Geo Pro g14fk...2919 GVWR.....Should I still tow only in 3rd?

c good

Original poster
Member
Dec 8, 2011
526
I know it's best to stay out of overdrive while towing with our platform. Should I still keep it out of overdrive? I have a external transmission installed from PCM4Less.
 

Reprise

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Jul 22, 2015
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Congrats on the acquisition!

We know that:
Shifting back & forth into / out of OD creates heat, especially in the torque converter.
Excess heat is harmful.

I don't know where you're towing to / from, but even with a lighter trailer such as yours, unless you're on very flat terrain, I would keep it in 3rd, vs OD. It'll put a small hit on your fuel mileage, but that goes out the window anyway when towing something like an RV trailer, as it's basically a big 'sail' that you're overcoming wind resistance with; as speed increases, so does the effect. If you break 9mpg, you're doing very, very well.

You can try OD, if you're on a flat stretch & a wide open interstate, but definitely hook up a trans temp gauge (you can do this via the $5 Torque Pro or Car Gauge Pro apps on a smartphone and an inexpensive OBD-II reader (threads abound on this, so it shouldn't be too hard to find).
Once you cross 200F, keep a closer eye on it, especially if the trans is downshifting a lot. At 230F and up, you're in the danger zone, and susceptible to thermal runaway. At 250F, PULL OVER and wait until you're back below 200F again to continue. At 270F, you've likely burned the fluid and damaged the trans.

Higher ambient temps will contribute to the heat factor as well; they'll climb faster when it's really hot outside.

If pulling a longer grade, don't baby the engine if it downshifts into 2nd. Let it eat a bit (at least to 4000, maybe 4500). Again, shifting back & forth increases heat. If it wants / needs to be in 2nd... consider downshifting to '2'. Yes, it will limit your speed.

The cooler will help you, but that's really a minimum prerequisite for towing, even though you have a lighter trailer. I'd probably put in a 20,000 BTU-rated cooler (or better) for a load like that with your truck, especially in summer temps.

And from your other thread, asking about a TBC... probably the best-known name is Tekonsha. With 2000lb on a single-axle trailer, you probably don't need to go with the big-dog Prodigy T3; something like a Primus / T2 would probably be fine. There's a 4-lead pre-wired harness under the knee bolster area that will accommodate wiring from a TBC; you'll find it near the fuse box by the LH kick panel. Note that the wire colors don't correspond to Tekonshas, so don't just hook 'red <-> red', etc. Look up the colors on both (if you're lucky, the 4-lead will still be taped together with a label indicating the colors / functions.

One last thing... I looked up your floor plan (figuring that the 'fk' meant 'front kitchen'). Since your bath is up front, take a look at the location of your black / grey tanks. If they're located up front, vs. more mid-ships or in back, be aware of the potential for sway. A good WDH will have anti-sway, and that helps. But if you notice the 'tail' of the trailer starting to 'wag' at higher speed... coast down until you can get the tail back under control.

Hopefully, I haven't frightened you too much with all of this. Just things to 'be aware of', especially if you're a novice to RV'ing. Happy Camping! 🏕️
 
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Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
I know when I tow my aluminum ~1000# sled trailer with the TB, even with just one 700# sled loaded (so let's say 2000# total), it tends to hunt between 3rd and 4th gears at 100 km/h (60 mph) so I just leave it in 3rd. No heat issues in winter but the extra wear on the clutches is on my mind. Just like @Reprise said, it's a giant sail so wind resistance is the issue. Might be different if I had 3.73 gears though.

Look at it this way, you're towing a trailer so fuel efficiency is out the window in any case.
 

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