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newb question about F37
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=49719		 Page 1 of 1
Author:  TennesseeCRD [ Fri Jan 29, 2010 8:51 pm ]
Post subject:  newb question about F37
Ok, I'm still learning so bear with me. I've been reading a few of the older posts about the F37 and kind of understand what it is, as far as shift points and rpm's but why is it bad for us and why did Jeep do it? As I understand it 1700ish rpm's at 60 mph for a non f37 as aposed to 1900ish rpm's for one that has been done. Why is this bad for us?
Steve
Author:  flman [ Fri Jan 29, 2010 9:11 pm ]
Post subject:  Re: newb question about F37
TennesseeCRD wrote:
Ok, I'm still learning so bear with me. I've been reading a few of the older posts about the F37 and kind of understand what it is, as far as shift points and rpm's but why is it bad for us and why did Jeep do it? As I understand it 1700ish rpm's at 60 mph for a non f37 as aposed to 1900ish rpm's for one that has been done. Why is this bad for us?
Steve


It was to stop shudder, and prevent the torque from tearing up torque converters. I am sure the guru's in the forum who study all of this stuff could tell you more. I just like to drive and tinker with oil burners.
Author:  stoutdog [ Fri Jan 29, 2010 9:38 pm ]
Post subject:  Re: newb question about F37
The "bad" is decreased power, delayed shifting, and somewhat lower mpgs... I've driven CRDs with and without the F37, and I must say that the ones without the F37 shift more naturally and get up and going much more quickly :JEEPIN:
Author:  TennesseeCRD [ Fri Jan 29, 2010 9:49 pm ]
Post subject:  Re: newb question about F37
Can't it be re-tuned to non F37 specs?
Author:  ATXKJ [ Fri Jan 29, 2010 9:53 pm ]
Post subject:  Re: newb question about F37
The CRD torque peak from the factory was ~1800 rpm - the original coding on the transmission allowed it to lock up around 1800 - this gave great acceleration - it also killed torque converters.

Chrysler was faced with the option of designing a torque converter that could handle the CRD torque - or detuning the CRD to work with the existing torque converters.
Option 1 required development dollars, Option 2 required a software tweak... I'm sure Management struggled with this decision for at least 1/2 a second and chose Option 2.

now to make it a little less obvious - they didn't actually change the engine (much) - what they did was change the transmission control module to not lock up until the engine revv'ed past the torque peak. Therefore peak engine torque goes into heating tranny oil and not accelerating the Liberty.

(the (much) is about a decrease at the point of shifting - gmctd had a post about defeating that - he put a toggle switch in the wire)

Oh yeah - and the TCM is encrypted as are most control modules - but because of limited production - no one's spent the time to crack it.
Author:  stoutdog [ Fri Jan 29, 2010 11:28 pm ]
Post subject:  Re: newb question about F37
TennesseeCRD wrote:
Can't it be re-tuned to non F37 specs?

As of the moment, no...

*cough* GDE *cough* :jester:
Author:  CATCRD [ Sat Jan 30, 2010 5:46 pm ]
Post subject:  Re: newb question about F37
TennesseeCRD wrote:
Ok, I'm still learning so bear with me. I've been reading a few of the older posts about the F37 and kind of understand what it is, as far as shift points and rpm's but why is it bad for us and why did Jeep do it? As I understand it 1700ish rpm's at 60 mph for a non f37 as aposed to 1900ish rpm's for one that has been done. Why is this bad for us?
Steve



It was a slap in the face, because instead of Jeep admitting a design problem and replacing your failed component with a stronger one, they just gave you software that reduced engine power. It wasn't just a change to shift points.
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