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Wont shift when it rains?

stoney126

stoney126

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Hey all, I have a weird problem with the truck no twanting to shift up when it rains. Its a 84 blazer 6.2/400. It will shift when the rps get high enough but the im not a fan of my diesel screaming at 20mph. It only does it when it rains. I didnt even drive it in the rain:confused: Any Ideas?
 
stoney126 said:
Hey all, I have a weird problem with the truck no twanting to shift up when it rains. Its a 84 blazer 6.2/400. It will shift when the rps get high enough but the im not a fan of my diesel screaming at 20mph. It only does it when it rains. I didnt even drive it in the rain:confused: Any Ideas?
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No idea what is doing that.
I know my th400 did that when I had a cracked vacuum line.
Check the vacuum lines or your vacuum pump, I am sure when you see it you'll figure out what is wrong.
 
I had a similar issue with 1990 suburban, 700r4. It wouldn't shift when it was wet, and it was definately a vacuum leak that caused it.
 
Got soft line from the vacuum pump to the tranny modulator? Replace as much of as possible with hardline. Your tranny will thank you for it. BTDT :D

-- A
 
Unlikely, but how is your fluid? Not pink is it?

Had a TH400 in a car that had a bad dipstick seal in it. When it rained, road spray would hit the dipstick, and get into the trans.
 
Im sure the seal is bad, but I havent drove it in the rain and the road isnt wet enough to throw any water up there. I do believe my fluid is pink though? But I check it constantly and levels havent seemed to change?
 
Fluid should be dark red. If it's pink, it's got water in it and is bad. It takes a LOT of flushing to get it out. Need to figure out why water is getting in, fix that, and change the fluid until it's no longer pink.

You also might want to make sure that your radiator cooler (if that's how it's plumbed) is not letting coolant in and/or vice versa. I've heard of that happening as well.
 
lol after I pulled what used to be rubber line and replaced it shifted fine. I changed the filter and luid not to long ago. I could be wrong but it looks like the is a Tc drain as well as a pan drain on my trans. Ill drain em.

What am I looking at as far as changing the seal for the dip stick?
 
Two styles IIRC, (or could be TH350 vs 400) but one style uses an o-ring, one uses an actual grommet.

My car had an o-ring on it from a PO, instead of the grommet, which is why it let water in.
 
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