M1008 lose of speed, have replaced fuel filter, glow plugs

[ssgtwright-usmc]

My M1008 seems to be having problems lately with gaining and maintaining speed.
When I get about 35mph the engine seems to produce high RPMs so I have to let go of the gas to lose the high RPM and accelerate again before the whole thing happens again at around 45-50 mph.
I have done my regular maintenance a few months back by changing all oils, all filters and even the glow plugs have been changed out for new.
I am hoping that may be a easy fix for now and not a expensive one since I cant even afford to fuel my truck due to the high costs of gas and everything else.
Any help would be greatly appreciated.

 

[K9Unit]

Okay, I'm a little confused reading this thread but I'm sure its just me since I have been up all night working. Does your 1008 engine seem to run fine and when you start to accelerate feels like its not picking up enough speed compared to how fast the engine is running. Does the engine feel like its hesitating, stumbling, ect. ? what happens when your up to speed and you mash down on the throttle ? Please elaborate...

 

[CCATLETT1984]

Um.... Sounds like your describing a shifting problem. Can you try to be a bit more descriptive?

 

[maritimer]

sounds like its missing its shifts and not an enigne problem, look into a trans problem , possibly torque convereter orr in need of service/ rebuild

 

[ssgtwright-usmc]

Seems like my truck drives fine up to the point of reaching 35mph, which sounds like the RPM is running high.
At that point, I will depress the gas pedel till the RPMs drop then when it drops is when I press the gas to get more speed
How much will a new torque converter cost?,

 

[CCATLETT1984]

before you go throwing parts at it, let me see if i understand what your describing.

You start driving the truck around, when you reach 35mph the truck does not shift, you then give it more pedal and the truck shifts?

 

[OLDCHEV4X4]

I think he's letting off to make it shift. Time for a trans rebuild?

 

[CCATLETT1984]

either that or the regulator/rubber lines are shot.

 

[ssgtwright-usmc]

Correct, I have to let off on the gas for it to catch the next speed. Im hoping its maybe a regulator valve or breather valve first before I have to rebuild the transmission.
I am also wondering could it be bad fuel since it happens when I am at 35mph.

 

[CCATLETT1984]

nothing engine related.

There are two rubber hoses on the passenger side of the injector pump, check that they are not rotted (I'd just replace them) also check the lines on the vacuum pump (where the distributor would be on a gasoline chevy).

Report back.

 

[ssgtwright-usmc]

Go look now, hopefully it is just the gaskets and nothing major like a rebuild.

 

[ssgtwright-usmc]

No leaks to be found at the vacuum modulator.
I also forgot to mention that when I am driving up a incline their is a major loss of speed.
I basically live at sea level but when I do get a hill, major loss of speed.

 

[K9Unit]

Doesn't sound good, but try manually shifting it through 1st 2nd and 3rd gear and see if it will hold through each gear and gain speed that way, I think I know the end result but try this first....

 

[ssgtwright-usmc]

Have tried shifting gears on inclines, speed does not increase at any gear change.

 

[maritimer]

my friend it does sound like you may be due for a trans rebuild,

 

[K9Unit]

I would pull the pan and check your filter/ replace. when you drain it if the fluid smells out of the ordinary and appears real dark you have burnt clutches/ bands. If it looks good and you have checked your cables and vaccum line. I would take it to a reputable trans. shop and have them check the line pressure. Note you can do this if you have pressure gauges that will read from 100-500 psi but not everyone does.

 

[CCATLETT1984]

time to visit the trans shop, i'm afraid.

 

[ssgtwright-usmc]

Im afraid to ask but what will the average cost be for a rebuild for a TH-400 transmision?

 

[OLDCHEV4X4]

The last th400 i had rebuilt cost me $600.
And that included the new torque converter.
This was done by a good friend of mine, so i'm sure i got a discount.
I took the trans out and put it back in myself. So no labor charge for R and R.

 

[ssgtwright-usmc]

What size and what type of torque convertor should I be looking for.
I will be using the vehicle for highway use and towing. I do not need anything like street racing.
Any brand name I should be looking for, size and bolt pattern?