Transmission issue?

[kking08]

Recently bought a 1999 M1097 with the 4L80 transmission and I am having odd shifting issues. Once the vehicle is up to temp and when cruising above 50 mph the trans truck will shudder for a split second. Feels like the torque converter is locking and then unlocking. The issue started occurring every once and while but is now happening more often. Checked for TCM codes but none were present, also checked the TPS and it is plugged in. Only known issue with the truck is a faulty temp gauge but I am waiting for the new sender/gauge to show up. Any clues on what this could be?

 

[TOBASH]

Is the TPS clocked properly? If out of position it can do this.

Also, check the basics… fluid level and filter.

Also make sure brake pedal switch is not screwing things up.

 

[kking08]

Is the TPS clocked properly? If out of position it can do this.

Also, check the basics… fluid level and filter.

Also make sure brake pedal switch is not screwing things up.

Thanks for your help. I checked the fluid and it is red and does not smell burnt. The brake light switch seems to be working properly but is there a test or some way to verify that the TPS is clocked properly and also the brake switch is working correctly?

 

[Mogman]

What you are experiencing is called torque converter shudder.
It sounds like when warmed up it does not have enough pressure to keep the TC locked up and or the TC is worn out.
Have you changed the fluid and filter in the trans? if not that would be the next step, with a close inspection of the sediment in the pan.

 

[Thunderbirds]

What you are experiencing is called torque converter shudder.
It sounds like when warmed up it does not have enough pressure to keep the TC locked up and or the TC is worn out.
Have you changed the fluid and filter in the trans? if not that would be the next step, with a close inspection of the sediment in the pan.

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I've had similar symptoms when I first drove my M1123, 6.5L non-turbo with 4E80E transmission. Some additional steps AFTER you follow Mogman's steps, check the transmission wire harness plug at the transmission, mine had residual transmission fluid in it from an external leak. Disconnected batteries, unplugged connector (J1 if I remember correctly), used electrical cleaner spray liberally, used pressure air to dry it, reconnect. Also inspected and adjusted my throttle position sensor by just a little bit to bring it within tolerance according to the TM. Both these helped me fix my symptoms. I am not sure which of these did, but I recommend both. It has been shifting great and going into TCC lock every time. All these symptoms only showed up once the fluids were at operating temperature.

Good luck.

 

[kking08]

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I've had similar symptoms when I first drove my M1123, 6.5L non-turbo with 4E80E transmission. Some additional steps AFTER you follow Mogman's steps, check the transmission wire harness plug at the transmission, mine had residual transmission fluid in it from an external leak. Disconnected batteries, unplugged connector (J1 if I remember correctly), used electrical cleaner spray liberally, used pressure air to dry it, reconnect. Also inspected and adjusted my throttle position sensor by just a little bit to bring it within tolerance according to the TM. Both these helped me fix my symptoms. I am not sure which of these did, but I recommend both. It has been shifting great and going into TCC lock every time. All these symptoms only showed up once the fluids were at operating temperature.

Good luck.

I am changing the transmission filter/fluid this weekend so we will see what that does. Ive read about adjusting the TPS sensor but it seems you need a scan tool to do it. Were you able to adjust without the tool?

 

[Mogman]

I am changing the transmission filter/fluid this weekend so we will see what that does. Ive read about adjusting the TPS sensor but it seems you need a scan tool to do it. Were you able to adjust without the tool?

Take pictures of the sediment in the pan before you clean it.

 

[Thunderbirds]

I am changing the transmission filter/fluid this weekend so we will see what that does. Ive read about adjusting the TPS sensor but it seems you need a scan tool to do it. Were you able to adju

Yes, you are able to make adjustments just with a digital voltmeter or multimeter. You will be piercing the wires behind the connector. There are certain values for resistance, and also for voltages while you have a 16mm block installed IIRC. You can find the steps and values in the troubleshooting part, and also in the transmission troubleshooting buide. If you don’t have them, let me know, i can look for them( i am away from my laptop at this moment). It would be easier if you had the test cable set, just an extension with access to measure without poking holes in the insulation, but it can be done without.

let me know if you need more help, I should be able to get back in the next day or two.

 

[Mogman]

Yes, you are able to make adjustments just with a digital voltmeter or multimeter. You will be piercing the wires behind the connector. There are certain values for resistance, and also for voltages while you have a 16mm block installed IIRC. You can find the steps and values in the troubleshooting part, and also in the transmission troubleshooting buide. If you don’t have them, let me know, i can look for them( i am away from my laptop at this moment). It would be easier if you had the test cable set, just an extension with access to measure without poking holes in the insulation, but it can be done without.

let me know if you need more help, I should be able to get back in the next day or two.

If it seems to shift normally and you do not have any codes I would be doubtful it is a TPS issue, even if the TPS was causing the TC to lock and unlock it should not shudder, the shudder is the TC clutch slipping, it is actually possible the wrong fluid could cause this.

 

[kking08]

Take pictures of the sediment in the pan before you clean it.

Just an update. I changed the filter/fluid and found no sediment in the pan, fluid still looked good and didn’t smell burn. Also found very minimal residue on the magnet

 

[actionpaintball]

Intermittent brake switch can cause this, experienced it before....TPS as mentioned already is also common. You could wire a TC lockup demand dummy light to where you could see it and see if the lockup demand is going on and off.