Turbo 400 Question

[Matt S]

My M1031 has around 46,000 on the odometer and 170 hrs on the generator. When I'm coasting down a hill or coming off the ramp from highway speed, the truck seems to release off and on from transmission braking.

Is this normal or a sign that something isn't right?

I relatively little experience driving an automatic.

 

[Drock]

Do you mean between down shifting? Also sometimes if your going around a curve the right way the rear locker will wind up & break loose. Causing the truck to kind of shimmy strangely.

 

[Matt S]

Do you mean between down shifting? Also sometimes if your going around a curve the right way the rear locker will wind up & break loose. Causing the truck to kind of shimmy strangely.

No. This is different. The engine is at higher RPMs so should be no chance of the transmission down shifting. The truck is coasting or decelerating and seems to release from compression braking.

 

[rustystud]

The TH400 doesn't allow for compression braking in the "D" (drive) position. If you want the engine to help with that you need to manually shift into second gear. The "intermediate" band only applies in manual second, otherwise your using the "one-way" sprag which will "Not" hold the engine back. The transmission will hold for a few seconds in third gear then "freewheel" until road speed forces the downshift into first gear. Just the nature of the beast.

 

[MarcusOReallyus]

I don't know much about transmissions, but I learn more every time Rusty comments on the subject.

 

[Matt S]

The TH400 doesn't allow for compression braking in the "D" (drive) position. If you want the engine to help with that you need to manually shift into second gear. The "intermediate" band only applies in manual second, otherwise your using the "one-way" sprag which will "Not" hold the engine back. The transmission will hold for a few seconds in third gear then "freewheel" until road speed forces the downshift into first gear. Just the nature of the beast.

Ok. Just wasn't sure if something wasn't slipping or trying to hold but failing. I wouldn't expect this thing to down shift at 55-60 mph.

 

[rustystud]

I don't know much about transmissions, but I learn more every time Rusty comments on the subject.

Thanks Marcus for the encouraging words. I've been kinda depressed lately after learning I had a heart-attack last week.
I had to go for my regular check-up and told the doctor it felt like a 200Ibs man was sitting on my chest. So he performed an EKG. The nurse ran out of the office and the doctor came in and said I had had a heart-attack ! He gave me some "Nitroglycerine" tablets and the ambulance came and took me to the hospital. I had to spend the night there going through a bunch of tests. I still need to go for some more this monday. So I've been sort of worried and depressed and not really caring about much lately.
So it is nice to hear that people are thinking kind thoughts about me.

 

[royalflush55]

Hang in there Rusty, we're praying for a full and speedy recovery. We still need your knowledge on a lot of things!!!

 

[MarcusOReallyus]

Thanks Marcus for the encouraging words. I've been kinda depressed lately after learning I had a heart-attack last week.
I had to go for my regular check-up and told the doctor it felt like a 200Ibs man was sitting on my chest. So he performed an EKG. The nurse ran out of the office and the doctor came in and said I had had a heart-attack ! He gave me some "Nitroglycerine" tablets and the ambulance came and took me to the hospital. I had to spend the night there going through a bunch of tests. I still need to go for some more this monday. So I've been sort of worried and depressed and not really caring about much lately.
So it is nice to hear that people are thinking kind thoughts about me.

Hey, you sound like my dad. He was having a routine physical and after an EKG the doctor asked when he'd had the heart attack. Dad asked what he meant, and the doctor replied that the EKG showed that there was some damage which indicated a previous heart attack. My dad said, "Oh, I guess that must have been the chest pain I had a few years ago."

He'd had a heart attack and just toughed through it!

Oh by the way, he was about 45 when he had that first (?) heart attack, and he lived to be 86. Along the way he blew out his aorta valve and nearly died, but a quadruple bypass kept him going for another 20 years. The evening before his last heart attack he was up on the roof of the neighbor's house, fixing a vent pipe.

You ain't done yet, buddy!

 

[Keith_J]

TH400s are vacuu controlled. Diesel engines don't have vacuum so the DD6.2 uses a vacuum pump and a vacuum regulator on the side of the IP to simulate gas engine vacuum.

Check this system if shifting issues are present. Sure sounds like this is the problem.

 

[rustystud]

Hey, you sound like my dad. He was having a routine physical and after an EKG the doctor asked when he'd had the heart attack. Dad asked what he meant, and the doctor replied that the EKG showed that there was some damage which indicated a previous heart attack. My dad said, "Oh, I guess that must have been the chest pain I had a few years ago."

He'd had a heart attack and just toughed through it!

Oh by the way, he was about 45 when he had that first (?) heart attack, and he lived to be 86. Along the way he blew out his aorta valve and nearly died, but a quadruple bypass kept him going for another 20 years. The evening before his last heart attack he was up on the roof of the neighbor's house, fixing a vent pipe.

You ain't done yet, buddy!

Thanks Marcus, that's good to know that a heart-attack doesn't need to be the end of things !
I do know that I will be changing my eating and exercise habits though. I guess it was God giving me a slap up-side the head to change my bad habits !

 

[rustystud]

TH400s are vacuu controlled. Diesel engines don't have vacuum so the DD6.2 uses a vacuum pump and a vacuum regulator on the side of the IP to simulate gas engine vacuum.

Check this system if shifting issues are present. Sure sounds like this is the problem.

The "OP" was referring to engine braking, not how the shifts are controlled. Though your correct about the vacuum. Actually it is vacuum and governor pressure that controls all shift points. That and throttle position for downshifting (the switch on the throttle lever) .