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Thread: GM Trailer TPMS

  1. #1
    Left The Driveway Raven8906's Avatar
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    GM Trailer TPMS

    Hi all,

    Just upgraded my tow vehicle for my Momentum 399. I went from a 2015 Denali Dually to a 2020 Denali Dually. I have a TST system with the 6 sensors and booster installed on the Momentum, and the the display in the truck. The new GM trucks had a more advanced trailering app which includes a TPMS that can been seen on the info in the radio display. Now I have found the P/N for the sensors GM (84338125) but I see a note in the product details that its not for 5th wheels. I continued my searching and ran accross the following https://gm-techlink.com/?p=11028 info about the new system.

    The intresrting thing that caught my eye was a commet from an Ed. where he said "Additionally, there is a maximum length the sensor can be from the rear of the truck (axles no more than 23 feet from the rear of the truck) and there should not be any open panels or metal objects between the truck and TTPM sensors."

    There is also a 102 PSI limit on the sensors, and I recall the Max tire inflation on the side of my G rated Westlakes is 110 PSI. not that I run them at the full 110 anyway. However that took me down the path of looking into the diameter of the sensor.
    Size of vave stem bore on factory '18 Momentum 399 wheels. I believe GM (84338125) sensors are .433" diameter I suspect that the higher load rated wheels on the Momentum might be the larger .625" diameter.

    Has anyone sucessfull managed to aquire any sensors that work with a 2020 GMC and a 2018 triple axle Momentum ?
    ~ Chris & Sarah
    2018 Momemtum 399th
    2020 GMC 3500 Denali DRW

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    Setting Up Camp
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    The OEM GM sensors are .452" and the wheels on our 310GK-R are the larger .625. I had a guy in Arizona change the stems on my four OEM units to the larger diameter. I have since located a source for the stems and changed a couple more myself. Problem is that the receiver for the TTPMS is behind the rear license plate and won't reliably pick the trailer sensors. I had to modify a unit that I bought from Ebay with an external antenna in order for it it receive the trailer information correctly. It works as it should now and so do the valve stems.

  3. #3
    Seasoned Camper
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    Also keep top-end PSI of the sensors in mind.
    For our new Solitude with the H-rated Cooper tires, PSI is a whopping 125. I believe I saw posted on a Chevy/GM forum that the OEM sensors top out at 99 PSI, BUT I am not 100% sure as I read it as an off-hand comment somewhere in the last few weeks.
    Rather than mess with the whole issue of valve stem size matching, taking the rig into a tire shop, monitoring issues, booster issues - feels like a lot of work for little payoff of integrated TPMS. I'm going with a screw-on aftermarket system for now.
    Colin & Tracy
    '21 Chevy Silverado 3500HD LTZ/Z71/SRW, Long bed, Anderson UH
    '21 Solitude 310 GK-R

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    Quote Originally Posted by Thunderbolt View Post
    The OEM GM sensors are .452" and the wheels on our 310GK-R are the larger .625. I had a guy in Arizona change the stems on my four OEM units to the larger diameter. I have since located a source for the stems and changed a couple more myself. Problem is that the receiver for the TTPMS is behind the rear license plate and won't reliably pick the trailer sensors. I had to modify a unit that I bought from Ebay with an external antenna in order for it it receive the trailer information correctly. It works as it should now and so do the valve stems.
    Thunderbolt,

    Would you provide information the source you found for the larger diameter valve stems? Also what was your solution for reliably picking up the TPMS signal.

    Thanks
    Jeff and Gale
    Vancouver, WA
    New - 2020 GMC 3500 Duramax
    Old - 2005 GMC 2500 Duramax
    New - 2021 Solitude 310GK
    Old - 2018 Reflections 303 RLS

  5. #5
    Setting Up Camp
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    I bought mine from Ebay but you may find them elsewhere. Search for 31 inc 17-50392 tpms .625. You will need to cut the old one off with a band saw or another device than attach the new one with the screw in the bottom. Not that difficult once you see it. On the method to receive signals reliably see my thread starting off Solution to Chevrolet/GMC tpms under tow vehicles. It has pictures of the modification but in a short version is that GM failed to take into account that mounting the receiver for the tire sensors behind the license plate was a bad idea. It blocks the 433.920 Mhz signal from the sensors. You can run without a license plate or move it somewhere else and probably get them to work but I modified mine with an external antenna. You can find a replacement receiver GM part no. 84458180 again on Ebay and modify it like I did. It is made by Schrader for GM and so are the tire sensors.

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    Quote Originally Posted by JTP303 View Post
    Thunderbolt,

    Would you provide information the source you found for the larger diameter valve stems? Also what was your solution for reliably picking up the TPMS signal.

    Thanks
    Have 4 that I was unable to use on our reflection and website of the company in AZ who modifies them from the following link - https://www.mygrandrv.com/forum/show...-Stems-0-625in. Cant comment on signal issue as our did not had any issue on our last trip out with the system for the first time, but when I was researching this seemed those with 40ft+ trailer was having the signal issue.
    2020 GMC 3500 Denali SRW SB Duramax 4x4
    2021 Reflection 31MB Goosebox 16k

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    Setting Up Camp
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    Yes on the longer RV which means distance to the receiver behind the license plate is longer. Those with reception problems can remove the rear license plate and take a short trip with RV attached to confirm that the sensors actually can be received if signal level is adequate.

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    Just so everyone knows i have a 2022 GMC 2500 and they must have listened they now let you take your max to PSI to 150 i think it was.

  9. #9
    Setting Up Camp
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    Quote Originally Posted by Huskers View Post
    Just so everyone knows i have a 2022 GMC 2500 and they must have listened they now let you take your max to PSI to 150 i think it was.
    Great now if they will fix the issue with the receiver on the TPMS and allow me to tell my truck GPS that I am towing a 5th wheel that is 13'5" high so I don't have to run Copilot on my phone that would be a big improvement.

    Thanks for the reply.
    Terry

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    TPMS Receiver relocation

    I made simple bracket and relocated the receiver below the bumper. The original wiring looms were stretched and worked. I’m pulling 37 ft fifth-wheel and it measures 20 ft from center of rear axle to the truck bumper.

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