Towing

[bennett_taylor]

I have a 00 X, 39k miles, bought new in 99. I just recently bought a 4800lb boat and have been towing it w/ my X. I just towed the boat from Knoxville TN to Indianapolis (385 miles w/ 100 miles of hills). The X did fine, the AT temp light never came on, the truck handled fine, but was underpowered a bit for a boat this size. I was just curious if you all could comment on the life of my truck / transmission doing this kind of towing with it. I feel like I am tearing the crap out of my truck w/ this boat. Also, should I change the oil in the transmission? Differential? Transfer Case? Front Diff? Let me know your opinions and what I should look for. Any how to's would be awesome.

Bennett

[OffroadX]

Most importantly, turn off the overdrive unless you're truly loafing along (level or downhill). You should learn to recognize when the transmission torque converter is in lockup and when it isn't. If it's in lockup, you're golden, but if it's not, you're rapidly building heat in the transmission. Don't trust the A/T temp light unless you're certain it actually works, many have reported that theirs does not light up when the key is first turned on.
Turning off overdrive merely locks out 4th gear. The torque converter is almost impossible to get out of lockup above 50 MPH in third gear, but will unlock at the drop of a hat when you ask for any power in 4th (ovedrive). Experimenting with the O/D Off button is the best way to figure out the difference between 3-locked, 4-unlocked, and 4-locked. If you ask for moderate power in 4th and the RPMs jump, you've probably just caused the TC to unlock. If you immediately turn the overdrive off and the RPMs jump again, the first "shift" was not a kickdown to third, the second was. Note the RPMs at various speeds and gear/lockup conditions and you'll be able to stay ahead of the game.

A transmission cooler is an inexpensive way to protect your transmission. They run about $50-70 and are easy to install and/or inexpensive to have installed. Many opt for the 24,000 lb. GVW rated units for motorhomes and such. If you live in an area where it gets really cold, make sure you install the cooler in series with and BEFORE the factory cooling circuit integrated into the radiator to prevent over-cooling of the fluid. If the aftermarket cooler over-cools, the fluid will pick up some heat from the radiator before returning to the transmission. Obviously, during hot weather, it won't "heat" the fluid since it will still be doing its job as if the aftermarket unit weren't there.

Having the fluid flushed with synthetic will also help quite a bit. It's expensive, the 15-18 quarts of fluid alone will run you about $100 on top of the cost of the service, but it's worth it. I've got 30,000 miles on my Mobil 1 ATF and it looks absolutely good as new.

The rest of the driveline could benefit somewhat from new fluids. Here's my how-to: http://mywebpages.comcast.net/xterra...uid_change.txt
Brent

[bennett_taylor]

Thanks for the reply, I am glad you feel comfortable with it. I work in the factory robotics industry, and power transmission is a major part of what I do. I do understand the idea's behind turning off overdrive and such, and OF COURSE, I keep the overdrive off while towing. As far as changing fluids, I will do it! Thanks for the how-to's. I was going to get a cooler installed before this last trip, but got called out of town and never got it done, prolly will for next long trip. As far as the overdrive thing, being an engineer, working with torque, speed, and power on a daily basis, I really understand this stuff. I will share some of this with anyone who doesn't know and is interested. I find that this is one of the most misunderstood areas. Someone once told me to turn off overdrive to keep the truck from shifting in and out of 4th gear....while this is probably a good reason, it is not the key reason. Lemme shed some light on this.

First off, to pull a boat up some hill (or even cruise at a constant speed), it will take X amount of power...pretty simple...

Engine Power(HP) = Torque out of the engine X RPM Engine

Therefore, the higher the engine RPM's, the lower the torque the engine
needs to produce to achieve said power. Input torque into the tranny is what wears them out and heats them up. If you turn off overdrive, your RPM's will be higher, therefore reducing the input torque. This is the primary reason for turning off overdrive.

Thanks for the feedback.


Bennett Taylor

[Schludwiller]

Yeah, it's like my friend who drives me nuts every time I ride with him. He shifts through the gears so freaking quickly that he's chugging at 12-1500 rpm's. in way too high a gear. So different situation, same result. You can hear his tranny groaning every time he steps on the gas at 20 mpg in 4th gear.

Drivers nowdays can't seem to handle things more complicated than a button, so the manufacturers just say "turn off the button" when towing. There are instructions right above the drivers head on how to engage 4wd in the Xterra, but it's still a mystery to millions of drivers out there. That's why the big SUV's now have a "4x4 button".

[bennett_taylor]

Oh Yea, I know the type's. They think high RPM's are bad for the car. Little do they know, that they are asking WAY too much torque out of the engine, and putting that torque into the transmission.

[trigger2000]

Great read, but a bit confussed. I'm sure I'd read something in the owners manual, that you shouldn't be out of O/D for long if you are travelling at high speeds. I'll be taking a trip soon, with a trailer aprox. 2500 full weight and traveling at highway speeds, or at least 50-60 mph. Should I be leaving the O/D off for the full trip, or just when I'm dealing with hills, and merging into highway traffic?

[Schludwiller]

Your tachometer is the best gauge of what is "good" for your engine. Like the post above, don't let your engine lag, or let it run at high RPM's for long periods of time either. Most people with manual transmissions are pretty familiar with the best RPM's for their engine, but Auto people tend to rely on the automatic shifting instead (thus the OD warning for automatic types).

editorial comment: In "general" Automatics while convenient, have removed many peoples understanding of their engines. It's unfortunate with the proliferation of automatics that many can't even drive a manual if situations arise where their lives or others depend upon it.

[rrdstarr]

Originally posted by Schludwiller


editorial comment: In "general" Automatics while convenient, have removed many peoples understanding of their engines. It's unfortunate with the proliferation of automatics that many can't even drive a manual if situations arise where their lives or others depend upon it.

Ditto to that! I have never owned and auotmatic and hopefully won't have to for a long time!!!

[ChuckH]

Just have to add another comment on driving a manual transmission.

IMO, being able to drive a manual transmission should be a requirement for attaining a driver's license except in rare cases where a physical problem or such may make it impossible. It is my belief that people who know how to drive a manual transmission are generally better drivers because they tend to be more attentive.

I learned how to drive a manual transmission at a very young age. It was great having older Sister's and a Brother, uh, at least in that respect.

[OffroadX]

60-65 with overdrive off is probably about as fast as you'll want to go. I think that's about 4000 RPM.

Brent

[sis27]

How does turning O/D off affect the gas mileage
Simon

[OffroadX]

Someone on XOC did some testing and found he got better mileage when he turned it off when it was called for. If you leave it on and the converter is unlocked, you're turning higher RPMs than if it were locked, but those extra RPMs are doing little to keep you moving and most are just being wasted stirring the fluid and generating heat. If you turn the overdrive off so that the converter can stay locked up in third instead, you're running still higher RPMs but none are wasted.
Strictly speaking, higher RPMs = lower mileage, but if done properly, you can come out ahead.

Brent

[sis27]

So does it pays to just leave it off during city driving(i.e. w/OD off my truck uses 2.3k RPM down my street, with it on it drops down to 2K RPM) Then why does it automaticly kick on when I start the car?
Simon

[trigger2000]

Thanks for the help. I too was a manual driver from the start, and prefer manual, however life changes and I now have an auto, which has taken some getting used too, ie trying to clutch, and shift.

[OffroadX]

The system defaults to Overdrive On for a few reasons. One is the fact that it's there for fuel economy in the first place, having it default to off would piss off most of the ignorant owners that never give it a second thought and bitch about getting 14 MPG on the highway, not to mention piss off the EPA. The other reason is because it's not really a problem for it to be on under 95% of the conditions the vehicle will be found in. Towing (or heavy loads) and steep/mountainous roads are the only times it's really not a good idea for it to be on.
Me, I turn it off whenever my speed is frequently varying between 35 and 55 MPH since the converter doesn't lock up until 45 MPH or so regardless. This keeps me off the brakes somewhat (better engine braking), helps fluid temps a bit, but more importantly it helps preserve the lockup clutch since it would otherwise be constantly engaging and disengaging and like any clutch it will eventually wear out. I also turn it off when merging, passing, or any time I want a little extra pep without having to floor the pedal and force a kickdown to third gear.

Brent