I have a original GDE transmission control module, which uses different shift points to the standard KJ 545RFE (as used on the CRD). GDE used to offer custom TCMs that allow owners to set shift points (up and down) in order to set up the vehicle for their needs. There are at least two versions in fairly wide release in the US, but to my knowledge I have the only GDE TCM in Australia. It was purchased years ago direct from Keith at GDE when I was doing export model development testing for them. It was impossible to flash the TCM, and it had to be swapped with one Keith sent to me. It is a fairly big job to swap the TCM in the CRD because of its location tucked up high on the firewall behind the AC canister, stuff needs to be moved, including the cable housing on the firewall.
I wanted the GDE TCM because the darn stock unit would hunt back and forth around 80kph, it simply was never in the right gear it seemed. And towing with it was a nightmare. The GDE TCM tune allowed lugging the engine down to well below 1500rpm in 5th and it would pull away from there without downshifting if you did so gently. It would also shift from 4th to 5th earlier than the stock setup, so there was no need to race up to a high speed up to force the shift and then back down to where you wanted to cruise. I should point out that this was "lock to lock" shifting, meaning the torque converter was locked up Something not possible under stock TCM tunes). I found that my fuel economy improved significantly on long trips, especially when towing my camper, although running the GDE full torque ECM tune also played a role there, as I had significantly more torque available. I don't know if GDE still is in the business of TCM tuning, must check on that.
BTW, fuel economy, highway not towing, with 255/70r16s (on 16x8" rims) was 6L/ 100kms. Abit more with 245/70s On stock rims.
Edit. Just checked, GDE still shows TCM swaps on its website, the first one listed below most closely resembles the programming in my custom unit, here:
https://www.greendieselengineering.c.../-/2_13.action
https://www.greendieselengineering.c...une/2_9.action
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