PLZ HELP w/ TH400 kickdown - The 1947 - Present Chevrolet & GMC Truck Message Board Network

67mbsc · 04-13-2005, 07:40 AM

Hey!
My 87 has a TH400 with kickdown troubles. I know very little about the TH400 kickdown, how do I adjust it? If I put it in drive, it winds out at 45 mph, but if I downshift to 2nd, it does downshift, some at least! If I start from stop, then shift to 2nd, then to drive at 45, it DOES go into third. PLZ help, it would be greatly appreciated.
Thanks

60-66 Nut · 04-13-2005, 12:23 PM

67mbsc, the 400 has an electronic detent, and they rarely give problems. The switch is usually loated under the dash on the accelerator pedal bracket. It should have 2 wires on it, you can disconnect it to see if that changes anything. If it doesn't help, then you have other problems. I would try replacing the modulator valve first and maybe clean the governor out too. The governor is located on the left side of the trans under the cover with 4 bolts. If you take it out, hold it upside down with the gear upwards, and when you work the weights in and out the plunger valve inside should move freely. If not clean it with solvent and blow it out good with air, lube it with clean trans fluid and check it again. Another possibility could be the electronic detent solenoid on the valve body sticking, but I've rarely seen them give problems. Hope that helps, best of luck.

60-66 Nut

MylilBowTie · 04-13-2005, 10:29 PM

If you remove the govenor also check the plastic gear for odd wear patterns.

67mbsc · 04-16-2005, 07:27 AM

Thanks, I appreciate the tips. I'll try the modulator first.

04-13-2005, 07:40 AM	#1
67mbsc Senior Member Join Date: Jan 2005 Location: Myrtle Beach, South Carolina Posts: 266	PLZ HELP w/ TH400 kickdown Hey! My 87 has a TH400 with kickdown troubles. I know very little about the TH400 kickdown, how do I adjust it? If I put it in drive, it winds out at 45 mph, but if I downshift to 2nd, it does downshift, some at least! If I start from stop, then shift to 2nd, then to drive at 45, it DOES go into third. PLZ help, it would be greatly appreciated. Thanks

04-13-2005, 12:23 PM	#2
60-66 Nut Professional Beer Tester Join Date: Aug 2004 Location: Louisiana Posts: 453	67mbsc, the 400 has an electronic detent, and they rarely give problems. The switch is usually loated under the dash on the accelerator pedal bracket. It should have 2 wires on it, you can disconnect it to see if that changes anything. If it doesn't help, then you have other problems. I would try replacing the modulator valve first and maybe clean the governor out too. The governor is located on the left side of the trans under the cover with 4 bolts. If you take it out, hold it upside down with the gear upwards, and when you work the weights in and out the plunger valve inside should move freely. If not clean it with solvent and blow it out good with air, lube it with clean trans fluid and check it again. Another possibility could be the electronic detent solenoid on the valve body sticking, but I've rarely seen them give problems. Hope that helps, best of luck. 60-66 Nut __________________ 60 Ford F100 Custom Cab 61 Apache Short Fleetside 64 C10 Short Stepside 65 C80 409 V8 5spd(X-Firetruck) 83 GMC 350 Olds Diesel 85 GMC Short Bed 86 GMC Short Bed 90 GMC R3500 Crew Cab 92 GMC 1500

04-13-2005, 10:29 PM	#3
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	If you remove the govenor also check the plastic gear for odd wear patterns. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

04-16-2005, 07:27 AM	#4
67mbsc Senior Member Join Date: Jan 2005 Location: Myrtle Beach, South Carolina Posts: 266	Thanks Thanks, I appreciate the tips. I'll try the modulator first.



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