Th350 modulator problems. TH350 Transmission 2019-01-19

Th350 modulator problems Rating: 9,7/10 1148 reviews

What are symptoms of a worn tranny modulator valve?

th350 modulator problems

Connect the Mityvac to the open T and read the vacuum at idle. The valve is made from steel but its housing the shaft is an aluminum casting. The design is elegantly simple - oil pressure acts on one end of the valve while force from the spinning weights ats on the other. You can troubleshoot these symptoms to determine if your car's modulator is faulty. I don't know if it matters or not, but I can hear the solenoid engage if I hit 12+ to it. In my previous article I tried to avoid getting into too much detail in order to avoid confusion but my posting has generated a lot of interest so I'll expand upon the subject a bit. You should not need it, if you need to downshift to get around a car for whatever, you are seriously underpowered, and having a kickdown linkage is the least of your worries.

Next

TH350 Transmission problems with shifting

th350 modulator problems

This can cause the same problems as wear in the valve area. Does it stall or does it stay running ok? One final thought: your original question suggested that the shift speeds are too low at all throttle openings. I'm pretty confident about my new vacuum lines. As engine loads increase, vacuum diminishes, causing the transmission to shift later and more firmly. Have you ever heard a knock or a rattle sound coming from under your bellhousing? Unfortunately, these changes interact and you will need to iterate to get both of them where you want them. Any idea how much vacuum you're pulling? I have also read some about the kickdown not working properly, but mine is not even hooked up right not, is it still a possible problem? I still think the internals might be good since it seems to be shifting now. Every pump is outfitted with new seals and bearings regardless of its condition.


Next

How to Know When Your Modulator Valve Is Bad?

th350 modulator problems

I like the idea of a faulty vaccum line to the modulator though,sounds like a possibility. The guy I bought the tranny from said that it functioned just fine when he pulled it out of the car but now here it is 20yrs. Let the car do its work, your only the pilot, hanging on for dear life. I will replace dipstick and kick down cable o-rings today. As far as adjustments, in my experience I have discovered that with these, when the Swith is out of Pitch, I swap em out for the 350, I have had luck getting ahold of them for cheap. Various symptoms arise when the vacuum modulator diaphragm ruptures or when vacuum leaks develop. Like the race, it is susceptible to cracking and shattering.

Next

Vacuum Modulator Installation GM TH350/TH400 Transmission

th350 modulator problems

The actual breaking point will depend on vehicle weight, gear ratio, traction and driving style. Drive the car on a flat roadway where impeding traffic is not a concern. Engine idle speed does not seem to be excessivly fast as might be caused by a vacuum leak although I have not investigated the modulator or the line yet so I suppose that a leak is possible. I have not made any adjustments on it yet suppose to be factory set. The contamination can get washed out of the governor and end up in the valve body where it will cause bizarre problems. The fluid level is just a slight bit high, it is not burned and there is no slipping that I could detect.

Next

Diagnosing GM Transmissions

th350 modulator problems

Vacuum-operated modulator valves are installed in automobile automatic transmissions for the purpose of controlling shift patterns. As for clutch count, Nusser tells us that the factory supplies either three or four clutches, depending on the year of the transmission. Pull the valve body off and see if any of the valves are stuck. The harshness of the shift is determined solely by engine vacuum; the vacuum modulator is used to sense the vacuum and to change the vacuum signal into a pressure signal inside the tranny. This is usually stems from a low or dirty transmission fluid level. One leg comes from the vacuum pump and the opposite leg goes to the transmission. Supercharged and turbocharged engines making over 1,000 hp on pump gas are the hottest rage right now.


Next

GM Turbo 350 Transmission Rebuild Troubleshooting Guide

th350 modulator problems

The system works as follows: assume that you are idling and then begin to open the throttle. Can someone please explain how these transmissions shift, perhaps outline a procedure for troubleshooting this problem, and possibly offer an opinion as to what might be the most common explanation for my problem? Deffinetly not going to the carb and I'll check the gas pedal at lunch but I've been under the car a few times and half ass remember looking for it and it's just not there. The outermost end of this portion is the place where you remove material. With that in mind, there are a number of internal pieces that should be upgraded for applications transmitting approximately 400 lbs-ft of torque or more through the transmission. In Racing, the driver and car become one. The 3rd gear jumps off to 2rd.

Next

What are symptoms of a worn tranny modulator valve?

th350 modulator problems

This requires a new planetary pinion carrier and ring gear that will accept the needle bearings. Beattie Mark, Scott, and J. From a stand still, if I put it in any gear, first or reverse, the truck will stall out after a couple of seconds. This is the 34-element intermediate sprag found in the Turbo-400, and is usually replaced during a rebuild. This eliminates the potential for a leak at the suction tube or O-ring in the case. It was leaky, but not the primary problem.

Next

TH350 problems

th350 modulator problems

. In the hot rodding community, the transmission can sometimes become a neglected component in the driveline. Do I just remove the vacuum modulator and see what's going on behind it? Last week my son loaded about 2000 lbs into it and drove ten miles. Larry As far as the adjustment, the screw is inside the tube where the vacuum line pushes on the modulator. I'm getting vaccum to modulator valve and line is secure. Small pieces of dirt or debris are the enemy of the automatic transmission as it is a close-tolerance hydraulic system with quite a few moving parts. When this occurs, the input spring is more than likely destroyed, and the only component engaging forward is the overrun clutch, which is totally inadequate to hold engine torque for acceleration.

Next

Chevy automatic transmission workings (Bob Hale)

th350 modulator problems

I plan to check the modulator valve next. I'm thinking my torque converter is locked up. . In almost all cases the valve body must be removed to correct any issues, and this should be done after all other possibilities have been eliminated. I have Park, Reverse, and First. If the valve body is ok, just yank that thing out and go through it, paying close attention to the the intermediate clutch and the intermediate sprag.

Next

Chevy automatic transmission workings (Bob Hale)

th350 modulator problems

The problem with installing a rubber line as opposed to a hard line is that the vacuum and heat from the powertrain will cause the rubber line to collapse, trapping the vacuum at the modulator. First, I need to ask a qualifying question: has the transmission been modified e. The higher this pressure, the more harshly the trans shifts. Nusser says to pay particular attention to the wearable pieces of the front pump and replace anything that shows signs of wear marks. Here's my governor: And here's a video of the last test drive. Alright, I'm back with yet another problem! I noticed that the vacuum line to the modulator was a little rusty but it seemed ok. The rate of clutch engagement is a function of the modulator pressure; low modulator pressure causes slow engagement and a smooth shift.


Next