Need info ASAP !!!

[Spray-Bomb]

Ok guys,

I have a turbo 400 in my truck & it has started to shift late, so I assume that it is the vacuum mod.

I need to know what it takes to adjust the mod.
Tools / what to do

Thanks, Matt

[Longhorn Man]

itty bitty screwdriver.
Remove the vac line, stick screwdriver in, and turn counter clockwise if i remember right.
before that, inspect all the hose to the mod for cracks and rips or pinces.

[Spray-Bomb]

Thanks

Is it flat or phillips ???

[Bishops Trucks]

Flat Head. They don't cost much and are simple to change.

[68C15]

did the engine mysteriously start smoking lately? may be a bad diaphram in the vac. modulator.

[mnunn454]

I don't think most stock modulators are adjustable, but 1st, make sure the vacuum line's in good shape. No sense fiddling/replacing the modulator if it's a bad vacuum line. Also, put a vacuum gauge on the intake and make sure you've got decent manifold vacuum. If it's very low it'll affect shifting too.

[VetteVet]

Here's a good read on transmission shifting.

http://yarchive.net/car/transmission.html

[Texasdeere]

Originally Posted by VetteVet

Here's a good read on transmission shifting.

http://yarchive.net/car/transmission.html

Great Link!

[GMC AMI]

All the 400 turbo's I have seen are all adjustable. As the longhorn dude sugg.
Very easy to fix. I adj. mine to shift into 3rd at 30 MPH with a 500 Caddy engine. I also ran a toggle swith to the electrical hook-up to shut power off when I wanted a delayed shifting point. With no power to the tranny, it will shift much later at a higher rpm and MPH. Much like a economy mode and a rip your head off balls to the walls mode.

[eedgell]

If my younger days are remebered correctly, you can adjust the 400 to shift at about 6000 rpm if you want out of first gear. Alot of fun when your young, dumb and full of huyee!! The point being that the modulator is very adjustable. Check those vacuum lines first!!! Seen a lot of problems solved by replacing them even when they look good. A vacuum leak will cause the tranny to shift late.

[Spray-Bomb]

Thanks guys

I'm about to go out & start trouble shooting it

[GMC AMI]

Originally Posted by eedgell

If my younger days are remebered correctly, you can adjust the 400 to shift at about 6000 rpm if you want out of first gear. Alot of fun when your young, dumb and full of huyee!! The point being that the modulator is very adjustable. Check those vacuum lines first!!! Seen a lot of problems solved by replacing them even when they look good. A vacuum leak will cause the tranny to shift late.

As others have stated, vac. line check is mandatory before anything else. Rubber and steel lines degrade over time and cause most of the problems.
If you want full huyee, ( I never heard that term before so thanks for that! ) And gas milage the toggle really works great! Just remember to have in the right position for the type of driving you really want to do. Hasn't
anyone else done this???

[Spray-Bomb]

My kick-down switch is just a push button, funny when somebody rides with & I press it they think I have NOS... lol

I trouble shot it & it was the mod.
So I'm glad it was something simple

[krue]

Glad to hear it was easily fixed.

[special-K]

I learned goog info here.I never liked the low 1st in a TH400 and prefered to build TH 350s for that reason.At least in a sporty truck.I appreciate the extra beef in a HD truck.

[BACKYARD88]

Glad you got her fixed, I'd hate to have to tow ya to the meet

[Spray-Bomb]

Well at least I'd be ride'n with somebody cool... lol

Well it's raining cows outside, so it'll be really fun getting up to the shop in my truck (road goes from thin gravel to dirt)

I think today I'm gonna try and fix my oil leak, but if not then I have a whole list of stuff to fix... lol