I've got a question that I think I saw addressed here way back when, but at that time I didn't need to know the answer, so I didn't pay attention. I've now got a 97 PSD F250 with the ZF 5spd and a 3.55 LS rear end. It seems as if there's been a lot of debate about whether or not you should tow in OD (5th). I pull a 25ft travel trailer occasionally, mostly on the interstates, and haven't YET been into any serious hills with it. The trailer placard SAYS it weighs 6,000lbs, although I know I can't necessarily trust that. Haven't had it weighed yet. Anyway, when I pull it in 4th, I'm really winding the engine RPMs up by the time I'm up to about 55 or 60mph. I've put 'er in 5th, and to be honest, the truck hardly seems to know the trailer's back there. RPMs on the engine are about what they would be unloaded, it barely backs off on hills, etc. etc. My question is whether long-term pulling of this kind of weight in OD will cost me a transmission. If I pull in 4th, it seems like I'm causing a lot of wear and tear on the motor. If I pull in 5th, I'm afraid I'm tearing up a transmission. Somebody let me know what's right!

Thanks,

rotorhead

 

You should be alright crusing in OD. Trannys have come a long ways in the last few years. IMHO of course.
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John

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One thing to look out for when towing in 5th with the ZF tranny is tranny temp.. I have heard that the ZF runs pretty hot when towing and that running in 4th will cool it down because there are less frictional losses in the transmission when running in 4th as compared to 5th. If you want to monitor the tranny temp there is a company that makes a plate that replaces one of your pto plates and has a port for a temperature sender. I believe Fabcraft is the name of the company that makes the plate. If you want to get really serious, I have heard of people using other ports on this plate to add a tranny cooler.