How to tell if tranny has had the de-tune?

dskater411 · **Posted:** Fri Oct 04, 2013 1:13 am

So I remember reading a while back on the forum (couldn't find the information again) that one way to tell if the transmission had the recall/de-tune done to it was the speed at which the final shift took place. I believe the forum said based on whether it shifted at either 58mph or 63mph it either did or did not have the de-tune. Well for one I dont remember which was which, but even more confusing is that I have found that my speedometer is off by 5mph based on both radar and gps testing, and when the gauge says 63mph I am really only going 58 (stock tires, no mods etc) so I wanted to throw that in there too.
Thanks
Dave

arengant · **Posted:** Fri Oct 04, 2013 2:43 am

Base it on your spedometer not gps. 63 (ish) is detune 58 (ish) is OEM

dirtmover · **Posted:** Fri Oct 04, 2013 8:16 am

This discrepancy is normal. Your odometer is also measuring about 5% on the low side.

naturist · **Posted:** Fri Oct 04, 2013 2:11 pm

The best way to tell would be to ask a dealer to look up your VIN. Mine, for instance, HAS had the F37 torque converter replacement, but the dealer who did it neglected the TCM reflash, so it still shifts at 58.

papaindigo · **Posted:** Fri Oct 04, 2013 2:49 pm

The F-37 consisted of 3 parts - 1) detuning the engine power curve and 2) changing the transmission shift points and 3) checking for torque converter problems and replacing if needed (the only for sure replacement was the early TCs with a plastic part that all died young so to speak). I could be wrong but IIRC all 05s and some 06s came out before the F-37 but some late 06s had the F-37 steps 1 and 2 (3 was not needed as TC replacement was only applicable if driving damage occured) done during manufacture

You would have to have access to a factory or equivalent code reader to determine which ECU coding you have relative to engine detuning. Checking the VIN may or may not help as I know of several vehicles, mine included, that positively had the F-37 "done" but equally positively did not have the transmission shift points changed. The odometer and speedometer can be off +-5% either way and independent of each other. If you have access to a GPS find a flat stretch of road and on a warm engine run (moderately not flat out) up to just shy of 62 mph. If you feel and see, on the tach, a noticeable drop in engine rpm shortly before 62mph AND at just a hair shy of 62 mph the rpm is about 1,800 your transmission has not been F-37d. However, if at 62 mph the rpm is well above 1,800 and you keep accelerating and then feel that shift the transmission has had the F-37 performed.

GDE can take care of that but you need to send in your TCM to be programmed.

arengant · **Posted:** Fri Oct 04, 2013 9:06 pm

papaindigo wrote:

The F-37 consisted of 3 parts - 1) detuning the engine power curve and 2) changing the transmission shift points and 3) checking for torque converter problems and replacing if needed (the only for sure replacement was the early TCs with a plastic part that all died young so to speak). I could be wrong but IIRC all 05s and some 06s came out before the F-37 but some late 06s had the F-37 steps 1 and 2 (3 was not needed as TC replacement was only applicable if driving damage occured) done during manufacture

You would have to have access to a factory or equivalent code reader to determine which ECU coding you have relative to engine detuning. Checking the VIN may or may not help as I know of several vehicles, mine included, that positively had the F-37 "done" but equally positively did not have the transmission shift points changed. The odometer and speedometer can be off +-5% either way and independent of each other. If you have access to a GPS find a flat stretch of road and on a warm engine run (moderately not flat out) up to just shy of 62 mph. If you feel and see, on the tach, a noticeable drop in engine rpm shortly before 62mph AND at just a hair shy of 62 mph the rpm is about 1,800 your transmission has not been F-37d. However, if at 62 mph the rpm is well above 1,800 and you keep accelerating and then feel that shift the transmission has had the F-37 performed.

GDE can take care of that but you need to send in your TCM to be programmed.

I thought the shift points happen at SPEEDO measured points, not actual (GPS) speeds. Regardless of actually speed (i.e. different tire sizing) the transmission will shift at the set points based on speedometer. This is based on my specific vehicle only.

papaindigo · **Posted:** Sat Oct 05, 2013 8:58 am

Speedo points as opposed to rpm points I don't know. My speedo is essentially dead on compared to GPS and stoutdog's was pretty close. I do know that 62mph on my CRD without the tranny part of the F-37 was 1800rpm and on stoutdog's with F-37 the rpm at that speed was much higher unless he ran the speed up enough to make the "final" shift and then dropped back to 62mph. We both now have GDE's tranny tune so it no longer matters

arengant · **Posted:** Sat Oct 05, 2013 1:25 pm

papaindigo wrote:

Speedo points as opposed to rpm points I don't know. My speedo is essentially dead on compared to GPS and stoutdog's was pretty close. I do know that 62mph on my CRD without the tranny part of the F-37 was 1800rpm and on stoutdog's with F-37 the rpm at that speed was much higher unless he ran the speed up enough to make the "final" shift and then dropped back to 62mph. We both now have GDE's tranny tune so it no longer matters

With my GDE Trans-tune and taller tires, my transmission shifts at the specified MPH (4th gear at 45, 5th at 55 on speedometer) but I am actually going 10% faster according to GPS. But I am getting off topic...

How to tell if tranny has had the de-tune?

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