47re downshifting issue

[Iron Duke II]

Went on 220 test drive today with the old camper in tow. The 12 valve pulled well and the 47re did well the whole trip until I approached a stop light the last few miles from the house. The stretch of road leading to the light was flat, with essentially no grade. As I lifted my foot of the go pedal at 55mph and about 400 ft from the intersection the transmission took longer than normal to shift from overdrive to 3rd, shift from 3rd to 2nd seemed ok. At approx 40 ft foot from the stop light, on the brake pedal, the tach remained at about 1100-1200 rpm and the truck seemed to be surging forward as I was applying the brakes. It did stop with more than usual foot pressure and drove another 10 miles home, however it acted up a couple more times along the way.

 

[Iron Duke II]

To clarify, the truck actually tried to move forward while braking and under 4 or 5mph. Wondering if the throttle linkage is binding.

 

[Iron Duke II]

I took the truck on another run across the foothills nearby without the trailer today. On the return leg as I approached a stop light at less than 5 mph, the engine idle went up to 1500 while braking. I had to place it in neutral to force the stop. It did this intermittently a few more time on the way home. Does that sound like a engine, PCM or transmission issue?

 

[GrantP]

Did the engine RPM change when you put it in neutral?

 

[BigPapa]

Your truck’s engine is 100% mechanical, no electronic control, period. You have something wrong with your throttle cable, linkage, or an internal pump problem. I would start by thoroughly inspecting your throttle cable for fraying, then move on to the linkage, bell cranks, and levers. You need to do it NOW, before something happens and you have an accident that causes damage you can’t repair.

 

[Iron Duke II]

I took the truck on another run across the foothills nearby without the trailer today. On the return leg as I approached a stop light at less than 5 mph, the engine idle went up to 1500 while braking. I had to place it in neutral to force the stop. It did this intermittently a few more time on the way home. Does that sound like a engine, PCM or transmission issue?

No it did not. However after the truck cooled down it was back at about 800 rpm.

 

[Iron Duke II]

Your truck’s engine is 100% mechanical, no electronic control, period. You have something wrong with your throttle cable, linkage, or an internal pump problem. I would start by thoroughly inspecting your throttle cable for fraying, then move on to the linkage, bell cranks, and levers. You need to do it NOW, before something happens and you have an accident that causes damage you can’t repair.

The throttle cable does "Not" show fraying, the linkage appears to move normally, no sticking, bell cranks does not wobble. Could it be signs that the TC is failing? It is occurring after the truck is up to operating temp, it was near 100 degrees day. Considering a call for a tow to the shop.

 

[Ozymandias]

It has nothing to do with your transmission, it's the injection pump that keeps the rpm up like @BigPapa said.

 

[Iron Duke II]

If that's the case, I had the transmission shop change the fluid and check out the system recently. They replaced the bushings on the bellcrank.

 

[Ozymandias]

From what you have written it seems that something is binding when the truck is at operating temperature, and that would indicate that it is internally at the P7100. I can't imagine something outside that would be able to bind just from temperature change.

 

[Iron Duke II]

From what you have written it seems that something is binding when the truck is at operating temperature, and that would indicate that it is internally at the P7100. I can't imagine something outside that would be able to bind just from temperature change.

Possibly the bellcrank bushings.

https://powerdrivendiesel.com/product/pdd-bronze-p7100-bellcrank-bushing/

 

[JMcCoy]

I would also check the TV cable at the transmission to make sure it's moving freely and not hanging up.

If the truck is surging forward as you're coming to a stop, but then settles down pretty fast, I would be looking at the transmission. If doesn't settle down pretty fast, I'd be looking at your cables or injection pump. Though unlikely, a bad injector could be dumpling fuel. How are your egts?

 

[Iron Duke II]

I would also check the TV cable at the transmission to make sure it's moving freely and not hanging up.

If the truck is surging forward as you're coming to a stop, but then settles down pretty fast, I would be looking at the transmission. If doesn't settle down pretty fast, I'd be looking at your cables or injection pump. Though unlikely, a bad injector could be dumpling fuel. How are your egts?

It doesn't settle down fast. The injectors have less than 1K on them.

Towing up a 7% grade the other day w/OD off the egts remained under 900F. Normal driving they remain between 600-700F.

 

[Iron Duke II]

Did the engine RPM change when you put it in neutral?

No it did not.

 

[Iron Duke II]

I would also check the TV cable at the transmission to make sure it's moving freely and not hanging up.

If the truck is surging forward as you're coming to a stop, but then settles down pretty fast, I would be looking at the transmission. If doesn't settle down pretty fast, I'd be looking at your cables or injection pump. Though unlikely, a bad injector could be dumpling fuel. How are your egts?

Is the following TV cable adjustment one you've performed?

 

[Iron Duke II]

The local transmission shop I have used for other vehicles has not identified the cause of the issues yet. However, the TV cable and TPS checked out as ok.

 

[BigPapa]

THROTTLE cable, linkage, or pump.

The TV cable and TPS would NOT cause what you describe. If this shop doesn’t know that, they’ll not find your problem.

 

[Iron Duke II]

THROTTLE cable, linkage, or pump.

The TV cable and TPS would NOT cause what you describe. If this shop doesn’t know that, they’ll not find your problem.

There was nothing wrong with the throttle cable or linkage. Internal pump problem??

 

[Iron Duke II]

Transmission shop was unable to get the truck to replicate the issue. If it is the P-Pump, why would it have randomly revved up at low (5mph) speed. I plan to take it for a test run later today. No shops in the area that says they know how to work on the P-Pump can schedule an appt for a few weeks.

 

[Turbo Terry]

That’s becoming a increasing problem for sure. Nobody wants to work on anything old. Even the indys