350 turbo trans shifts into 2ed while in low?

Question

why is this haponing

say i stop put it into low and take off it shifts to 2ed with out me shifting it when i put the
shifter in second it does nothing basicley shifting to drive is the only thing that makes it shift aney differentley there is no difference beteen 1@2 shifter possions

Answer 1

Having rebuilt a number of TH-350's, I can tell you about the only thing causing it to shift to second from low is a mis-adjusted shift cable/linkage. To correct this, raise the car onto jackstands and block the wheels. With the key on and engine OFF, put the transmission in low. Loosen the bolt where the cable or linkage attaches to the transmission and make sure the transmission securely clicks into low. Make sure the shifter is still in low, and retighten the linkage.

For everyone out there that says it shifts by design to protect the engine or because it is idiot proof, I say B.S. By design, the transmission should not shift to a higher gear than it is set to. There is nothing electronic that senses engine RPM's that connects to the transmission, and the valve body in the transmission is strictly mechanical, and only works for the gear selected, regardless of engine speed. They stopped using the TH-350 in favor of the TH-700R4, all those cars and trucks have a distributor, whether points or HEI, (they didn't go to coil packs until well after TH-350 stopped production) and the RPM's were usually limited around 5500 to 6000 (also by design) The TH350 is more than strong enough to take the abuse of high RPM's.

The Modulator controls shifting, but it controls when it shifts in relation to engine speed. It operates from manifold vacuum , it allows the transmission to upshift based on a specific amount of vacuum, but again, never higher than the gear selected. Low vacuum or a broken or disconnected vacuum line will delay shifting, because the modulator needs a vacuum signal to operate. It only allow the transmission to shift to the highest gear selected, not beyond. If it goes bad, it usually won't allow the transmission to engage at all. Most new replacement modulators are adjustable since running a radical cam decreases engine vacuum, adjusting it will compensate for the lower vacuum.

The cable guess78624 refers to is the throttle kickdown (also sometimes referred to as the passing gear), which when in drive and you press the gas pedal hard, causes the transmission to downshift, maximizing the engine RPM's and torque curve to give you a burst of power, and a substantial increase in speed. It does not affect the transmission shifting up at higher RPM's, but down, from drive to 2nd, or from 2nd to low, but should NEVER drop from drive to low.

Answer 2

I see that you have some really bad answers!!! I have worked in a transmission shop many years, and have worked on more of these transmissions than probably anyone on here. Some of the answers are on the money though. Your problem is what is called a TV cable. It runs from the transmission to the throttle linkage arm on the carburetor or throttle body. You need to unhook it from where it attaches to the part that pulls the cable. Don't take it out of the bracket that holds it in place. Hold the linkage arm with one hand and push the blck tip of the cable forward away from the way it pulls, and it should pop right off. Now, get a hold on the cable, and pull it in the direction the arm would pull it. you should be able to feel it working something in the transmission, and it should spring back as you release it. If it won't do this, it could be off inside the transmission, and you will have to pull the pan off to get it hooked back to where it goes. Where it attaches to the transmission, use a 7/16" wrench to take the one bolt out that holds it in the transmission. If it is hooked you can see it, if not you will definitely have to remove the pan. Be carefull to not break this part, and it pulls straight out of the trans. It has an O-Ring around it, but when you put it back, wipe all clean and use some silicon on it to make sure it don't leak. Once you are sure it is attached inside the transmission, and you can pull on the cable, and feel it working the valve inside the transmission, you are ready to adjust it. Attach it back to the arm, and go to a transmission shop and have them adjust it, or try to do it yourself. Where the Cable Housing attaches to the bracket is a lock. You can use a small screwdriver to unlock it and the cable will make a snaping noise. Have a friend hold the accelerator all the way to the floor, and push the silver looking lock back into place. This should fix the problem. If you have never done this, you really should go to someone who has, because it is not easy to do. Some of them you unlock, let it relax, lock it back, and stomp the accelerator pedal to the foor, and you will feel it adjust itself. You may also want to check your vacuum hose to the modulator, and where it hooks to the intake to make sure it isn't leaking vacuum. Also; while you are under the car, pull the hose off the modulator, and if any fluid runs out of the hose, the modulator is going bad and needs replaced. If it is bad it MUST be replace with one that has the same color stripe around it, in order for it to work right. There is nothing electronic doing this, and it is the cable causing the problem!

Answer 3

How old is the car? I know the older ones have a "sensor cable" (also called modulator cable) that hooks up the the throttle pivot on carbureter (or fuel injection in same "place") if this breaks, - the transmission thinks you have let your foot off the "throttle", - so it shifts up to "economize" the fuel flow! Even older ones have a vacuum modulator capsule down on the rear lower part of the transmission case,- it does basically the same as the cable on "newer transmissions" however it senses vacuum from manifold to tell it when to shift,,,,,,,,,,,, shifting "up" when vacuum goes below a piont (hence bad modulator, - or bad supply hose-will make it shift up too soon!)

Answer 4

T350s T400s And T700S all do it. Only in first in second it will blow up before it shifts. There are kits to fix it if it is too early for you. Try B&M TCI or TransGo is the best.

Answer 5

you need to readjust linkage or cable because the transmission isnt going all the way into Low (1)It is not equipped with any device to save your engine. when manually put in low it should stay there until you shift it!!!

Answer 6

OIL ive had the same problem 350 th b&m shift kit 10"torque

Answer 7

This is happening because the trany is stupid proof.

If you pull down into man low while driving at a higher speed than what the engineers wanted you to be at for that gear it will wait till you reach a safe speed to engage that lower gear.

and thus if you exceed that speed while in man low it will upshift as built in IDIOT DEFENSE SYSTEM.

Answer 8

Sounds like your shift linkage could use some adjusting.

Answer 9

Are ya taking it to the RED LINE? It and the 400 will shift to keep ya from blowing the motor

Answer 10

because if your rpms are too high and you have manually shifted into first, the transmission will shift into second to keep the engine from blowing up.