TH400 Shifting Late

[Mainsail]

I know there are a lot of old threads on this, but I will need help with physical locations of the various parts and that's often left out.

Driving to work this morning I noticed the transmission shifting late from 1st to 2nd (high revs) and while at slow speed I don't get any shift from 2nd to 3rd.

Guessing it's vacuum related, but I welcome all suggestions and help with locating the lines and pump. Truck has been so reliable I haven't had to do much more than oil changes in a couple years.

 

[cucvrus]

First check the vacuum hoses and make sure the hose is still connected to the modulator on the passenger front side of the transmission. If still connected check the vacuum block on the shift modulator of the injection pump and carefully inspect the hoses connecting there. The long one runs back to the vacuum pump at the rear of the engine. If they appear good carefully disconnect the hose from the vacuum pump and carefully start the engine and check to see if vacuum is being created from the vacuum pump. It may make a chirping sound and if you put your finger tip over the 3/8" outlet connection on the pump it should have slight suction/vacuum. Report back on your findings. I check that and then I take it to a reliable transmission shop and fork out $20. and they adjust the shifts for me. It takes the guess work out of it and I trust the guy because he rebuilds all my transmissions. Take Care and Be safe.

 

[Mainsail]

Thanks cucvrus, I hoped you'd chime in!

After work I popped the hood and took a look.





Could it be this easy?

I cut the hose back a bit and stretched the two lines together and took it around the block- seems to be shifting normally.

Drove down to the napa and had the guy cut me 2' of replacement hose so I'll have some extra. He measured out two feet using the floor tiles, plussed it by a couple inches, and cut the hose off the roll. Then he looked all over the roll and couldn't find the SKU anywhere, so he told me to take it no charge.

 

[Mainsail]

I'm a little worried about this piece here as it's also looking pretty dry and cracked (at least on the surface).

It seems to be just a splitter, but I know that sometimes they are more specialized - one side may have more restriction than the other.

Easy part to find?

 

[cucvrus]

Remove that piece and toss it. That was a piece they put on the hose so it fit on the valve one way. Easy to remember top T to transmission and bottom B to back of motor. That rubber block made assembly idiot proof. It does nothing but make a leak when cracked. Good Luck.