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Replace old transmissions by attrition.

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The truck headshed tells us that there have been a lot of questions from the field about the 4L80E HMMWV transmission and transmission control module (TCM) E-PROM (or erasable programmable read-only memory). Maybe that's because the HMMWV once had 13 different transmissions with 13 different TCM E-PROMs for each one. Thankfully, things have changed! Now there are only two transmissions and two TCM E-PROMs.

Note that the two TCMs are not interchangeable, so the legacy TCM will only work with legacy transmissions. And the up-armored TCM will only work with up-armored transmissions. Mixing the two will cause the transmission to go into a "SAFE" mode and it won't shift out of second gear.

FED LOG shows that older two-piece E-PROMs (microcircuits) are still available until the supply runs out. They are only compatible with their respective production year.

The HMMWV parts manuals will be updated with this info. Here's what you need to know in the meantime:

All legacy A2/R1 "heavy variant" HMMWV transmissions are being replaced through attrition. So when it's time for a new one, you'll get a transmission, NSN 2520-01-489-0849, and TCM (containing the single-unit E-PROM), NSN 2520-01-579-1379.

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All up-armored HMMWV transmissions will also be replaced by attrition. So you will receive a transmission, NSN 2520-01-489-0850, and TCM (containing the single-unit E-PROM), NSN 2520-01579-2302.
Year Transmission NSN 2520-01- E-PROM 5962-01- Kit

1995 399-4691 430-0182 N/A
1996 430-5291 430-0208 57K3502
1997 439-6830 440-0368 57K3523
1998 461-7072 470-4619 57K3539
1999 461-7074 476-7772 57K3549
2000 473-7410 480-5247 57K3558
2001 489-0849 497-1611 57K3569


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Year Transmission NSN 2520-01- E-PROM 5962-01- Kit

1996 430-2765 431-5121 57K3523
1997 439-6831 440-0369 57K3522
1998 459-8531 470-4621 57K3540
1999 461-7077 480-5246 57K3548
2000 475-1083 480-5248 57K3559
2001 489-0850 497-2519 57K4408
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Title Annotation:HMMWV ...
Publication:PS, the Preventive Maintenance Monthly
Date:Jan 1, 2012
Words:293
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