Th400 Modulator/Shift question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

SunSoaked · 10-30-2018, 10:36 AM

I'll admit I'm ignorant on this topic. Only ever dealt with a 700r4. Got my Th400 back from the shop yesterday, fully rebuilt. I noticed the vac modulator has a red stripe on it (I see black striped ones available as well). Internet search suggests that it's adjustable? Does adjusting it only affect the shift points at WOT? How does adjusting the modulator differ from installing a "shift kit"? They installed a mild shift kit because we both agreed the really hard shifts are annoying on a typical daily driver.

sweetk30 · 10-30-2018, 11:27 AM

i know the red strip is most popular upgrade unit guys use .

it basicly lets you fine tune the point of shift a bit . nothing crazy .

try it first and then play from there .

*Chevyrestorerman* · 10-30-2018, 08:30 PM

Looks like you had to rebuild the ol 400 transmission after all...

is this the truck that got vintage air, any pics of that install ?

SunSoaked · 10-30-2018, 10:00 PM

Ya, it started making noises that suggested it was about to give up the ghost. As far as the Vintage Air, there's not much to see. Everything fits up under the dash. The firewall gets a block off plate. I'm very satisfied with it. It was a pleasure getting rid of all the factory wires, vacuum hoses and relays. Blows 43 degrees out the vents on a 120 degree Arizona day.

*Chevyrestorerman* · 10-31-2018, 08:33 AM

Its a great way to show off your truck's vintage air install, post pic's so others can see how it was done. Thanks in advance.

crazy longhorn · 11-04-2018, 04:45 PM

Quote:

Originally Posted by SunSoaked

I'll admit I'm ignorant on this topic. Only ever dealt with a 700r4. Got my Th400 back from the shop yesterday, fully rebuilt. I noticed the vac modulator has a red stripe on it (I see black striped ones available as well). Internet search suggests that it's adjustable? Does adjusting it only affect the shift points at WOT? How does adjusting the modulator differ from installing a "shift kit"? They installed a mild shift kit because we both agreed the really hard shifts are annoying on a typical daily driver.

My thoughts, are that the modulator, is adjustable for fine tuning on the shift points. I would run the trans as set up, & see how she feels. If you are running lower (numerical gears), you will do better using a govenor recurve kit, to set the shift points. You can use the vac modulator, to fine tune your shifts. Best of fun.....crazyL

10-30-2018, 10:36 AM	#1
SunSoaked Registered User Join Date: Dec 2011 Location: Yuma Arizona Posts: 1,524	Th400 Modulator/Shift question I'll admit I'm ignorant on this topic. Only ever dealt with a 700r4. Got my Th400 back from the shop yesterday, fully rebuilt. I noticed the vac modulator has a red stripe on it (I see black striped ones available as well). Internet search suggests that it's adjustable? Does adjusting it only affect the shift points at WOT? How does adjusting the modulator differ from installing a "shift kit"? They installed a mild shift kit because we both agreed the really hard shifts are annoying on a typical daily driver.

10-30-2018, 11:27 AM	#2
sweetk30 Registered User Join Date: May 2012 Location: horseheads,ny rust belt Posts: 2,794	Re: Th400 Modulator/Shift question i know the red strip is most popular upgrade unit guys use . it basicly lets you fine tune the point of shift a bit . nothing crazy . try it first and then play from there . __________________ 77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great.

10-30-2018, 08:30 PM	#3
Chevyrestorerman Account Suspended Join Date: Aug 2018 Location: GBR !! Posts: 144	Re: Th400 Modulator/Shift question Looks like you had to rebuild the ol 400 transmission after all... is this the truck that got vintage air, any pics of that install ?

10-30-2018, 10:00 PM	#4
SunSoaked Registered User Join Date: Dec 2011 Location: Yuma Arizona Posts: 1,524	Re: Th400 Modulator/Shift question Ya, it started making noises that suggested it was about to give up the ghost. As far as the Vintage Air, there's not much to see. Everything fits up under the dash. The firewall gets a block off plate. I'm very satisfied with it. It was a pleasure getting rid of all the factory wires, vacuum hoses and relays. Blows 43 degrees out the vents on a 120 degree Arizona day.

10-31-2018, 08:33 AM	#5
Chevyrestorerman Account Suspended Join Date: Aug 2018 Location: GBR !! Posts: 144	Re: Th400 Modulator/Shift question Its a great way to show off your truck's vintage air install, post pic's so others can see how it was done. Thanks in advance.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.