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MG TD TF 1500 - Can I use a Tow Dolly
|I have a 52 TD with the Moss Sierra 9 five speed gearbox. Does anyone know if towing this car with one of the front end two wheel tow dollies will harm the transmission?|
|I would say you need to pull the driveshaft. |
Wait for it....
|I agree, David.... and I've rebuilt a lot of gearboxes. But yeah, there's loads of folks who will say we're being overly cautious (at the very least). Knowing how a gearbox works, and how the oil flows, I would never flat-tow a manual transmission car for more than a few miles without disconnecting the tranny.|
Remco Drive Line Coupling is the way to go.
Google them and read all about it.
The system has a sliding spline at the differential end of your tail shaft and is operated from a pull cable from within the car.
The car can then be flat towed without the unnecessary use of a car dolly.
My brother in law has ordered one for his car to be towed behind his motorhome here in Australia.
They are in USA.
|Rob, I looked up the Remco and while it is great for someone who does a lot of towing it will probably be better if I follow the advice given and just disconnect the drive shaft for the once every year or so I might need to tow the car. Thanks to all who responded. In truth it might be wiser to just rent a trailer for the occasional use I have in mind.|
|One thing to keep in mind - the differential. If the u-bolts over the axles are not fully tightened it is possible for nose (input side) of the differential to rotate downward. The driveshaft prevents this from happening in normal circumstances. Bud|
|OK... I'll ask why?|
Why would a piece of machinery (gearbox) designed and proven to propel a car 100,000 miles under various loads and driving conditions suffer damage while turning under zero load?
Isn't saying 'towing your car is bad for your transmission' like saying that coasting in neutral is bad for your transmission? I don't see where the damage comes from.
|I think I've probably written this before somewhere, but I'll repeat it here again, for posterity. (Note: I fully expect an onslaught of folks saying I'm wrong... so be it. I've worked on way too many transmissions and I do know from whence I speak.)|
There's a small bearing in between your input shaft (the one that runs at motor speed with the clutch engaged) and the output shaft (the one that runs at 'road-speed' via the drive shaft). That little needle roller bearing is lubricated by oil forced through small holes in the input shaft gear when the input shaft gear is meshing when the engine is running and clutch is engaged. If the input gear is not turning, which it is not when the engine is stopped, then no lubrication is forced into this bearing. Also, under normal running circumstances this bearing does not turn very fast - the input and output shaft rotational speed differences are controlled by the shifted gears and in top gear the bearing does not turn at all - the two shafts move the same speed (1:1 ratio). But when towing, this bearing spins like mad because the input shaft is stationary and the output shaft is spinning at road-speed. So... the bearing is spinning like mad and the input shaft is not turning so no forced lubrication is happening... this is *not* a good situation, and will shortly lead to galling of the surfaces on the input and output shafts in this bearing location. Over time, this allows the center shaft assembly to flex (because the bearing is now very loose and sloppy due to deterioration) and this can result it excessive wear to the gears, tooth breakage and popping out of gear.
Coasting with the car in neutral is not quite as harmful, since the clutch is engaged and some lubrication is happening, though the needle bearing is still spinning like mad. I tend to avoid coasting in neutral for just this reason and many operator manuals back in the day did caution against this behaviour.
|kmclemore, please don't think that I'm doubting you, I'm just curious. Are you saying that the needle bearings (the spigot bearing rollers, #58 in WSM) are lubricated via oil coming from the first motion shaft (#52)? I'd never heard of that before. (But there are many things that I'd never heard of before.)|
In this particular case, that might not be significant. The gearbox in question is not an XPAG. It's a Sierra 9. Might it not have a different lubrication system? Bud
|For starters, if one intends to use a dolly for a T car, they'd better measure it in advance because it is too narrow for most dollies. I had to weld a channel to the inside of one of the ramps to accomodate ours.|
|kmclemore, that makes sense. Thanks.|
|"Are you saying that the needle bearings (the spigot bearing rollers, #58 in WSM) are lubricated via oil coming from the first motion shaft (#52)?" |
Yep. When the engine is running, oil gets squeezed between the gear on the first motion shaft (aka "input shaft") and the cluster gear, as they are in constant mesh, and little holes in between the gear teeth on the first motion shaft gear allow that squished oil to flow up into the spigot bearing (aka "roller bearing") and keep it lubricated. No rotation of the first motion shaft = no lubrication (apart from whatever small amount might find its way in there).
"In this particular case, that might not be significant. The gearbox in question is not an XPAG. It's a Sierra 9. Might it not have a different lubrication system?"
Most gearboxes work the same way, though I've never done a Sierra 9 - I suppose you could ask a Sierra expert, but I'd put good money that it works the exact same way. I've worked on gearboxes from MGs, Triumph TRs, Spitfires, Austins, Sunbeams, Morris Minors, Jaguars, Reliant Sabres... well.. lots of LBCs... and they all work that way.
|Another factor to consider is the oil level itself. 20 years ago or so Toyota pickups had transmission failures that were eventually traced to driving up long grades ( like Eisenhower tunnel around here) The front bearing wasn't getting any oil. May have the same effect depending on how high you get the front wheels off the ground. I know nothing about the Ford box but some of the new gearboxes have oil pumps to get the oil where it needs to be...could possibly be an issue there...I have no idea.|
All things considered its a lot easier to drop the drive shaft than pull a gear box and rebuild it...particularly if it's just getting towed to a destination and no driving intended along the route.
|kmclemore, that is by far the best explanation I have seen of why towing with the drive shaft in place is harmful. Thanks for posting. Paul.|
|"All things considered its a lot easier to drop the drive shaft than pull a gear box and rebuild it..."|
It's only 4 small bolts, and you can even leave the shaft in the trans - just retract it enough to clear the diff and then hang it inside the tunnel. When I was a poor-boy racer I used to flat-tow my car to races, and I installed a small loop hanger above the back of the tunnel for just this purpose... I used a bungee around the shaft and linked its hooks to the holes in the shaft's rear flange to keep it stuffed in the tranny.
If you do remove the shaft you risk losing all the gearbox oil, so either do the above or get a spare drive shaft splined nose piece and securely stuff in the gearbox.
|Thanks, Paul. |
Here's a first motion shaft from an BMC-made Austin Healey Sprite, for example... note the small hole in the gear mesh area... this lubricates the spigot bearing, and the first motion shaft doesn't turn if the engine is off.
|OK, so I checked - the Ford Sierra is a bit different - as with some other gearboxes, it picks up the oil for that spigot bearing off the oil being slung out of the main first motion shaft's large ball-bearing instead of being squished into it by the gear itself. (Note the small hole in the front of the first motion shaft's gear... that sits adjacent to the rollers on the first motion shaft ball-bearing and will pick up oil being squished out of that bearing when rotating.)|
However, the same problem exists... engine off = no rotation of the first motion shaft = no rotation of the first motion shaft's ball-bearing = no oil to the spigot bearing = damage to the spigot rollers as well as the first motion shaft and the main shaft bearing surfaces.
|Thanks for the detailed info, kmclemore. Some more things that I didn't know before, but do now. Bud|
|I have towed my TD on a two wheel dolly.|
I back the car on, straighten the front wheel and tie the steering wheel off with a rope. The rope does not need to be supper tight the steering wheel can move two or three inches back and forth, just enough so the wheels stay straight. I loop the rope around the brake peddle and then loop it acouple times around the bottom of the steering wheel and tie it off.
Is there a reason the car should not be towed this way?
|I towed my TD 550 miles at speeds less than 55MPH on a U Haul tow dolly with no problems and I've been using the car for 4 years since. The car fit this U Haul unit with no problems.|
|John Quilter (TD8986)|
|"Is there a reason the car should not be towed this way?"|
The main reason would be if you have wire wheels you run the risk of the knock offs coming off the car and losing a wheel.
Steel wheels so no knock offs.
This thread was discussed between 07/03/2015 and 09/03/2015
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