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Old 06-28-2012, 08:51 PM
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Re: First gear mystery

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Originally Posted by 77rednecktruck View Post
you can't really read a general article on transmissions and expect it to apply here. Dodge transmissions are retarded and don't really follow any normal rules.

Your Jeep probably shifted into overdrive going up the hill at a slow speed and then finally realized it was in the wrong gear and then downshifted.

If you can't tell, I hate the transmission in my Jeep.
There isn't an automatic made that hasn't pissed me off sometime, especially those GM and Ford POS's.. and those European jokes... The Jeep tranny does alright for a 13 year old design, but when you are trying to understand what is happening, remember that the gear ratio being used doesn't always correlate to what is displayed on the EVIC.

So the torque converter can lock up in any gear? At highway speeds it is about a 200 rpm drop when the converter locks up (V8).
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Old 06-28-2012, 09:34 PM
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Re: First gear mystery

Seems more like 400 rpm to me. In the early daze of lockups (e.g. 1979 THM200) it was just on top gear. Then they found people towing in drive so they made it on the top two gears. Trannys lived cooler and longer.

Later it was found that mpg improved in lockup since the torque converters always had a loss factor so they started bringing lock in ealier and earlier until first has a lockup now. It still disengages at pedal over 50%, about the time you go into PE (power enrichment). Near as I can tell the Pentastar Torque Converter has a stall speed around 1800-2000 rpm (pretty tight) so when under 2k the revs will drop more than at 3k. Since usually under 2k that is where you will feel about a 400 rpm drop.

That tight TC coupled with the TC (traction control) also keeps the V6 from burning any rubber.

Personally never cared for a Roto-Hydramatic or a C6 but a THM400 is OK & never saw a 727 I didn't like. This German thingie seems adequate for the job. I am a little concerned about the torque capacity of the 8 speed with four gearsets but expect the engineers know what they are doing. Do prefer something that has been around for a while though. I value survivors.
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