifter linkage on the trans change and shock mounts on the rear swap. $100 for the rear is a good deal, but with 3.55's you could still take advantage of the OD trans. Personally, bang for the buck, I'd choose the OD trans over the rear change if you're only going to do one. You'll make up the difference in economy over the first year if you drive it much, and have a quieter and more comfortable ride. Your wife might even begin to like it.

 

I'm not aware of a 9" that was 3.55, they were 3.50. At any rate, I got a '70 9" for $75, it needed a substantial rebuild that cost about $300. You can probably figure on new brakes that cost another $125 (NAPA) and you may want to do wheel bearings, which with a shop installing the new bearings runs another $125. You may need the driveshaft lengthened, which really means a new driveshaft or shortening the donor's driveshaft, and then there's new U-joints at both ends. Figure at least $125 - 200 there. Actually doing the fab work required, to get the pinion angle correct, hard to say what a shop would charge. Shims cost $30 - 60. Moving the perches would probably be a 3 - 4 hour charge. New U-bolts are needed to connect the springs to the new axle, $45 a set.

Just keep telling yourself, "it's a drop-in"...

 

Thanks for all the input. Two questions about the tranny option. First what would be the best to go with? Second, would the driveshaft and linkage would be the only add-on costs?

 

I found a a 4 speed overdrive automatic out of a 91 F150 for $250. Would this be a good one to use?

Thanks for the input,

Marty

 

C6: Pan shaped like Utah, has 17 bolts.

If the 351W is from a car, it could also have a C4 (11 bolts), or an FMX (14 bolts).

You won't find a 1972 9" with 3.55 gears, because Ford never offered that ratio.

Be aware that in 1968/72: Ford offered two different 9's in F100's.

One has 28 spline axleshafts with/without Limited Slip. The other has a 9 3/8" ring gear, 31 spline axleshafts & Traction-Lok.

9 vs 9 3/8: Only FIVE parts are the same: Housing gasket, pinion seal, pilot bearing retainer, one pinion bearing and cup.

EVERYTHING else is different!

 

Ross
Your a brutally honest man . That is however very accurate pricing .

 

Is this a computer controlled trans? My advice to you would be to worry less about the initial parts price and think more about the overall cost for the project, and the benefits derived from the modification. You could find yourself tripping over dollars to pick up dimes.

 

You didn't say what diameter rear wheel/tire you are running. You might pick up a few hundred rpm with a larger rear wheel/tire diameter. I went from a 26 inch rear to a 30 inch rear and picked up 400 rpm's (ie 400 rpm's lower at 60 mph).

 

I have a AOD with my 302 and Dana 44 with 3.92, runs a little over 2100 rpm at 75 mph. I like the combo. I just seems to shift early out of first gear when driving with a light foot because of the 3.92, I think my trans guy just needs to make an adjustment.