1986 th400 Not Shifting Up/Late Shifting

[NDT]

How did you get to timing chain???? Dude, replace the VRV, it is a 32 year old plastic pos. The vacuum level at the transmission needs to vary from about 8 to 25 inches as you move the throttle from wide open to idle. Pau!

 

[cucvrus]

I dropped mine off at the transmission shop and it sat for 3 days. The guy called me and said come pick up your truck it's done. One time it was my fault reversed the vacuum lines. Top to transmission and bottom to back of engine is correct. The second time he just adjusted the vacuum switch. Saved me the head ache and I bought the special KD tool. Both times it was $20. US. Not worth the hassle for me. I messed with it for an hour and said. He built the transmission he can adjust it. Because he was going to warranty it. $20. well spent IMHO.

 

[WARWAG]

Check the 1" hose down on the lower pert of the tyranny. Mine was rotted and I got the same symptoms you are describing. Also one of the vacuum lines had a leak up on the engine. The hose was new but the hard line had a very slight tapper. Defective from the factory. I had the push the hose down 4" or so to get pass that taper and get a good deal. I believe I then added little hose clamps on every hose after that. That transmission shifted like it was new and still does as my neighbor bought the truck from me. It sounds like a vacuum leak for sure.

 

[dom1986ck30]

KEYWORDS: th400, Kick Down Switch (under the tranny pan), Governor, Modulator, Vacuum Port, Vacuum Pump (VP), Vacuum Source, Vacuum Regulator, rubber hoses, metal vacuum line, VRV (Vacuum Regulator), 20"hg, 8"hg, .646 Throttle set, IP (Injection Pump), Patience, a mirror, lubrication, find the Kickdown Switch under the dash.

Aloha... Wanted to take the time to say Mahalo to all on this thread and to the Steel Soldiers site. The combination of the two were a perfect match for the success of my diagnosing the situation that I was in with my 1986 M1008. If you have found this thread then I don't need to go through the history of my situation. I came across a problem that was posted by rustystud. My problem was exactly the same. The more time you spend on this site... the better. The manuals and all the input on this site have an impeccable display of information that make a person like me insist that these vehicles are all to fun!!! So... that being said, I will say that this is a conclusion statement from the originator of the thread. --- Like I said I read and read all through this site. Waited for parts to come in from Amazon. Testing my patience. Diagnosing everything I could think of or read about. Then I stumbled across an article and BAM. I checked the Kickdown Switch under the dash, looked at it's operation & function, then lubricated it. Moved it back and forth. Took it for a spin... SUCCESS!!! Mahalo again!!!...

 

[rustystud]

KEYWORDS: th400, Kick Down Switch (under the tranny pan), Governor, Modulator, Vacuum Port, Vacuum Pump (VP), Vacuum Source, Vacuum Regulator, rubber hoses, metal vacuum line, VRV (Vacuum Regulator), 20"hg, 8"hg, .646 Throttle set, IP (Injection Pump), Patience, a mirror, lubrication, find the Kickdown Switch under the dash.

Aloha... Wanted to take the time to say Mahalo to all on this thread and to the Steel Soldiers site. The combination of the two were a perfect match for the success of my diagnosing the situation that I was in with my 1986 M1008. If you have found this thread then I don't need to go through the history of my situation. I came across a problem that was posted by rustystud. My problem was exactly the same. The more time you spend on this site... the better. The manuals and all the input on this site have an impeccable display of information that make a person like me insist that these vehicles are all to fun!!! So... that being said, I will say that this is a conclusion statement from the originator of the thread. --- Like I said I read and read all through this site. Waited for parts to come in from Amazon. Testing my patience. Diagnosing everything I could think of or read about. Then I stumbled across an article and BAM. I checked the Kickdown Switch under the dash, looked at it's operation & function, then lubricated it. Moved it back and forth. Took it for a spin... SUCCESS!!! Mahalo again!!!...

I'm glad my unfortunate mistake could help someone else. At first I wasn't going to post that since it was a really boner mistake I made. I went straight from problem, "bypassing troubleshooting" into repair. That's a problem even us old crusty mechanics fall prey to. I forgot the number one rule, "never assume anything ! " . I still remember this group of mechanics where trying to get this one bus started. It was a "problem child" meaning that it had all kinds of issues all the time. This time however it was just that no one had fueled the bus ! Busses don't have fuel gauges on the dash since they are fueled everyday and a log of their mileage is strictly kept. Well no one checked the log ! It was out of fuel. They spent over 3 hours on it checking every sensor and all the wiring to the ECM. That was four mechanics at 3 hours each. Twelve man hours wasted because everyone "assumed" they knew what was wrong.

 

[forest522]

This a great bit of info! Rustystud, sorry for your experience the other day, rest assure though - totally human error! Your a better man for actually, openly discussing it and sharing it with us. You likely have saved many people a lot of time!

Regarding the throttle kick down switch, all I need to do is lubricate the sliding mechanism? I've had some trouble with late and rough shifting as well. Transmission shop says the unit is in great shape. All seals have been replaced and I replace the vacuum modulator next to the IP recently. All new rubber as well.

Will check the switch under the dash today, again...just lubricate the sliding mechanism?

 

[dom1986ck30]

Aloha, I had checked the switch down in the tranny pan buy filter it's a little switch called the kickdown switch. I took it to a transmission shop and they said I am golden. Modulator change a few times to be sure before I drop the tranny. My governor was okay no applecore effect per se. Check all vacuum lines. 20 HG inches from the main source. 8 inches HG to the tranny. Follow the setting of the vrv valve in the manual. Super easy. I just cut a piece of wood that was 5/8 inches to put between the throttle screw and the injection pump gauge set. I also replaced the main source of vacuum from the motor. It's the vacuum pump at firewall. After all of that was done and checked and all good, and multiple checks of all vacuum lines, I was very frustrated. So yes check your kickdown switch under the dash. So basically there are two kickdown switches one inside the tranny Again by the transmission oil filter and one underneath the dash. Lubricate the switch under the dash. I ended up soaking mine. And with your hand move it back and forth to get good sliding action. You'll notice the pedal pushes it towards the floor. It is supposed to bounce back up towards the firewall. Hope this helps.

 

[forest522]

Great, I just looked under there and saw it above and slightly to the right of the fuel pedal. I'll remove it today, clean and lube it with silicone or whatever I have handy. Thanks again!

 

[rustystud]

Great, I just looked under there and saw it above and slightly to the right of the fuel pedal. I'll remove it today, clean and lube it with silicone or whatever I have handy. Thanks again!

Yes just spray it good with some PTFE spray. You don't want to just replace it as they cost over $70.00 now for a stupid little on-off switch and only a few places carry them !