Truck not down shifting

Hercules-550 · Aug 28, 2016

Hi All,

I had a Ford reman 4r100 dropped in my truck just over 3 years ago. Had issues with hills from day one. Took it back to the shop that installed it and they said there was nothing wrong with it. So I drove it more and issue still persisted. Anytime I was going up a decent incline the truck would slow down to 40 mph before downshifting into 2nd. Would go from OD to 2nd. Would be screaming. I would have to let off the throttle and let it shift back into OD. Then would ride 40 mph the rest of the way up the hill/bridge. Took it to 2 different ford dealers. Both said no issues with the trans. They would do nothing for me. I found a local trans guy and he said it could be the throttle link. The signal from the pedal to the engine. That it is not telling the trans to shift out of OD and into drive.
Has anyone ever heard of this? If so how do I fix it? It is killing me every time I hit a bridge or drving through the mountains.
Thanks

jngreen · Aug 29, 2016

Do you have a chip? It sounds like a tuning issue to me. Something is not playing nice with your f550 gearing. The only other thing I can think to check is the MAP sensor and the rubber hose attached to it. I had a 7.3 that broke that hose one time and the power was still good because of tuning, but the shifting was weird because the computer was shifting off of default mph values and not load.

Justin@DP-Tuner · Aug 31, 2016

So the problem is that it will not downshift into 3rd?

I second the question of you having a chip. Doesn't say so in your sig, but just curious.

Hopefully Mark Kovalsky sees this thread. He was a Ford Trans engineer and can diagnose just about any 4r100 trans issue.

Hercules-550 · Aug 31, 2016

I had the Edge with attitude in it before the trans was replaced and till about a year ago. It was messing up the IDM so I removed it. Local trans guy said it could be electrical between the pedal and intake. It is usually when towing, going up hill/bridge, the truck will slow to 40 mph. Then kick out of OD and into 2nd. If I let off the pedal then it shifts back to OD. Can't find anyone local who can figure it out. Ford tells me I'm out of luck because I live in Florida and there are no big hills here. I am looking for a tuner/programmer to replace the Edge. I was told TS 6 position is a good inexpensive tuner. Still need to reslove the shifting issue before I get a new tuner. Hope this helps.

jngreen · Sep 1, 2016

What happens when you lock it out of overdrive with the button on the shifter.

Hercules-550 · Sep 3, 2016

If I lock it out of OD it won't go into OD. It will go thru the gears from take off. And with the rearend gears the 550 is born with it screams over 50 mph.

jngreen · Sep 4, 2016

Hercules-550 said:
If I lock it out of OD it won't go into OD. It will go thru the gears from take off. And with the rearend gears the 550 is born with it screams over 50 mph.

Yes, but can you can also use it to manually downshift into 3rd while pulling a hill. It should work and could be a solution to your problem until you figure out what the real issue is. Just hit the button again after you pass the top of the hill.

Did you look at your MAP sensor tubing for major cracks or other potential leaks? To me, it sounds like it doesn't know it's under load, so it doesn't fuel harder when it's under load, and then it doesn't downshift properly. However, that wouldn't explain why it skips a gear when it downshifts. Are you absolutely sure that it downshifts into 2nd gear?

Hercules-550 · Sep 5, 2016

If I am running 65 at the base of the hill and push the OD button to take it out of OD and into D, it will try to shift to 2nd. I have tried it...many times. At least it feels like 2nd, it is pretty close to red lining.

jngreen · Sep 5, 2016

Assuming that your truck has 4.88's, your truck will only run 40-45 mph in second gear before you run out of rpms. I wonder if the truck is actually downshifting into 3rd gear with the torque converter unlocked.
Third gear will probably top out at 65mph. This is of course dependent on what tires and gears you are actually running. How much weight are you pulling? In wondering why you don't have the power to pull those hills in overdrive, or why the truck slows down so much.

Hercules-550 · Sep 5, 2016

It has stock size gears. Running 245/70/19.5 tires. Stock are 225/70/19.5. As for weight, my gooseneck trailer is 38' and empty weight at 6500 lbs. And I have had the issue pulling 4000 lb boat/trailer. I never had the issue before putting in the reman Ford trans. I had taken it back to the diesel shop that installed it. They said nothing is wrong with it. I then took it to 2 different Ford dealers to have it looked at. Both said no issues. I called Ford's warranty department, they told me I was out of luck unless I took it to a dealer where there were hills/mountains so they could get it to do what I was telling them. Also would have to leave it so they could go through the warranty process. It was supposed to be a nation wide warranty. But the Florida dealers couldn't do anything. So the warranty ran out a couple months ago. I took it to a local trans guy and he said the Ford computer is very finicky that it would throw a code at the littlest issue. He believes that it is a throttle response issue. That it is not telling the trans to shift out of OD and into 3rd. I have yet to find someone to figure it out.
As to not having the power... I am lost.