Transmission damage

[JUSTFISHING]

I would like answers from people that have mechanical experience not just an opinion .

 

1. What actually happens to a standard truck transmission that is damaged from towing with out pulling the drive line , and how far would it take to do such damage ?

2. Next if towing a 3 axle tractor  from the front and chaining the forward axle up before lifting so when lifting the forward axle is off the ground  will it not turn the drive line in effect likely  to not damage transmission  ?

3. If you have a truck that the engine still runs and you left it running during the tow is the oil in the transmission churning around inside enough to not cause damage while towing ?

Again these questions are fielded to persons with knowledge in transmission operation and rebuilding 

 

 

thanks in advance 

I know just enough to be dangerous

[goodmichael]

It depends on the manufacturer of the gearbox. If a transmission is towed with the driveline in place, you are still turning the rear output shaft. The guts of the transmission are possibly being engaged in reverse order. There is always the possibility that the gearbox is low on fluid or while in tow, is slanted to where the lubricating fluid is not slung to where it needs to be. Towing a vehicle with the engine running also does not consider the angle that the vehicle is riding at while moving. The engineers that design a gearbox design it to run with all wheels on the ground, not while in tow.

If you are towing a vehicle, it is always a best practice to tow the vehicle within the guidelines of the manufacturer's specifications. This is for the particular gearbox.

It is a difficult task to prove that a vehicle was damaged due to preexisting wear, or by failure to properly follow recommended procedures.

[brian991219]

As goodmichael said above, the answer varies based upon the exact make and model of transmission.

 

For the most part modern manual transmissions are lubricated when the input shaft is being driven by the engine, it will pickup and sling lubrication. When the transmission is being driven from the output shaft little, usually no, lubricant is flowing. For short distances there may be enough residual lubrication on the components to prevent, or mask damage. Longer distances will result in heat buildup. This may not lead to an immediate failure but will reduce the life expectancy of the transmission significantly. This is perhaps the biggest reason to not chance even a short cross town hop -you do not know how many times that trans has been abused prior to your tow.

 

Leaving the truck running with a manual transmission will provide some lubrication but not the same as when being driven. First, the truck is elevated so the oil will naturally go to the lower end of the case and not stay in contact with the sling pump. Second, the trans is in neutral so the oil is not being carried across the gears and shafts, it is just being splashed around. The meshing action of the gears transmits oil across all the affected parts.

 

As for lifting the front drive off the ground, for the most part it will stay stationary, although it can turn when you hit a bump or dip in the road. This is why when towing iShift or mDrive automated transmissions it is important to pull the driveshaft or all 4 axles, not just the ones on the ground. With those transmissions even the slightest movement after the engine has shut off will cause catastrophic failure.

 

Another consideration when front towing, some newer differentials are angle sensitive. Freightliner has a technical bulletin out about lifting over a certain angle (I don't recall exact figure), as it will not allow the gears to be lubricated properly. These require removal of all axle shafts.

 

Bottom line, failure to disengage as much of the driveline as possible before towing will lead to heat buildup and early failure of components. It may not happen while the vehicle is in your custody, but it will contribute to a later failure. Would you want someone doing something to your property that would shorten it's life? I surely would not.

 

Speaking from personal experience, I was lazy twice in my career and both times it bit me hard. One was a disabled dump truck, older Autocar with a RoadRanger 18 speed. Died in motion, only towing it 5 miles. Did not pull shaft, transmission locked up and the shaft twisted off like a pretzel. Took out the fuel tanks, air lines, hydraulic tank, PTO (dump truck) and more. Ended up paying almost $10,000 to fix the truck, lost a good customer and hurt my reputation. The other was an $8,000 rebuild on a transmission in an ambulance, again 8 mile tow, bad weather. Didn't pull the shaft and ended up rebuilding the transmission.

 

Here is a video on how the Eaton precision lube system works. This is the most modern manual transmission lube system, not all transmissions are lubed this way. Even still, you can see that tilting it up will take lube away from the pump pickup and reduce the effectiveness. https://youtu.be/jP6-EZjN9DU

 

Here is a generic transmission lubrication video by Shell Oil. This is how most transmissions are lubricated, even still today. https://youtu.be/B8zEpFbM7LY

 

 

[goodmichael]

Also when you are stopped in traffic such as a red light, and you take the vehicle out of gear and let off the clutch, your input shaft on the transmission is still spinning, and engaging (moving) the internal parts of the transmission. While engaging the clutch does wear on the throw out bearing, it does not wear the internal guts of the transmission.

Transmissions are one of the most neglected components of a vehicle, be they an automatic transmission or manual transmission. People generally do not give them any concern until there is a problem, by then it is too late, there is damage that can not be reversed.

[Njsss]

Keeping clutch depressed when stopped causes unnecessary wear of throw out bearing, pressure plate &  **engine thrust bearing **

[goodmichael]

That is true, it does engage the throw out bearing, but which is the least expensive repair, a throw out bearing and pilot bearing or internal gears inside the transmission? If the vehicle is out of gear, the input shaft is being engaged (turned), and the internal parts (gearsets) of the transmission are moving. It probably will not matter in the near future, as manual gearboxes are going the way of the carburetor. Many , not all, but many, drivers who are not operating their own equipment tear up a clutch due to misuse faster than the throw out and pilot bearings go bad on their own. I see many who feather the clutch as they back up to a casualty, rather than using the brakes. If you own a vehicle, your treatment of the vehicle is usually at a totally different level, as the repairs come out of your ass pocket.

[Njsss]

keeping clutch depressed forces engine crankshaft forward causing wear on internal engine bearings,  clutch linkage, cross shaft, etc.  running in neutral causes minimal internal transmission wear(as long as trans oil is serviced & at proper level). 

 

[goodmichael]

If the transmission is in neutral, the internal parts of the transmission are engaged and are turning due to the input shaft spinning. If the clutch is engaged, the throw out bearing is engaged. I look at it from the point of view of which is less expensive to change, a throw out bearing or having to press on and off internal bearings and gears. While the flywheel is bolted to the crank directly, I have been instructed in trainings, that the force is distributed onto the flywheel and does not effect the main bearings at all. This minimal pressure is absorbed by the miniscule thousandths of an inch crank end play as well the gap between bearings and the crank that are sealed with oil as the engine is running. I am attending a Ford factory training before the end of the year on the 6.7, and I will discuss this with the trainer.

[Njsss]

In neutral, the input shaft turns countershaft which turns main shaft gears under no load-freewheeling-essentially no wear 

Thrust bearing controls for/aft movevemt of crankshaft. Constant force forward (depressing clutch) will cause wear- especially in heavy traffic areas

Along with throw out bearing, all clutch linkage will wear

[Njsss]

All manual transmission damage is a reault of lack of maintenance, incorrect oil level, driver error(misshift, PTO left on, things they neglect to tell you, etc)

just my opinion,  what ive seen over last 35 yrs