Motorhome Tow Vehicle

gmc
sonoma

#1

I towed a 95 Chevy S10 (5 speed manual trans.) behind my motorhome on all four wheels for over 40,000 miles with no problems. I recently bought a 2003 GMC Sonoma (5 speed manual trans.) Basically the same vehicle. The Sonoma owners manual says I cannot tow it on all four wheels for more than ablout 35 miles and then at a low speed…I now know that you can purchase a differential disconnect that will allow you to do this. (expensive)

Can you think of any other way I can tow this vehicle on all four wheels???

Thanks A Lot

Paul


#2

The reason you can’t flat-tow some vehicles is mainly because the transmission can’t lubricate unless the engine is on. There are add-on transmission oil pumps that you can get specifically for RV toads which will fix the problem. Camping World should know about it, as will the guys over at rvforum.net


#3

I would really like to know why the S10 can be flat towed without damage (you proved this) but not the GMC, both are manual trans , so I can’t see how the “no lubrication” issue fits in" Give a call to the people who wrote the book.It is so easy to say “follow the owners manual” but these people get it wrong at times. Are you sure you are looking at the warnings for flat towing a manual trans vehicle?


#4

I’m not super up on GM trucks. Are we talking about the same manual transmission? No changes at all in the truck that’s 8 years newer?


#5

I walked the halls of a GM Dealer over 8 years and never saw or heard of a manual trans being built that needed the engine on for lubrication, automatic transmission certainly,do not flat tow an automatic unless steps have been taken, a few hundred yards at low speed is OK.

Shadow, manual trans technology is evloving but much is the same as 40 years ago.

BUT: we do need to know why it is prohibited.


#6

Does the manual specifically prohibit this with a manual transmission? I know of no reason this would cause a problem with a manual. Automatic, definitely, but not a manual.


#7

Towed in neutral the output shaft would rotate in its bearings, and rotate inside all the synchronizers and their respective gears as well. Without the countershaft being spun ( it’s in neutral, remember? ) there’s nothing moving lubricant out of the bottom of the case. The countershaft won’t even coast and provide a little lubrication because it’s connected via the pilot shaft to the clutch, hence it stays still unless the engine is moving.

Sure, it’ll survive better a short tow, and in many cases might even survive lots of long tows. Sometimes it’ll even survive 40,000 miles of towing. But it’s spinning the transmission internals with no lubrication, and that’s never a good idea, especially at highway speeds.


#8

I agree with JayWB with an additional thought. On the S10 with the T5 or Borg Warner the reverse gear on the main/output shaft will be turning in the oil when the drive shaft is turning. That will fling oil around in the main case lubricating the rear tapered roller bearing, pilot and thrust bearing at the output shaft nose, and all of the bearings of the stationary constant mesh gears as the main/output shaft turns inside. The overdrive constant mesh gear in the rear will be turned by the output shaft as it spins free on the countershaft, flinging oil around the tail shaft also lubricating the rear bearing and the drive shaft bushing in the tail extension.

The 2003 GMC uses one of the MG5, MY2, M50, or MW2 manual transmissions. All of the constant mesh gears in these transmissions are engage by clutch dogs to the main/output shaft. With the engine stopped all of these gears are stationary. As a result no oil is splashed around to the rear bearing, pilot bearing, or constant mesh bearings that have the main/output shaft turning inside. At high speed the oil film will break down and the rear bearing and/or the pilot bearing will probably overheat and fail. Also the tail shaft bushing for the drive shaft will not be getting lube.

Hope this helps.


#9

Thank all of you for your input. Now I know why the difference between S10 and Sonoma. GM person I talked to could not find the answer and neither could a couple of transmission guys. I am having a REMCO Differential Coupler ( system that disengages the drive shaft while towing)installed next Tuesday… It seems as though they don’t always work that great, but they do work
Paul Pesce


#10

Did the firm that is installing your disengagement device say they have seen damage on the new model manual trans truck from being flat towed?


#11

I had not started to tow it yet. I transferred all the stuff - Tow Bar/electrical,Re-painted shell,Bed Liner etc. Then, I was looking in the manual to see which fuse I should pull while towing when I found the towing info…I didn’t think to look for it earlier since I had no problem towing the S10