Thanks for the tips. I will check the tach to see if it is set right. I had not thought of that. Then next time it is warm enough here to drive her I will manually shift and see if it seems to be going into third. I will also verify the rear end gear ratio while I am at it.

If it would turn out to be the tranny not going into third what would the likely causes be? The transmission has less than 350 miles on it.

Thanks
Alan

 

Guys,
Here's a online calculator where you can put in wheel size and rear end ratio and rpm and get estimated speed. Might help you figure out what rear end ratio you want to run.

Stan Weiss' - Automotive Performance Software / Interactive JavaScript to Calculate Speed(MPH) for given RPM, Rear Gear Ratio and Trans Gear Ratio

 

A bad vacuum modulator will delay shifts, but I don't think it will completely prevent them. But it's the first thing I'd check. Make sure it's getting vacuum.

 

Vacuum modulators are also adjustable. At least mine is. You can tighten or loosen the screw which is inside the vacuum port/hose nipple. It doesn't make a drastic difference in shift point in my experience though.

We also have a kickdown linkage in the mix here too right?

 

You really need to know where you're starting from, so start with determining your gear ratio. I pull the cover and count teeth, but Ross's method works too. Either way you've got to get the axle off the ground so you can turn things. Your C4 will have a 1 to 1 top gear, so the only variables will be the rear tire height and axle ratio. Make sure you really have a low axle ratio and the engine is really taching high. I bought a jeep once from a guy who hated it on the highway. Said he couldn't run faster than about 50-55 because of high engine rpm. After finding the gear etc to be OK, I replaced the giant 7 blade solid fan with a clutch fan. He was mistaking fan noise for high engine rpm.

 

If your having issues with the transmission not shifting into 3rd, I would try and see if the transmission will shift using the manual method. NOT in drive, but go from L, 2nd, 3rd. That will tell you if you have vacuum issues or not. If it's shifting fine manually, and not in D, the modulator or a low vacuum from the manifold may the be problem. If it's not shift manually to 3rd, it could be a valve body or the servo which I would recommend having a tranny shop look at. BTW- if your messing with the vacuum modulator, your not suppose to adjust it either way more than a 1/4 turn, or you'll end up buying a new modulator for sure.

 

My book doesn't break down the models or even give the codes for the rear ratios but my 56 F250 has 4.86 and very likely yours does too if they are original. As mentioned, it's easy to find out.
But with stock 31-32 inch tires, I would stay in the 3.73 range unless you want a real dog. 3.54 maybe but a 3.00 or 3.25 may find the engine below the power band and lugging too much. Do the math and find a gear ratio that matches the tire diameter to keep the cruising rpm in the 2200-2800 rpm range. It's a heavy pickup and any cruising rpm much less than 2200 will find you mashed to the floor on hills just to keep up cruising speed.
Just my 2 cents. Other opinions may vary.

 

I also have a 289 with a c4, but I have a Ford 9" with 2.75 gears. It's the original drivetrain from a 68 Farilane. When I'm going about 65 to 70 mph, my Moon tach reads about 2300 to 2400. So unless it's not shifting into 3rd I say change the rear. It's may be a pressure problem in your tranny preventing it from shifting. My 2cts. Good luck with it.

 

The reason I'm recommending 3.00 or 3.25 is the fact that I'm running a 289 with a C4 as well. I have a 9 inch Ford with 3.50 gears. I'm running 28" tall tires on the rear. At 60 mph, I'm taching at 2800 rpm. The engine is screaming. I had 2.75's in it and it was no where near a dog, but didn't have the acceleration around town. Highway? 60mph, and taching a comfortable 2100 rpm. No need to stay in the slow lane and have people extending their finger at me. I prefer the 3.50's because most of my driving is around town and not long distance highway driving. If I do hit the highway, I stay around 55mph and in the slow lane with the big trucks.

 

Thanks to everyone for the pointers and things to check. It is supposed to be warmer this next week so hopefully I will get a chance to drive her again and try manually shifting as well as checking the other things mentioned.

I hope it is not a problem with the transmission but the way things have been going it would not surprise me. One of the reasons I bought the truck was because it had rebuilt 289 and new Sizzler C4 (less than 300 miles on both). However the truck had been sitting for around two years after the PO had installed them so nothing would be covered by the original warranties. I already had to replace the lifters on the 289, I hope the tranny does not also need work.

 

Might be able to go to a 3.00 or 3.25 with the 9" rear, but the highest I've been able to find for a Dana 60 is 3.54. I've heard rumors of something like a 3.33, but no luck finding one. At any rate, I think the 3.54 is gonna do the trick. Thanks for the help guys, I'll report back when I've got it sorted. Feel free to do the same, oldwi. Seems this thread has enough info pertinent to both.

 

Thanks. I did not mean to hijack the thread but your post sparked my question as we both have the same type of motor and tranny. There is a lot of good help on these forums.

 

3.54 will be OK with any tire size one would likely run. I have been running around for 10 years on a 302 with 3.90s. I am switching out to some 3.2Xs soon, but not because the cruise rpms were outrageous, just trying to make it more fuel efficient.

 

I was going to guess that it is set to the 6 cylinder mode. Do you have a tachometer/dwell meter that you can hook up so that you have something to compare to the tach in the dash?

Coyote....some of those Dana 60's came out of trucks with really low gears. An AOD probably wouldn't fix the problem. You should see about getting a new set of gears installed. With a small block and a C4, you'd probably be pretty happy with anything around 3.25:1, but your gear selection does depend on what your tire size is.

Dan

 

AFAIK, 3.54 is as high as you can go with a Dana 60.
The 61 had differences (the details of which I forget) that allowed higher ratios than the 60 could accomodate.