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Towing and transmission damage

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Michael Oritt

Michael Oritt

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I have heard that when towing a car with a manual transmission the driveshaft should be disconnected to prevent the transmission mainshaft from spinning because it is splash-lubed when the car is running in gear and it would thus be turning without lubrication.

Others have told me that there is absolutely no problem and/or that the mainshaft bearings are probably impregnated with lube and towing for distances of under 500 miles or so would be okay.

I'm not concerned with what towing does to the Overdrive as I have a Toyota transmission on my car. What is the collective wisdom?
 
HI Michael,I think to be on the safe side I would disconnect the drive shaft. I think where failures have been encountered in the past is where the car is towed with the front end elevated.However,any time I move a car any distance when it is not being driven its on a flat bed.---Fwiw---Keoke
 
Hi Michael, I would think with a Toyota transmission it would be okay to tow without disconnecting the driveshaft. However, for those of us with an original transmission I would never tow without disconnecting the driveshaft. The reason is, as you indicated, the layshaft will continue to turn, and assuming your towing in neutral, without lubrication. The large roller bearings in the front and rear of the transmission need to be constantly lubricated. Perhaps under 50 miles would be okay, but not any long towing.
 
Hi Johnny,
When towing with the transmission in neutral, only the output shaft & the synchronizer hubs are turning. The input shaft, the counter shaft, & associated gears & bearings, only turn when the clutch is engaged with the engine running. The large "roller" bearing in the front is not turning. The rear bearing however is turning.

Provided that the transmission has overdrive, the OD pump, which operates from the output shaft, will be constantly pumping. Once the accumulator is filled, the remainder of the pump flow exits via the bypass valve & recirculates back to the sump. I think this creates enough lube circulation to handle the lube to the rear bearing & to the input shaft to tail shaft bearing.

At least I have towed considerable distances, 900 miles plus, with the drive shaft connected & no harm to the transmission.

Toyota (no OD) recommends starting the engine with gearbox in neutral for a few minutes every 200 miles to relube the transmission when towing.

Opinions may vary.
D
 
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