Th350 lagging/late shift? Please help.

DnS421

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Hey guys so I have a 1981 Scottsdale 4x4 with the th350 transmission and lately I’m having an issue with the trans not shifting properly. I put the truck in drive and it seems like it never wants to shift, I can get almost 30 in 1st gear with the engine revving like crazy before I finally get a shift into second, I’m not sure it ever gets to 3rd gear. If I get some speed and then take my foot off the gas it sometimes makes the trans shift but not always. If I manually shift from 1st to 2nd to drive it shifts fine. Trans fluid and filter was changed in 2016, truck has MAYBE 2k miles since then. Vacuum mod is hooked up
 

Vbb199

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Does it have the proper level of fluid in it now?

Letting off the gas then the trans shifting is usually bad seals maybe

Was it parked for any amount of time ?

Is 2016 the last time it was serviced at all??
 

DnS421

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@Vbb199 it was parked for 2 years, I bought it, drove it for several months and parked for another almost 2 years, I drove it some more and parked it for roughly another year until today. If I remember correctly the weird shifting is why I ended up parking it again.
I got the truck in 2016 and changed the fluid and filter and yes it’s all the maintenance I have done to the trans.
When I checked it this morning it was perfectly at the full hot line but now appears to be overfilled even though nothing was added?
 

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DnS421

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@Vbb199 more info for you or anyone else to work with to hopefully help me figure out the problem. I went out and check and the vacuum line is definitely still hooked to the modulator and the manifold, it is no clogged or brittle. I pulled the modulator off and trans fluid came out of the case but not out of the modulator. The valve behind the modulator moves in and out but not a lot. Not sure how much movement it should have. Moved to the other side and pulled the governor off and it looks great, no apple core, everything was clean and seemed fine. Again some trans fluis did come out but I expected that and don’t think it’s adnormal but I could be wrong. I don’t know anything else to do or check other than adjusting the modulator. Could the adjustment make that much of a difference? Any more ideas?
 

Matt69olds

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Disconnect the vacuum line with the engine running. There should be a noticeable difference in the way the engine idles. If not, the line might be internally restricted. You may have vacuum, but the restriction slows the response the modulator sees.

Is the kickdown cable free to move? It’s kinda common to find cables partially melted from exhaust. It the cable is in the extended position, it might cause funky shift conditions. Pull the cable, it should snap back when released.

Vacuum modulators are 15 bucks at autozone. If there is any doubt, just replace it. They are adjustable, but at most you can change shift points 2-4 mph either direction.
 

R Carnella

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Sounds like a bad governor.
 

DnS421

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@Matt69olds i will replace the modulator and try disconnecting the line and starting the truck when I get home. I haven’t checked the cable yet I wasn’t exactly sure where it was.
 

80BrownK10

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@Matt69olds i will replace the modulator and try disconnecting the line and starting the truck when I get home. I haven’t checked the cable yet I wasn’t exactly sure where it was.
The kickdown runs from the. Carburetor throttle linkage to the transmission. You can follow it down or just look at the trans. It's on the driver side and it's the only cable that's hooked into the transmission.
 

R Carnella

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after you've checked all else,you may want to pull the small side cover and check the governor assy.
 

Mark Ugrich

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first off I think you have overfilled the trans. The level on the dip stick should read one pint low when cold and idling in park.Once driven and warmed up, it should read full idling in park.Put a vacuum gage on the hose at the modulator and check for vacuum.Some models use a restrictor in the fitting on the engine side to soften the shifts.It could be plugged.Governor pressure overcomes modulator pressure to make a shift.Recheck the governor by moving the weights and making sure the valve in the center moves and isn’t stuck.
 

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