Transmission and internal shift mechanism - 2002 Yamaha YZ 426 F

There could be a number of possible reasons why your G30 Chevy van is not shifting out of 1st gear. Some potential causes could include:

1. Faulty shift solenoids: The shift solenoids are responsible for controlling the flow of transmission fluid through the valve body, which in turn affects the shifting of gears. If the solenoids are not functioning properly, it can cause the transmission to get stuck in 1st gear.
2. Low transmission fluid pressure: If the fluid pressure in the transmission is too low, it can prevent the gears from shifting properly.
3. Faulty transmission control module: The transmission control module (TCM) is responsible for controlling the shifting of gears in an automatic transmission. If the TCM is faulty or has malfunctioned, it can cause the transmission to get stuck in 1st gear.
4. Internal transmission issues: There could be internal issues within the transmission itself that are preventing it from shifting out of 1st gear. This could include worn gears or clutches, or other mechanical issues.

It is recommended to take your van to a qualified mechanic or transmission specialist to diagnose the issue and perform any necessary repairs.

You do not say it this is for an automatic or manual shift model.

If an automatic, the first thing I would look for is some problem with the linkage mechanism from the dash shiftier to the transmission. It might be out of adjustment.

This may also suggest a failing speed. The transmission speed sensor is a magnetic sensor that provides this information, allowing the transmission to shift smoothly. The sensor counts the internal number of revolutions of the transmission and transmits that information to the transmission control unit, where the data is used to determine the rotational speed. As the rotation increases, the control unit directs the changing of gears. When this is not working properly, this may cause the transmission to shift erratically or in some cases not at all

If it isn't then the problem is located in the transmission itself, probably a dirty valve body. Not something that can be fixed with out a profession mechanic.

J Transmission Speed Sensor Replacement Service Cost

If your vehicle with a Nitro engine is not upshifting and you're getting a P0750 code, it indicates that there is a problem with the shift solenoid "A". This solenoid is responsible for controlling the hydraulic pressure inside the transmission that helps to activate the clutches and bands that are responsible for shifting gears.
There are a few reasons why the shift solenoid "A" may not be functioning properly, which could lead to the transmission not upshifting. These reasons include:

1. Malfunctioning Shift Solenoid "A": The shift solenoid "A" could be faulty, stuck, or damaged, preventing it from functioning properly.
2. Wiring Issues: There could be issues with the wiring or connections leading to the shift solenoid "A," which could cause it to malfunction.
3. Low Transmission Fluid: If the transmission fluid is low or dirty, it could prevent the shift solenoid "A" from functioning properly, causing the transmission to not upshift.
4. Internal Transmission Problems: There could be internal problems within the transmission, such as a clogged valve body, damaged transmission bands, or worn clutches, which could cause the shift solenoid "A" to malfunction.

It is recommended to take your vehicle to a certified mechanic or dealership to diagnose and repair the issue, as transmission issues can be complex and require specialized knowledge and equipment to fix properly.

Both error codes you have are transmission related. P0736 is an error for reverse has wrong gear ratio. P0700 is a general transmission problem code
http://www.obd-codes.com/p0700
http://www.obd-codes.com/p0736
for more information.

With a scanner you can drive the car and watch the data to see what is missing for transmission shifting. But struck by lighting tells me that POSSIBLY the diodes in the computer have been compromised . or a internal mechanical fault inside the transmission . THEORY the car revs to 3000 and goes into neutral this means the shift has occurred by the next gear is not holding by pressure (that solenoid is not working) or a internal leak or the band servo has applied but the band does not hold

With a scanner this can be tested possible problems are stuck shift solenoids or internal mechanical failure. Most generic scanners do not have the software to test.

code p0730 refers to incorrect gear ratio.==causes --wiring--TR sensors/switch--shift solenoids--transmission mechanical fault
code p0780 refers to gear selection--shift malfunction====causes--wiring--TR sensor---shift solenoids--transmission mechanical fault.. have the shift solenoid checked out. Have a pressure test done on the transmission to check for internal damage.

Follow the shifter reach rod that runs from the shift lever back to a short lever on the transmission. Take the nut off and take the rod loose from this short lever. Then, move the forward like you are going to shift into low gear but don't actually shift the transmission into gear. Feel for the spring tension. Then, move the lever backwards and feel for the spring tension there. Check the shift lever and the reach rod for binding. If you don't feel the spring tension trying to return the lever back to the center, it's likely that the shifter pawl return spring is broken. This spring is what returns the shifter lever back to 'center". But,the temperature of the transmission will not change this. If the spring is broken, it's broken cold or hot. If the spring is good and there is not bind in the linkage, the problem may be in the shifter cam mechanism inside the transmission. Either way, this is an internal issue in the transmission.

Good Luck
steve

are these codes shift solenoid codes because they could be.

Sounds like the mouse chewed more than just your fuel pump wiring. How hard your transmission shifts is controlled by the PCM, controlling the force motor inside the trans. There should be some troublecodes present in the PCM that may help you pinpoint the problem. You can also hook a scanner to your vehicle to see what it is doing.

There could also be internal mechanical or electrical problems with your transmission. A scanner with bi-directional controls can help you determine whether your problem is electrical or mechanical. These transmissions are known to break springs and plastic pistons in the valve body. Also, if your transmission shifts hard in all gears, including shifting into reverse, your sun shell may break. When this happens, you will loose R, 2nd & 4th gears, leaving 1st and 3rd.

As preventive maintenance, installing a shift kit, e.g. SK4L60E from Transgo, and replacing the plastic accumulator pistons with ones made of aluminum may correct your mechanical problems.