M1008 Transmission?

prairie

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Bloomfield, Nebraska
At -3*F, my son started and drove my M1008 to school yesterday morning. After sitting in the parking lot all day, he started it up about 9:30 last night at -9*F with no problem. Let it warm up 5-6 minutes and headed the 5 1/2 miles home. Drove easy the first mile, but when he tried to get up to the normal 50-55 mph, the engine would race, but he could not pick up speed. When he let off the gas pedal everything was fine, It sounded fine and the engine revved as it should when in neutral or park. He eventually made it home driving slowly in 2nd gear. From his description, I am assuming that the transmission started slipping when it shifted into 3rd gear.
Transmission fluid level was full, color and smell are good. Fluid and filter were changed less than 7500 miles ago.
After sitting in the 35*F heated garage overnight, I drove it about 25 miles today at -15*F with no problems. Dumped a can of Sea Foam Trans Tune in, and drove another 5-6 miles with no problems. It is sitting outside tonight at a current -4*F, and it is supposed to get down to -10*F, so I will get a good test on it in the morning
My guess is that cold caused a valve to stick, and/or seals hardening and shrinking, allowing oil to bypass in a 28 year old transmission.
Anybody else have any ideas or advise?
 

goldneagle

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Check the fluid level. When was the last time the filter was changed? Also check the transmission vacuum modulator valve on the passenger side of the transmission. Its only a $12 part if it needs replacing. I would also check the vacuum hoses. Better to try the cheap stuff than $1000 for a tranny rebuild.
 

Westech

CPL
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cow farts, Wisconsin
I would dump the fluid and slam in a new filter and fresh fluid and a can of good trans seal stop leak.
The stop leak will soften the seals and might get her back in to shape.
When it is butt cold out I let my trucks run at least 20 min if all possible. Seals dont do well at negative temps
in 30 year old equipment.
Also as GE said make sure to check or just go ahead and replace all the vacuum lines and the modulator. It will set you back less then 25 bucks and will eliminate that from the equation.
 

bigbird1

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Transmission is toast. She has one foot in the grave. Needs a rebuild or replaced.
I would have to agree if the fluid smelled burnt. I would bet on some moisture in the valve bank. Like others have said, change the oil and filter. Take the filter apart and look inside the mesh part, ( I pry them apart with a screwdriver) if you see clutch parts or brass then its time to rebuild.
 
479
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Location
Madison, WI
It's a few miles from Deer Sh*ts, WI :beer:


To prarie, it very well could just be the cold. The trans fluid gets thicker, the seals and other rubber bits, and lines get less pliable or could crack easily, moving parts become harder to move. A little moisture could have frozen in one of the vacuum lines.
My car takes a long time to shift for the first few times I accelerate in the morning, its been in the negative temps in the morning here lately.

Like westech said, a fluid flush and little trans conditioner would be a good place to start. That way you can look at the fluid and see if there's something wrong. Checking the vacuum lines too would be a good thing to do too.
 

prairie

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Thanks for all the replies!
As I stated in my original post the tranny fluid was full, looked and smelled normal, and the fluid and filter had been changed a little less than 7500 miles ago.
After sitting outside all night without the block heater plugged in, it started and drove fine at -10*F.
I am going to change fluid and filter, and add "tranny fix in a can".
Any suggestions on what brand of tranny conditioner/rejuvenater to use?
Next I plan to check out the transmission vacuum modulator valve and vacuum lines.
I am assuming they are original, so should I just replace all with new ones, as they are relatively cheap?
 

goldneagle

New member
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Location
Slidell, LA
Thanks for all the replies!
As I stated in my original post the tranny fluid was full, looked and smelled normal, and the fluid and filter had been changed a little less than 7500 miles ago.
After sitting outside all night without the block heater plugged in, it started and drove fine at -10*F.
I am going to change fluid and filter, and add "tranny fix in a can".
Any suggestions on what brand of tranny conditioner/rejuvenater to use?
Next I plan to check out the transmission vacuum modulator valve and vacuum lines.
I am assuming they are original, so should I just replace all with new ones, as they are relatively cheap?
Yes i bought mine at Advance Auto Parts and I spent less than $20 for all the vacuum lines and the modulator valve. Make sure you change the vacuum lines including the small ones on the front of the engine.
 

WARWAG

Active member
Lucas Oils rock! I still think the trans is on its last leg but "IF" it can be "fixed" by oil fix it products then Lucas Oil is the stuff to try. By chance did you have the fluid recirculated and new stuff transferred in at the same time? Is so then there is a very good chance the circulation stirred up 25 years of accummulated crud off the bottom of the pan and deposited it on/in to your filter. This will starve the trans of the oil it needs and kill it.
 

WARWAG

Active member
Thanks for all the replies!
As I stated in my original post the tranny fluid was full, looked and smelled normal, and the fluid and filter had been changed a little less than 7500 miles ago.
After sitting outside all night without the block heater plugged in, it started and drove fine at -10*F.
If it drove fine then that doesn't sound like it has one leg in the coffin. It could have been a simple vacuum leak and your son took the high RPMs as it slipping. IF it went into 3rd gear and if it was indeed slipping then its dying and on its last breath. That doesnt usually fix it self over night. BUT if it was staying in 2nd and not going into 3rd (reason for high rpm) then it sounds like either a bad vacuum line and or a bad Modulator. The vacuum lines are super cheap to replace. I would start there. Especially the short one on the side of your transmission going to the modulator. That one is about 1-1/4" long and gets all of the road spray and crud being shot up from your tires ect. Start there and replace all of the lines. This is the simplest thing to do and even if its not the lines then you will have a new fresh set of lines after you replace or rebuild the trans. The modulator could also be the culprit. Either way change out the lines before you change out the oil and filter. Since its was just changed 7500 miles ago there is no sense in changing it now. If it smelt burnt then yes. It really sucks when the problem isn't there when you try and diagnose a problem. Makes us arm chairs mechs guess at what the problem could be. Good Luck.
 
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