tow-mater


Dav

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1988
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1988 2.9 auto long bed
towed a trailer for the first time with this truck. trailer and cargo weighed about 2000 lbs.
after 30 miles, the truck started surging from 2700 rpm to 2400 and 5 or 10 seconds later going back up. at first i thought it was trying to shift but it was at near steady speed on flat ground.
any time i slowed down, the fumes would catch up, really nasty fumes. at stops, the engine would idle fine but as i accelerated it would do a few farts and keep going. at one point it started smoking like a major oil leak but there wasn't one.
30 miles later the trailer was unhitched and left. the truck ran fine all the way back.
anyone have any idea what the problem might be?
i have to tow the trailer back next weekend
 


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RonD

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Check the modulator vacuum hose on transmission end, make sure there is no trans fluid in it
 

Dav

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1988
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well, took a while but i found a line from the intake to the back end of the trans. i'm not as limber as i used to be so crawling under stuff is difficult. could not get the line loose to check it
what would cause atf to get into this line? and will it drain back out on it's own?
 

RonD

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If the diaphragm fails inside the modulator then ATF will go into Vacuum hose and some will be sucked into engine causing surging and smoke as it is burned

I am just guessing as to the cause of your symptoms.
When pulling a load engine runs with higher vacuum at speed.
You can check the engine end of the hose for signs of ATF, its a vacuum hose so will only have seen air all its life, should be no signs of any kind of oil.

Transmission should shift oddly as well which you don't mention
 
Last edited:

Nez'sRanger

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1989
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If I remember correctly, my dad's old 1990 ranger had a similar problem going up a certain so hill... It would spew a cloud of atf fluid. Quite freaky actually! After some digging (probably on this site, haha!) he found that the tranny was overheating. He ended up replacing the radiator and he installed a separate transmission cooler. The AC condenser was also shot and blocking air from reaching the radiator, so he deleted the AC as well.
I would look into that possibility as well. If the tranny is overheating, that might explain why fluid is getting in the vacuum hose.
 


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