Towing in overdrive

[purplepickup]

I do a lot of towing with all my vehicles and they are all automatics with overdrive.   I have a number of trailers and match the weight I tow to the capabilities of each of my vehicles.  I tend to keep the trans in OD if there isn't a strain but in hilly areas I try to anticipate when the shift to direct will happen and do it manually.    Once in a while I get caught off guard and the trans will shift before I do it manually.   Am I hurting the trans?

I know the common recommendation is to not tow in overdrive but I've towed in OD for many years without any tranny problems.  I change fluid and flush about every 40-50K miles.  I'm just wondering what you experts might say.  Gas mileage is considerably lower if I don't use OD.

[enjenjo]

I'm not an expert, but the service manager at a local ford store lives down the street, and told me using OD is fine on my Escape, as long as you don't exceed the tow weight recommendations, and have less than 600 lbs in the car. He also told me if you are in hill country, and it's down shifting a lot, turn the OD off. The owners manual on the HHR I just bought says basically the same thing. With my Ford trucks with the 4R100, I tow in OD all the time, except in the hills

[Rrumbler]

When I got my first truck with an OD trans in it, I asked the service manager at the dealership about that; he said: "it's an automatic transmission, let it do it's job."  Since that time, I have only locked out the OD after it kicked down, for a long pull, so it won't hunt back and forth; no apparent harm in a lot of miles in western mountain towing.[/i]

[Digger]

I pull a 24 ft enclosed trailer usually with a car in it all the time in OD. The "Burb" has around 250K on it with no problems.

[phat rat]

As long as the trans isn't always hunting for what gear it wants to be in I wouldn't worry about it. Back when I had my 94 Burb w/350 I usually got better mileage towing in drive instead of OD. But that was with one size bigger tires. When I went back to stock size it was different. It just depends on the gearing

[wayne petty]

sorry to break in guys... somebody posted this fix over at another forum i hang out at..



where the TCC won't stay locked at cruising speeds.. because of P0300 random misfires..

   
Murray Freeman Murray Freeman
New User | Posts: 1 | Joined: 12/13
Posted: Today 02:12 AM

I'm posting this everywhere I can find.

Some of you know that I've been chasing a random misfire (P0300) for several months now. I'm pleased to say I THINK it's been resolved. And in the most obscure place.
Skip to the bottom if you only want the "punch line".
Items checked and/or replaced.
I have a code scanner to help identify pending codes and current codes.

Spark plugs
Plug wires
All four O2 sensors
Took it to shop #1 for them to diagnose. They checked....
Fuel pressure
Fuel flow
Vacuum quality & quantity
Coils for quality of fire
Moved even side coils to odd side to see if coils were issue. Were not.
"Relearned" crank sensor
Checked entire system for vacuum leaks under all RPMs.
Then they ended up saying "Maybe weak valve springs".
Shop #2
Checked all the same items above and only found worst misfire count on Cyl #6.
Replace #6 plug and result was the same. P0300.
Swapped MAF sensor to "test" with no change. Then swapped it back.
Gave it back to me so they could "do more research".
Never hear back from them.
I took it to Smedley's Chevrolet and walked the service writer through everything that's been checked and done.
"I see it periodically. The valve train is just worn out."
I could actually see this being the case as it had, at the time, 403K miles on it.
I ordered valve springs, as a last result, from gmpartsnow.com and replaced them on the 4,6 & 8 cylinders since those were easily accessible by the spring compressor I had.
No change. P0300.
Still had a "random misfire" at 69-75 MPH.

Through ALL of this time I had been reading various blogs about other Chevy owners and their P0300 woes.
I was NOT alone.
But until Wednesday almost everything that I had read had already been checked or replaced on mine.
But on Wednesday I read one blog about a guy with a 6.0L that was stumped and staring at his engine while his kid revved it up to the 2000-2400 RPM range, where he had his misfire. He noticed what I later learned was called "belt slap". It's when your serpentine belt "slaps" back and forth during certain RPMs.
This causes a vibration that shutters through the engine and supposedly CAN disrupt the balance of the crank shaft. The crank sensor picks of the disruption, identifies it as a misfire on the cylinder the crank position is in at that split second, and moves on. Enough of those falsely identified misfires and the computer stops allowing the transmission to shift into lock up. Then kicks out the pending P0300 code. Bummer. That's running 200-300 RPMs more to do the same speeds on the highway. Fuel economy drops.

Well, my tensioner pulley blew up a few months ago right before a pick I had in ATL. I replaced it and the belt in the lot at Advance Auto Parts & made my pick. I was already staring at my CEL for a bad O2 sensor but that code started being paired with the P0300.

So this Wednesday night I replaced my serpentine belt and now, 150 miles later, NO CODES!!!!!!

Check your belts for "belt slap". Occasionally belts are defective & unbalanced. A balanced belt does not slap without the a/c on unless there is some other issue.

UPDATE - About 4000 miles later (about 1.5 weeks for me) and still NO CODE!!!  Woohoo!!!  

Read more: http://forums.automotive.com/70/8583078/transmission/4l80e-tcc-doesnt-stay-engaged/page2.html#ixzz2oMJZTxla


all i can say to this is AHHHHHAAAAA!!!!!!!

wayne..

[purplepickup]

Thanks guys.  It sounds like I'm doing ok even if I don't catch every downshift before the tranny does it.  I try to use common sense and not let the tranny search much.  If it does I just keep it in drive.  

It's just one of those things I've thought about while driving long distances and have meant to ask for a while.

[parklane]

My 06 Dodge with a Cummins has a button on the end of the gear selector, that you push once, and puts the trans in the Tow/haul option. This changes the shift points, and also allows the trans to help slow me down in 3rd gear. I use this position even if not towing.