TH400 kick down solenoid questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**IT Cowboy** · 02-28-2026, 10:27 PM

I took my truck for a bit of a shake down cruise today since doing a few mods and adjustments. I didnt think think the trans kick down was working quite right so when I got home I put a volt meter on it. It was not coming on until the pedal was mashed hard and the carpet was keeping it from doing that. I adjusted the kickdown plunger that the throttle hits and made it kick in sooner.

I took it for a test drive and when I mash the throttle at around a lower RPM it kicks in ok and pulls decent. When going 30-40 and I stomp on it it pulls but it is gradual and pours it on steady. Is this how it is supposed to work? It wont throw me back in the seat or do burnouts. I take it that is just the nature of the three speed and it having more torque than giddy up.

When I am driving and I reach down and pull the plunger by the throttle manually then I can feel it drag down a bit

MARKDTN · 03-02-2026, 04:01 PM

Allegedly on the under dash version you first make sure that you are achieving wide open throttle just as the pedal hits the floor. Then loosen the switch and push the pedal to the floor. Tighten switch. The switch should be maxed out as well as WOT. Been a long time since I did one so that might not be exact.

**dmjlambert** · 03-03-2026, 10:40 PM

If you are going 30 or 40 and are in third gear and push the pedal to the floor, it will immediately shift to 2nd gear. After you let off the pedal some and arrived at a higher speed you will feel it shift back to 3rd gear.

**IT Cowboy** · 03-03-2026, 10:45 PM

I think the issue is there isnt really an issue. The truck is geared at 3:08 in the diff and 1st gear is high anyway. It is a truck and not a hot rod and was never meant to be. I have adjusted everything and checked the secondaries, the kick down, the trans pressure switch, tuning, air flow and everything in between

**Steeveedee** · 03-03-2026, 11:44 PM

L47 BBC usually came with a 3.56 axle ratio, if equipped with an automatic. Are you sure you have a 3.08? it would be on the SPID, if so.

Accelo · 03-03-2026, 11:59 PM

This is the detent switch adjustment copied exactly from the 1972 Service Manual:
1 Install the switch as shown in Figure 3T.
2. After installing the switch, press the switch plunger as far forward as possible. This presets the switch for adjustment. The switch will then adjust itself with the first wide-open throttle application of the accelerator pedal.

**Steeveedee** · 03-04-2026, 12:44 AM

My Q-Jet was so worn that I replaced it with an Edelbrock AVS. I'm looking for an adapter for the kds. Any ideas? I'm feeling lazy (tired), atm.

**70STOVEBOLT** · 03-05-2026, 05:07 PM

Here is a USA made product:

https://temeculasouth.com/

**Steeveedee** · 03-05-2026, 08:34 PM

^ Thank you!

**IT Cowboy** · 03-05-2026, 10:03 PM

I re-wired it to the IGN wire with a fuse. No difference in how it runs but now I dont have to worry about it.

02-28-2026, 10:27 PM	#1
IT Cowboy Senior Member Join Date: Jan 2025 Location: Arizona in a van down by the river Posts: 617	TH400 kick down solenoid questions I took my truck for a bit of a shake down cruise today since doing a few mods and adjustments. I didnt think think the trans kick down was working quite right so when I got home I put a volt meter on it. It was not coming on until the pedal was mashed hard and the carpet was keeping it from doing that. I adjusted the kickdown plunger that the throttle hits and made it kick in sooner. I took it for a test drive and when I mash the throttle at around a lower RPM it kicks in ok and pulls decent. When going 30-40 and I stomp on it it pulls but it is gradual and pours it on steady. Is this how it is supposed to work? It wont throw me back in the seat or do burnouts. I take it that is just the nature of the three speed and it having more torque than giddy up. When I am driving and I reach down and pull the plunger by the throttle manually then I can feel it drag down a bit __________________ 1972 C10 Custom Deluxe Highlander 402 Freedom isn't safe, it requires you to take responsibility for your own life, your own safety, and your own success. It carries with it the possibility of failure and the understanding that you're working without out a safety net. If you give the state the responsibility for any of these you also give up the freedom that accompanies the responsibility.

03-02-2026, 04:01 PM	#2
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,260	Re: TH400 kick down solenoid questions Allegedly on the under dash version you first make sure that you are achieving wide open throttle just as the pedal hits the floor. Then loosen the switch and push the pedal to the floor. Tighten switch. The switch should be maxed out as well as WOT. Been a long time since I did one so that might not be exact. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

03-03-2026, 10:40 PM	#3
dmjlambert Senior Member Join Date: Apr 2016 Location: Cypress, TX Posts: 4,051	Re: TH400 kick down solenoid questions If you are going 30 or 40 and are in third gear and push the pedal to the floor, it will immediately shift to 2nd gear. After you let off the pedal some and arrived at a higher speed you will feel it shift back to 3rd gear.

03-03-2026, 10:45 PM	#4
IT Cowboy Senior Member Join Date: Jan 2025 Location: Arizona in a van down by the river Posts: 617	Re: TH400 kick down solenoid questions I think the issue is there isnt really an issue. The truck is geared at 3:08 in the diff and 1st gear is high anyway. It is a truck and not a hot rod and was never meant to be. I have adjusted everything and checked the secondaries, the kick down, the trans pressure switch, tuning, air flow and everything in between __________________ 1972 C10 Custom Deluxe Highlander 402 Freedom isn't safe, it requires you to take responsibility for your own life, your own safety, and your own success. It carries with it the possibility of failure and the understanding that you're working without out a safety net. If you give the state the responsibility for any of these you also give up the freedom that accompanies the responsibility.

03-03-2026, 11:44 PM	#5
Steeveedee Ram-A-Lam-A-Ding-Dong Join Date: Jan 2013 Location: Simi Valley, CA Posts: 11,899	Re: TH400 kick down solenoid questions L47 BBC usually came with a 3.56 axle ratio, if equipped with an automatic. Are you sure you have a 3.08? it would be on the SPID, if so. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

03-03-2026, 11:59 PM	#6
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,426	Re: TH400 kick down solenoid questions This is the detent switch adjustment copied exactly from the 1972 Service Manual: 1 Install the switch as shown in Figure 3T. 2. After installing the switch, press the switch plunger as far forward as possible. This presets the switch for adjustment. The switch will then adjust itself with the first wide-open throttle application of the accelerator pedal.

03-04-2026, 12:44 AM	#7
Steeveedee Ram-A-Lam-A-Ding-Dong Join Date: Jan 2013 Location: Simi Valley, CA Posts: 11,899	Re: TH400 kick down solenoid questions My Q-Jet was so worn that I replaced it with an Edelbrock AVS. I'm looking for an adapter for the kds. Any ideas? I'm feeling lazy (tired), atm. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

03-05-2026, 05:07 PM	#8
70STOVEBOLT Senior Member Join Date: Jun 2005 Location: Winona Lake, IN Posts: 7,062	Re: TH400 kick down solenoid questions Here is a USA made product: https://temeculasouth.com/ __________________ 70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Sliding Rear Window Power Windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear

03-05-2026, 08:34 PM	#9
Steeveedee Ram-A-Lam-A-Ding-Dong Join Date: Jan 2013 Location: Simi Valley, CA Posts: 11,899	Re: TH400 kick down solenoid questions ^ Thank you! __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

03-05-2026, 10:03 PM	#10
IT Cowboy Senior Member Join Date: Jan 2025 Location: Arizona in a van down by the river Posts: 617	Re: TH400 kick down solenoid questions I re-wired it to the IGN wire with a fuse. No difference in how it runs but now I dont have to worry about it. __________________ 1972 C10 Custom Deluxe Highlander 402 Freedom isn't safe, it requires you to take responsibility for your own life, your own safety, and your own success. It carries with it the possibility of failure and the understanding that you're working without out a safety net. If you give the state the responsibility for any of these you also give up the freedom that accompanies the responsibility.



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