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Automatic Transmission Cooling


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Is it true that our auto transmissions don't reach full cooling capacity until lockup in 4th gear? I have not got my Posi-lock installed yet and I doing a tow with my travel trailer this weekend. So when going up a paved steep road that would normally be in second gear for a few miles. Should I disconnect the vacuum line and run in 2 wheel drive low range in 4th or 5th gear for optimum cooling of transmission? I don't have a Trans temp gauge yet to monitor.

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They will stay the coolest when in lock up, and will generate a lot more heat in fluid coupling. As far as running in 2 low, depends on how fast your driving. Any faster than 25 or 30 mph and I think I would stay on the high side. I have done it before but it was also a secondary road (if you could call it that) in poor condition and I probably averaged no more than 20 mph. It doesnt take much to really wind em up on the low side. How big is your trailer, and what kind of grade are you climbing?

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Have no trouble finding overdrive (5th gear).

- - - Updated - - -

Have no trouble finding overdrive (5th gear).

You are probably feeling the converter lockup. You don't have 5 gears. The converter will lock up creating less slip when it goes from hydraulic turbine torque multiplication to mechanical lockup.
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I have 1,2,3, lock up and overdrive. Effectively 5 speed transmission. :moon: Am I the only one who can feel my truck to through 5 shift points?

well. you feel it locking the TC then shifting, then locking again. at or around 40-46 mph you go into OD, then your TC will lock. on the right grade you can get 1-2-3-tc lock- OD tc unlocked, then TC locked. the shift points your feeling the is the TC locking and unlocking as it goeds htrough the gears.
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Is it true that our auto transmissions don't reach full cooling capacity until lockup in 4th gear? I have not got my Posi-lock installed yet and I doing a tow with my travel trailer this weekend. So when going up a paved steep road that would normally be in second gear for a few miles. Should I disconnect the vacuum line and run in 2 wheel drive low range in 4th or 5th gear for optimum cooling of transmission? I don't have a Trans temp gauge yet to monitor.

I dunno how much your trailer weighs, but I highly doubt it is as much as mine. I don't think you will have any problems puling it as I don't with mine...
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Any time your not locked up your going to create heat and have higher temps .... Worse in slow speeds as you get no airflow over the tranny cooler. Not much you can do about it apart from get a guage and drive normal .... It normally takes a lot of start and stop traffic in very high ambients for it to be a problem .... A short spike in temps isn't going to hurt

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:doh: :cry:I promise you are not feeling a 5th gear. I know exactly what you are referring to, and that is lockup, NOT an extra gear. It comes from the factory as a 4 speed, and no how no way is the best builder ever going to squeeze an extra gear in a case thats designed as a 4 speed. Next time you drive your truck, listen and feel for it. The 1,2,3, shifts should be very definitive. Then, when it goes into lockup (not 4th) it will almost feel like a half gear. Then from lock up it will go right to lock up in 4th UNLESS you are on a steep grade or pulling heavy, then it will go from 3rd lockup to 4th, then lockup. So essentially you can feel the trans shift as many as 6 times, but will only shift gears 4. I hope that helps, it is the best my simple mind can describe it.
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I don't understand why you guys are focused on the number of mechanical gears are in my transmission? I have a twin disc billet t/c and my lock up is as solid as the 1,2,3 shifts. Then there is overdrive. I tried to upload a video to YouTube but wouldn't load. Maybe it will from home with wifi. Sorry if the rest if you have a whimpy lockup. :banghead:

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The reason for the discussion on the lock up is to distinguish the difference between the trans shifting into lock up and shifting into another gear. They are not the same. I've ridden in a truck with a 6k dollar Suncoast trans/twin disc convertor and my 3000 dollar Dean Bower special with a single holds every bit as well.

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I don't understand why you guys are focused on the number of mechanical gears are in my transmission? I have a twin disc billet t/c and my lock up is as solid as the 1,2,3 shifts. Then there is overdrive. I tried to upload a video to YouTube but wouldn't load. Maybe it will from home with wifi. Sorry if the rest if you have a whimpy lockup. :banghead:

It's a tone thing. This isn't some random truck forum. This is a community of sick, sick, people. We are on the run from sanity, and we take our trucks seriously. We discuss minutia, we revel in ISX and his 12V madness, mopar man in his amazing wood cutting skills... And then, it all circles around our devotion to decade old or older trucks that really weren't intended to be on this earth this long anyway! These trucks are near and dear to our... sigh. Aw, hell. I digress. As I step off my soapbox... Let me summarize: Al Gore (inventor of the internet) once said in his leading role in the original Tron movie, "the internet is serious business!" :ahhh: I think I even have a photo of him saying it below. post-11098-138698204972_thumb.png
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