mike623

I have searched around on here and haven't seen this covered yet so i thought I would ask. Can you adjust the modulator on th350 to make it shift harder? My dad told me back when he had his 71 CS that he adjusted some screw or something, then he could bark 2nd gear. He did say later that it quit shifting right and he had to manually sift every gear. Just wanted to see if anyone here had ever done that or knew anything about it?

TripDeuces

I remember there is a screw inside the nipple where the vacuum line attaches to. Turning it does effect the shift but I never did so I can't comment fully on this. I used to have a Dial-a-Shift from B&M (actually still have it). From what I could tell it was nothing more then a controlled vacuum leak to the modulator. The higher the setting the more vacuum leak and the tranny would shift harder and at a higher rpm. I always thought one on those cheap brass valves from a pet store for aquariums would have worked just as well, hehe. Cheaper too.
But I digress. To answer your question yes it effects it. It should be a small common screwdriver to get at it. Just pop off the vacuum line to the modulator and you can access it.

oldsconv

I believe all the factory modulators that were large size (like a beer can diameter), had a set screw that was adjusted at the factory and then spot welded, so no adjustment. If the tranny was rebuilt or the modulator changed, it probably has the small can size (Like a D Cell battery but shorter) which is adjustable. The set screw is inside the nipple like the previous poster said - pull the vacuum hose off to access. If you still have the original modulator, it is easy to buy the new style and swap it out.

Be careful as you can increase the shift point, but it gets pretty harsh. I think the factory varied the shift point with the modulator but also modified the governor weights as well. I think you can also do this your self if you buy a new governor (4 bolts holds it in side of tranny)

BlackGold

I won't claim that the vacuum modulator has NO effect on WOT shifts (I'm not a tranny expert), but I do know that the purpose of the vacuum modulator is to control part-throttle shifts. Vacuum goes to almost zero at WOT, so I wouldn't expect the modulator to have much effect. The WOT shift points are controlled by the governor.

I assume it's WOT shifts you care about. You don't want your part-throttle shifts to snap your neck, do you?

mike623

Thanks for the replies. To answer your question Black Gold, no I do not want part-throttle shifts snapping my neck. I will have to do some experimenting with it I guess. I normally shift through the gears when I am playing around in the car anyways.
Another question, I might not be hitting the sweet spot when I am going from 1st to 2nd gear but in my 73 Cutlass Supreme I had in high school when pulled down to 1st and took off and hit 2nd I could chirp the tires. My 73 Cutlass Supreme was stock 350 w/4 barrel / stock th350. I have not been able to do it with my 70 Cutlass Supreme with stock 350 w/2 barrel / stock th350 or my 72 Cutlass S with 350 w/4barrel / stock th350. I just rebuilt my 72 engine a few months ago. Is there a trick to this or what?

Yellowstatue

The trick is to replace your radials with cheap bias ply tires like you had in high school and you can chirp all morning

Bluevista

The modulator adjustment won't do much.
Install a shift kit and it should get rubber when it hits second, maybe when it hits third too if you keep it floored.
My GTO's T-400 has a shift kit and the tires chirp when it shifts to second and third without even getting on it hard, burns rubber and fishtails when it hits second if you stay on it.

matt69olds

Turning the screw in the modulator will change part throttle shift points, put only 2-3 mph. To change the WOT shift points you need to change the weights and/or springs in the governor. B&M sells a governor calibration kit. I think its around $40. Be prepared to remove the gov several times to get it where you want it. Trans-go or B&M make good shift kits. If you have a aftermarket converter, use the B&M kit. Its cheaper and works better with high stall converters. The Trans-go kit retains the accumulator functions so they shift softer. I prefer a firm shift. Just my opinion.

jpc647

This is really good to know. I feel like sometimes I've got to give my car too much pedal to get it to downshift, especially on a corner, so maybe a 1/4 turn or 1/2 on this will be enough.

Figured it'd bump the old thread, instead of starting a new one!

lemoldsnut

a th350 has a cable that controls kick down, you may need to adjust it.

rjohnson442

I'll have to find it but there is a pdf file somewhere on the interwebs showing how to trim the weights in the governor to get a later WOT shift point. It shows where and how much to take off to get a specific RPM shift point. I do remember it saying though to practice on a used one first to play around with. Remember you can always take more off but you can't put it back on. In the end I ended up using the pull a part one and left the original one alone.

jpc647

Got any more information on how to do this?

Octania

Service manual has such info.
varies a bit over the years
if the cable goes to the gas pedal, there is a slip fit clamp on the cable end, you install it too far down, then depress pedal all the way and it gets slipped to the proper position. Voila.


So, where is the upper end of your cable?