TH350 issues

[tycharles]

I've got a 85 c10 with a 305 and a th350c and sometimes it takes a few seconds of the truck running to get the transmission to shift into gear. Start up the truck, quickly shift into gear and sometimes nothing happens. Is this normal or something to be addressed? There is also sometimes a faint high pitched whistling noise when the truck is in R, 1 or 2. Doesn't do it in drive. Wondering if there might be a vacuum leak somewhere that may be causing both of these issues. Any help is much appreciated

 

[NickTransmissions]

I've got a 85 c10 with a 305 and a th350c and sometimes it takes a few seconds of the truck running to get the transmission to shift into gear. Start up the truck, quickly shift into gear and sometimes nothing happens. Is this normal or something to be addressed? There is also sometimes a faint high pitched whistling noise when the truck is in R, 1 or 2. Doesn't do it in drive. Wondering if there might be a vacuum leak somewhere that may be causing both of these issues. Any help is much appreciated

Not normal at all; you're having delayed engagements which can be caused by vacuum leaks. These vac modulated transmissions need/rely on a consistent vacuum signal to function properly. So find and fix any vacuum leaks and see if your delayed engagements resolve.

Also, put a vacuum gauge on the hose going to the modulator - see what the vacuum reading is. Should be at least 12hg at idle...Also make sure the modulator is healthy by testing it with a vac hand pump (or simply replace it if it's real old).

 

[tycharles]

I will do that and report back, thank you!