4R100 not downshifting

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Jun 4, 2013 | 10:07 AM

kameronth

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From: North Dakota

4R100 not downshifting

As you may remember I rebuilt my 4R100 a few moths ago. Today I was driving to a job site and about half way through I noticed that my truck was not downshifting. It will start in 2nd and shift all the way to OD but it will not downshift when I get my foot into it. If I downshift on the column it shifts just fine and goes all the way to 1st with engine braking. No CEL and O/D light is not flashing. It has been raining and my truck is pretty soaked. Maybe the solenoid wires?

Jun 4, 2013 | 05:22 PM

redford

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From: Stephensville WI

When you stop at a light or stop sign, and you do not move the gear selector from anything besides "D", does the truck start out in first gear?

Jun 4, 2013 | 06:28 PM

projectSHO89

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From: St Louis

All shifting (unless the lever is in 1 or 2) is controlled by the PCM. Hook a scanner up and look to see if the PCM has commanded the expected downshifts or not.

Jun 4, 2013 | 07:35 PM

kameronth

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From: North Dakota

Quote:

Originally Posted by redford

When you stop at a light or stop sign, and you do not move the gear selector from anything besides "D", does the truck start out in first gear?

Yes but shifts to 2nd extremely fast.

Jun 4, 2013 | 07:40 PM

kameronth

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From: North Dakota

There was no CEL but I was getting code p1120 for the throttle position sensor. I replaced it since its original and was only $25. Still the same issue. I'll have to see if a shop here even has time to run a full diag on the truck to get transmission codes. Everyone is slammed here.

Jun 5, 2013 | 07:16 AM

kameronth

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From: North Dakota

Also, it does not do this about 10 percent of the time. If I shut the truck off for about 5 min and start to drive it will be fine for just a little while then start acting up again.

May 26, 2014 | 05:04 PM

kameronth

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From: North Dakota

Update:

I plan on selling my truck this summer so I decided today I was going to take another shot at my issues since the weather has been warm. About 3 months ago my truck started to make a "whistle" noise under the hood. First thing I though was vacuum. I replaced the 90 degree pcv elbow coming from the throttle body about 4 years ago. At that time it had a hole and turned on the CEL. Power was down but still shifted normal.

Well, I fixed the issue. The 90 degree pcv elbow was collapsing in on itself when the truck got up to temp. Also, the pcv was not sealing properly. I replaced the elbow, pcv and tubing. It shifts great and no more whistle!

So none of the issues were related to my transmission rebuild.