Towing Cars on all Four Wheels

[George7941]

Since we are concerned about lack of proper lubrication in the tranny in this situation, what about keeping the engine running during a tow of an automatic tranny equipped vehicle? This would ensure oil pressure in the tranny since the pump is running.

Also, same question with a manual tranny car. Input, output and countershafts will be turning with the engine on and the car moving. Would this not ensure proper lube of the tranny internals?

 

[Colt45ws]

I suppose you could with an automatic. I dont see the point with a manual though. Just make sure the manual is in Neutral.

 

[bdcardinal]

had more than a few cars brought it that were towed while in gear. the engines overreved and floated, then broke valves.

 

[onion]

Originally Posted By: bdcardinal
had more than a few cars brought it that were towed while in gear. the engines overreved and floated, then broke valves.


Well, one would assume that he'll be towing in neutral. Let's hope so.

Yes, in theory that would work just fine- towing with the automatic transmission in neutral with the engine idling. The pump will be running... should be fine. Of couse, if you're towing a car that way long-distance and the engine dies for some reason and you tow it 2 hours with the engine shut off... you'll likely need a transmission.

Same goes for a manual, really. I gotta disagree with Omno here. You can tow a manual-transmission vehicle in neutral for short distances, but if you're towing for any significant distance or at highway speed with the engine shut off, it can tear up even a manual transmission. Most manual trannys rely on the countershaft to be spinning to sling & distribute oil through the transmission- and the countershaft will turn ANY time the clutch is engaged with the engine running (neutral or in gear). But when flat-towing with the engine off, only the output shaft will spin... and it's usually well above oil level.
And it won't get proper lubrication when the engine isn't running.

The RV crowd has several favorite vehicles- most of them small, light 4wd's (the geo tracker and assorted Jeeps come to mind- I'm sure there are others). They can flat-tow these vehicles because the transfer case can be disengaged... so that the output shaft of the manual transmission doesn't turn. Can't do that with just any ol' manual-transmission vehicle, though.

 

[mstrjon32]

Originally Posted By: onion
The RV crowd has several favorite vehicles- most of them small, light 4wd's (the geo tracker and assorted Jeeps come to mind- I'm sure there are others). They can flat-tow these vehicles because the transfer case can be disengaged... so that the output shaft of the manual transmission doesn't turn. Can't do that with just any ol' manual-transmission vehicle, though.


Gotta love N on the transfer case.

 

[Colt45ws]

I doubt idling 500-600RPM is going to be throwing any oil around off the countershaft.

 

[mechtech2]

I've seen many experienced tow truckers either disconnect the driveshaft , or keep the engine running when flat towing large manual trans trucks.
Some parts are very well lubed , but some may not be.

 

[George7941]

Originally Posted By: Onmo'Eegusee
I doubt idling 500-600RPM is going to be throwing any oil around off the countershaft.


The mechanism for oil distribution is not so much oil being slung off the countershaft gears as it is the oil climbing up the countershaft gears and then on to the meshing gears of the input and output shafts. 600 rpm idle speed should be enough for oil to be distributed this way.

 

[onion]

Originally Posted By: mechtech2
I've seen many experienced tow truckers either disconnect the driveshaft , or keep the engine running when flat towing large manual trans trucks.
Some parts are very well lubed , but some may not be.


Yeah, I've put lots of heavy truck driveshafts back in for exactly that reason: the tow truck driver will disconnect the driveshaft so that the transmission won't be damaged. This is done with both automatic and manual transmissions. And the same rule applies to automotive applications- except that they're usually light enough that the drive wheels can be raised when being brought in via wrecker. In some cases it's impractical or impossible with a semi.

About flat-towing with an automatic- I've read that there are aftermarket lube pumps that can be installed on most any automatic transmission to allow flat-towing with the engine off- mostly for RV geezers. Never seen one... don't know how they work... I've just heard that they exist. And that they're expensive.

 

[George7941]

Would the tow truck driver disconnect the driveshaft if the engine is operational or would they only do it if the engine was having problems and could not be idled while towing?

An experienced person could probably disconnect the driveshaft and support it in under ten minutes with a Tiger Tool U-joint puller and an impact wrench. But that is ten minutes by the side of the highway with semis whizzing by at 60mph. Not a safe place at all. If there is a blizzard happening or even at night it is going to take longer than ten minutes. So wouldn't the sensible thing be to idle the engine when possible and flat-tow the truck?

I will grant you that the majority of times a truck needs a tow is when it is experiencing an engine problem.

 

[Dualie]

Originally Posted By: George7941
Would the tow truck driver disconnect the driveshaft if the engine is operational or would they only do it if the engine was having problems and could not be idled while towing?

An experienced person could probably disconnect the driveshaft and support it in under ten minutes with a Tiger Tool U-joint puller and an impact wrench. But that is ten minutes by the side of the highway with semis whizzing by at 60mph. Not a safe place at all. If there is a blizzard happening or even at night it is going to take longer than ten minutes. So wouldn't the sensible thing be to idle the engine when possible and flat-tow the truck?

I will grant you that the majority of times a truck needs a tow is when it is experiencing an engine problem.


No its remove the shaft EVERY TIME. You can also pull an axle shaft.

But any good tow operator will insure that the link between the drive wheels and the vehicles transmission is not connected. their are many less than TOP SHELF towing outfits that will idle the engine but this is NOT an accepted industry practice.

 

[onion]

Originally Posted By: George7941
Would the tow truck driver disconnect the driveshaft if the engine is operational or would they only do it if the engine was having problems and could not be idled while towing?

An experienced person could probably disconnect the driveshaft and support it in under ten minutes with a Tiger Tool U-joint puller and an impact wrench. But that is ten minutes by the side of the highway with semis whizzing by at 60mph. Not a safe place at all. If there is a blizzard happening or even at night it is going to take longer than ten minutes. So wouldn't the sensible thing be to idle the engine when possible and flat-tow the truck?

I will grant you that the majority of times a truck needs a tow is when it is experiencing an engine problem.


I agree with dualie- except that I'll word it more pleasantly:

I've personally never seen a truck towed in with the engine idling. That's not to say that it wouldn't work... but it's generally not done. And, yes, they often just pull an axle shaft (better yet, two... as towing with only one axle pulled won't do the power divider any favors).

But I mainly work on trucks and heavy equipment... not sure what the standard practices are in the automotive industry. But I think it's safe to assume that they're similar. If vehicles are towed with the drive wheels off the ground, then this is all a non-issue. Same as the trucking industry.

 

[ViragoBry]

Aren't there some cars that don't pump transmission fluid until they're put into D or R? I know from experience that the Chevy Celebrity's transaxle doesn't pump fluid in P or N with the engine running.

 

[moklock]

If it were a car being towed regularly on all fours such as behind an RV, it would be best to use a car where the trans is already approved by the mfr. for flat towing.

The Saturn S-Series have also been popular w/ the RV croud for such reason. Their transmissions, either manual or auto., always have enough parts in fluid at all times that the splashing fluid is always enough to keep everything well lubed.

Most cars w/ GM 4T40-E auto transaxles are also flat towable for unlimited mileage due to the trans. having a small built-in aux. fluid pump connected to the output side to keep the parts lubed while being towed.

Some other auto trannies also allow flat towing w/o adding a lube pump (Honda IIRC) but also require a pit stop after every so many hours of towing to idle the engine and go through the gears to re-lube everything.

 

[TylerL]

Motorhome Magazine puts out a list of cars and trucks that can be flat towed for at least 200 miles and a minimum speed of 55 mph.
Dinghy towing guide
They have guide for each model year from 2002-2009.
Moklock: according to this the only Honda car that can be towed for more than 200 mile going at least 55 is the 2009 Fit Auto/manual. It also list the CR-V as dinghy towable.

Some of the Cars that made the list:
Toyota cars with manual trans,
All Subarus with MT,
Nissan cars with MT,
Ford Focus MT and Fusion MT,
Several GM cars with AT or MT, (Most Saturns)
one or two Crysler cars with MT's
HYUNDAI cars with MT's

Trucks/SUVs
Some are dinghy towable especially ones with 4x4 because they have transfer cases that can be put in neutral.

 

[moklock]

The CR-V and the Honda 3.5-powered Saturn VUE were the ones I was thinking of, the guide describes it as:

1) Recirculate transmission fluid every eight towing hours following the procedure in the vehicle owner’s manual.

It looks like the GM 6T70-E six speed auto can also be flat towed but a similar procedure has to be folowed.