Low RPM Shifts?
 

At WOT my car only shifts at like 4000 RPMS. I know it's not the tach because my friend's stock 350 beat me :mad: Any ideas or suggestions? Thanks

Install lighter inner weights in the governor.
Either make yours lighter by grinding them or get a b&m governor calibration kit from summit or jegs.

Try adjusting your kick down cable by making it a bit tighter and see if that helps, before you go messing with the govoner weights.

I thought that the kickdown is bypassed when at WOT. Is it not?

I thought we were talking about a 700r4, but i just noticed you have a turbo 350. If your vaccuum is good all you need to do is get an adjustable modulator, and adjust it till you get your shift timing right.

To raise the WOT shift points on a 350 you will need to modify the Governor, just like with a 700. The Modulator does not change WOT shift points.

what does WOT mean???:D

Wide Open Throttle

The modulator will affect WOT shifts, if not adjusted properly. You can gain some rpms by adjusting the modulator, yeah maybe you won't gain 2,000 rpms, but your not in a 4 cylinder your in a v8. I'm just trying to give you an easy adjustment, you may just not have your modulator dialed in.

How could it? There's no vacuum at WOT.

I am not trying to pick a fight here but trust me on this, if you want to change WOT shift point go to the Governor not the Modulator.

I was discussing this today with some guys and i'll explain it to you now. What happens when your vacuum modulator isn't plugged in? Your car won't shift, because it's recieving no vacuum signal. Try it you may be able to get it into 2nd, but no matter how fast you get going you'll never get a turbo 350 into 3rd gear without the vacuum modulator hooked up. Yes you have no vacuum at wide open throttle when you first nail it, but once you start picking up rpms your going to gain some vacuum otherwise your car wouldn't shift. If you don't believe me pull your vacuum modulator off and see how late it shifts then. Just try this turn your vacuum modulator in two full turns and watch it's going to shift a lot earlier even at WOT. Now back it out 4 turns, it's going to shift later, (I might be backwards with the direction of turning it). I've just heard complaints after govonor weigts were shaved, you get complaints like it kicks down way to easily. Have you tried manually shifting it? Bottom line your car needs some sort of vacuum signal to shift.

I guess you've never seen a B&M Transpak, it has a plug to go in place of the modulator, this is optional without changing any other parts, this is also like disconnecting the modulator. It then relies on governor signal to shift. They wouldn't sell that (maybe they would) if it didn't let the trans upshift.

No, I've driven a TH350 equipped car with the vacuum modulator disconnected. As long as the gears are deep enough it shifts into 2nd and 3rd just fine at redline.

Apeiron quote:
No, I've driven a TH350 equipped car with the vacuum modulator disconnected. As long as the gears are deep enough it shifts into 2nd and 3rd just fine at redline.


Doesn't that prove my point, that the modulator has an effect on when the transmission shifts.

Jay727: Why would B&M make anything for that matter, they just do, do their products work, that depends on what you consider working.

Only at part throttle. With the modulator disconnected the transmission thinks it's at WOT all the time and shifts accordingly. Shifts happen at the same time with the same firmness with the modulator disconnected as they do at WOT.

Well put Apeiron.

That is a completly untrue statement. There is vacuum at wide open throttle once the rpms start picking up, and no the car doesn't shift the same with the vacuum modulator disconnected, I don't know who told you that and i've never seen a car act the same with the vacuum modulator disconnected. You must have a bad modulator on your car or something. Just try it if you don't believe me pull your modultor off, put it in drive it won't evevn want to automatically shift you'll have to manually shift it and even then they usually won't go into third gear.
Look in the diagnose charts. You know what it says under car won't shift No vacuum signal vacuum modulator disconnected etc etc....

It's possible to have a little vacuum at hi-rpm's (maybe an 1" of vacuum), this though will have no effect on the WOT shift points. If you start to pull more than a couple of inches of vacuum (at WOT), then it might have some effect. If you get kickdown to easy (TH350), then adjust the kickdown cable accordingly. Depending on which model TH350 you have, they have different rate detent springs which effect WOT shifts (it works with the governor to determine WOT shift points).

I have a turbo 350 in my car with no modularor line and i have to manually shift it all the time...It will NOT shift automatically

That's because it has a manual valve body, the modulator was disconnected because it's not needed with a manual valve body.

For the record, I have a th350 and it'll shift with no vacuum line. It shifts with no vacuum line at a little higher rpm than it shifts at wot with the vacuum line.

Oh yea...Forgot about that...

I'm not meaning to come off as a know it all, I'm just telling you guys my experience and giving you some input. I've been building transmission for a year now, and my mentor has been doing it for 20 years and this is my year of experience and his 20 years of experience. I just had a truck come in the other day and they were complaining that it wouldn't shift, turns out the vacuum modulator was unplugged plugged it back in everything was fine. When were done rebuilding a transmission if the shift points aren't right we adjust the modulator accordingly and have never had a problem getting the proper shift timing. If your having a problem with your car shifting too early you first you try to fix the problem. You would only shave the govonor wieghts if everything was operating correctly and you still didn't have the right shift speed. By adjusting the modulator what your doing is tricking it to think it has more or less vacuum than it's actually getting, therfore say your getting 15 inches of vacuum and you loosen the tension on the daiprham it will fool your modulator into thinking it's getting more than 15 inches of vacuum, tightening the tension will make it think it's getting less vacuum than it actually is. I haven't hooked up a vacuum gauge up yet to see exactly what the vacuum will be at WOT once the rpms start picking up, but James says it will be somewhere around 7 inches once you get up in the rpm band, and 0 inches right when you jam that throttle. If someone has hooked up a vaccuum gauge to see exactly what that vacuum is cruising down the road holding it wide open throttle please let me know, cuz i'm curious to know if it is incorrect that the vacuum won't start increasing as the rpms increase under a WOT condition, then maybe that will answer everyones questions.

My vacuum gauge reads pretty much zero at WOT even at 6000 RPM on my 385. Think about carburetor flow numbers. Four barrel carbs are rated at 1.5 inHg. A 750 CFM carburetor will have 750 CFM flowing through it when there's 1.5 inHg of vacuum in the manifold. My 385 cubic inch car wants about 668 CFM at 6000 RPM, so with a 750 CFM carb there'll never be enough demand even to get 1.5 inHg of vacuum.

Your customer said it wouldn't shift because he knew something was wrong, it's not typical for the average person to go out an redline their vehicle just to try and get it to shift, if he did it probably would have shifted.

I know neither one of my vehicles has vacuum at wot, I regularly use a vacuum gauge with a 6' hose on it and put it in the car so I can see it, I use this procedure to tune power valves in holley carbs. An engine can have vacuum at wot if the carb is too small.

Back to the governor issue, What if you go from a 2.41 rear gear ratio and put in a 4.11?
You have to fool the governor into thinking nothing has changed so you install lighter weights because before with the 2.41's it was turning 1869 rpm's at 60 mph and now with the 4.11's it's turning 3187 rpm's. The transmission will shift way too early with just the gear change. Because of the centrifugal force on the governor, centrifugal force will have less of an effect on lighter weights.
I'm surprised you don't know this being a trans builder.
Next time you get to experiment with a th350 do this, Put a "C" governor out of a 700 in it and disconnect the modulator, it'll upshift.

Keep in mind that all cars are different and are going to have different vacuum readings at cruise and at wot.

You don't have to get rude, I'm not denying that changing the wieghts on the govonor will change the shift point, i'm just telling you i've experienced higher shift points after tuning the modulator even at WOT. You guys keep throwing different scenarios in here like the rear end gears are changed, but all I said was it's possible to change WOT shift speed by adjusting the modulator and i've done it many times. I even asked the transmission instructor at my school he agreeed with me. In practice you wouldn't go and grind the govonor wieghts unless adjusting the modulator didn't get you there.
If you want to prove your point to me explain this. After removing the vacuum line to the modulator I drove down the road in drive and revved the piss out of it, now i got second, but no matter how fast I went I never got that thing into 3rd gear. The car had third just fine with the modulator plugged in.

I wasn't trying to be rude so I'm sorry about that.
I think one thing has been left out of all these replies to this and that is the modulator spring force. It seems if the modulator is disconnected you could still adjust the wot shift points by the screw because it would change the modulator spring force. (not that anyone would do that but for the sake of discussion). So that may prove your point. That may also be why you never got into third. OR it may have went to third if you took it up to 90 mph, I don't know.

I'm not sure how you do your work, like take a trans out, rebuild it and put it back in the same vehicle (not all shops do it like that) This would eliminate a lot of guess work.
On the other hand I am not a trans builder, I get my transmissions from who knows what and when it goes into a custom built car with non stock gears, tires, converter, engine, etc. I have to start from square one to tune it to get the desired shift points and timing. I usually start with the modulator and then go to the governor. I guess I'm just stuck on my old ways.

Lets squash this discussion, because we've beat this to death, but hopefully we've all learned a little something. Please don't think I was arguing with you guys this was just a mere discussion, so I hope no one has any hard feelings. I'm a young guy so i'm easily pursuaded to except other points of views, all though i'm a little stubborn at times. I'm just hear to give you guys my opinion.