TH400 kickdown

[JJSZABO]

Believe me Vile, I DO trust you.

I am trying to learn something in the process.

Thanks for your help

[zieg85]

Thanks for setting me straight on the 2-1 downshift.  I did not know that...  That is one reason why this is the best site bar none for the information you need.

[Laderhosen]

The detent solenoid, modulator pressure, line pressure and governor pressure all dictate where it will shift, when it will shift and it will delay an upshift or force a downshift. Without the detent solenoid working you are strictly relying on governor and modulator pressure and will most likely never see an automatic 3-1 downshift. If the detent solenoid is working and is adjusted correctly you better believe it will do a 3-1 downshift!


The factory settings are under 50 mph 3-1 downshift and 3-2 downshifts under 75 mph in drive range.

DETENT VALVE - Affects regulated modulator pressure tending to hold the 1-2 shift and 2-3 shift valves in the downshift position and provides areas for modulator and detent regulated pressuresfor detent 2-1, 3-1, and 3-2 downshifts.

Trust me, my first transmission was a TH400 and I've always had one since I've had vehicles. I've built a lot of them too. If yours won't 3-1 downshift check out your switch adjustment.

Well my road test confirms it's not downshifting with the detent switch, will get a wire tester on the connector at the gearbox to see if it's receiving current. When you say adjust the switch, what does this involve??

[VileZambonie]

The switch should self adjust but you can also manually adjust it. Trial and error is probably the easiest method. If you absolutely have to floor it to energize the solenoid you need to adjust it to be more sensitive. Just go right down to the connector with a 12v test light (key on Engine OFF) and have an assistant depress the throttle slowly. The test light should light up when the switch closes.

[Laderhosen]

The switch should self adjust but you can also manually adjust it. Trial and error is probably the easiest method. If you absolutely have to floor it to energize the solenoid you need to adjust it to be more sensitive. Just go right down to the connector with a 12v test light (key on Engine OFF) and have an assistant depress the throttle slowly. The test light should light up when the switch closes.

When you say adjust what is it that you actually adjust? The location of the switch? Moving it so the pedal strikes it earlier?

[joesgarage71]

When you say adjust what is it that you actually adjust? The location of the switch? Moving it so the pedal strikes it earlier?

Adjust the switch above the pedal.Yes earlier.

[Laderhosen]

The switch should self adjust but you can also manually adjust it. Trial and error is probably the easiest method. If you absolutely have to floor it to energize the solenoid you need to adjust it to be more sensitive. Just go right down to the connector with a 12v test light (key on Engine OFF) and have an assistant depress the throttle slowly. The test light should light up when the switch closes.

Right - I finally got myself into gear and decided to have a look at this!

I simply couldn't find any kick down cable going into the transmission.

So I traced it from the switch under the dash - someone had disconnected the kickdown cable from the transmission and left it lying across the top of the engine!!!!!!!!!!!!!!!!!!!!!!!!!!!!!   

I've plugged it back in and it runs so sweet, and kicks down perfectly!! 

[VileZambonie]

Are you talking about the electircal connector? That was disconnected?

[Laderhosen]

Yep! Why someone would disconnect it and not put it back is beyond me!

[leadlobber7]

The switch should self adjust but you can also manually adjust it. Trial and error is probably the easiest method. If you absolutely have to floor it to energize the solenoid you need to adjust it to be more sensitive. Just go right down to the connector with a 12v test light (key on Engine OFF) and have an assistant depress the throttle slowly. The test light should light up when the switch closes.

I know this post is from quite a while ago but I was reading through the Forum as I noticed the kickdown module under the dash. Please take a look at this picture and tell me what you think rather than adjusting the location do you think that this shim by using a hose would work?

Sent from my SM-G930V using Tapatalk

[VileZambonie]

I am sure many of us have a similar "modification" but if it works to actuate the switch appropriately then it is doing its job. I would first suggest adjusting the switch but adding the hose can help fine tune it.