Gearbox damage from towing in 5th?

ashpool25

ashpool25

Forum Member
Joined
Jan 28, 2010
Messages
45
Location
Melbourne, Victoria, AUSTRALIA
One of the reasons I bought my 3G OB was the increased towing capacity compared to my 1G Liberty (1400kg vs 1000kg).

My proposed towing will include a small car on a light-ish trailer (~1250kg all up) and possibly a (yet to be purchased) camper trailer (perhaps 800 - 900kg?).

Over the years I have heard a number of stories of people damaging their manual gearbox by towing in 5th. Not specifically Subarus; one that springs to mind was a Pajero.

Anyway I was reminded of this when I saw a damaged 3G OB gearbox offered for sale (cheap) which had suposedly been damaged due to "towing in 5th".

In my 1G Lib I did a fair bit for towing in the 100,000km I owned it (from 200,000km to 300,000km) - all within the rated limit, and some of that involved some fairly significant highway runs with a decent load (say 700 -800kg). I often used 5th but only when on the flat. At the slightest hint of a rising grade, and certainly on soft surfaces, I was back to 4th or lower - and I am not aware of any issues with the box during this time (or subsequently) and it wasn't a new box to start with.

So can anyone shed any light on the "don't tow in 5th" mantra that I've heard from a few quarters?

Is towing in 5th inherently bad or is it more a matter of being sensitive to the road conditions and load?

And what is the nature and extent of the "damage" anyway?

Thanks in anticipation....
 
If you are driving at the right combination of revs and speed, relative to the load then I'd think it should be fine. (~2,500+/- rpm) then I'd think you should be fine.
I recon 'lugging' boxer engines is a bigger problem.
 
Sheeeet! I have towing a trailer (??? kgs) with a golf cart (425 kgs) on and off for a few months and happily cruised the Hwy at 110 km/h in 5th.
When starting off from a standing start I use the Low Range (Man.) for 1st and 2nd to get moving and then switch to normal High Range,
once I get momentum going, it feels easier to me on the car as a whole, the hardest part of the whole trip is at a set of lights on the way out to the golf course which are on a hill and I have to make a RH turn at the top of it.
​

parlkands902201150305pm.jpg
 
i tow about 900-1100 with my 99GT foz, 5 has been fine, as long as im crusing, but is not much good under acceleration, i think the weight has been up around 1200 kgs at times, still been okay upto 90kms, but at 100+ i have been vulnerable to speed wobbles, normally about 110km on bends/corners. i think im only ment to tow about 750, coz this trailer has not brakes?
shhh
 
d_generate said:
5th is a reasonably strong gear, I've never had a problem towing with it.
Click to expand...

Me either - and I've got an L series 5 speed gearbox powered by an EJ22 that's moved some pretty significant loads IMO.

I've also not heard about this 5th gear towing problem.

One thing that springs to mind is the centre diff - I've recently heard that as little as 7mm difference in tyre diametre between the shortest and tallest tyre on the EJ'd subi's can cause centre diff detonation or premature death basically. If you're towing a load and haven't got your tyre pressures correct this could be a big issue for the centre diff that will be constantly working to keep front and rear ends happy. If you've got odd wear on each tyre the problem will be worse.

I've heard this from a mate who's right into his subi's and their gearboxes - he builds them for a purpose from the engine right through to the tyre sizes including the gearbox and diff ratios... Crazy ******* but I love talking to him about what he's up to - I've had many ideas for my ******* box that I'm hoping to have assembled soon!

Cheers

Bennie
 
Also, IF it really is a 5th gear problem, the gearset can be removed with the gearbox still in the car - hard yes, but do-able - makes things less time consuming thus cheaper.

If 5th is the culprit, the dead unit can be swapped out for a new/second hand GWO unit.

Cheers

Bennie
 
Actually now I think about it I remember when I had my 5 speed 60 series Landcruiser I was warned about towing in 5th with that ................ but it never stopped me.
 
ashpool25 said:
Why would lugging a boxer motor be worse than lugging any other configuration?
Click to expand...
I have always found 4 cyl boxers to like higher revs, compared to 'Lake Michigan cast iron boat anchors'. :poke:
I have always thought it might have something to do with a greater propensity for gravity to interfer with the operation of a horizontal piston in the cylinder at low revs, compared to a (near) vertical piston and cylinder. Similarly, I think part of them being easy reving is that the pistons don't need to be lifted, as do those in the vertical block engines.
On a flat / undulating highway at speed I always feel like a flat 4 could benefit from an overdrive gear. Up hill / at lower revs / with a load it is equally obvious that they aren't low torque thumpers.
Having said that, I like 'em as they are. (Of course I might just be a silly old hippie who is just imagining that my Beetle and Subi engines have anything in common other than layout! :lol:)
 
my speedo stopped working and the suggestion from the Subie mechanic was that the gearbox had got a bit too hot probably while towing and allowed the nylon gear to strip. It may have happened moving house from Vic to NT, though I thought I took it easy on the road. As it was a gearbox out and split it to fix the bill was way over $1000 to replace the $20 nylon gear. I don't think that using 4th would have made any difference. Do you know what damage had been caused to the gearbox you saw advertised? might help work out if it was caused by 5th or some other overwork.
 
So the damaged nylon drive gear of the speedo died and took the rest of the box with it? I'd be surprised if it was the heat. I've been involved with numerous Subarus in motorsport- including the Bathurst 24 hour race, and they had no problems.
 
In my travels with my camper trailer I have had numerous conversations with fellow "towers" and most will tell you that you must never use 5th (or depending on the gearbox 4th or 6th) gears for towing. Most look aghast when I tell them that I use 5th in most situations that I would without the trailer. One guy with a 4 speed auto diesel Prado said his kept blowing oil out of the gearbox until he complained to his dealer who then warned him never to do it.
 
At home, the only problem I have with towing my Cub camper behind the L-Series in 5th, is my engine is too tired too pull up any sort of hill that continues for too long. Along the flat 5th is good, but with 475000kms on the engine, I am often down to 4th , or even 3rd for some hills. Again this is engine, not gearbox issues.

At work, I drive a 2005 Mitsubishi Triton 3ltr V6 5spd manual, towing a tandem trailer that weighs 750kg empty, and up to 1000kg when loaded. Once out of town and up to speed (90-110 kmh) it pulls quite fine in 5th.

Beigewagon.
 
Beigewagon said:
At home, the only problem I have with towing my Cub camper behind the L-Series in 5th, is my engine is too tired too pull up any sort of hill that continues for too long. Along the flat 5th is good, but with 475000kms on the engine, I am often down to 4th , or even 3rd for some hills. Again this is engine, not gearbox issues.

At work, I drive a 2005 Mitsubishi Triton 3ltr V6 5spd manual, towing a tandem trailer that weighs 750kg empty, and up to 1000kg when loaded. Once out of town and up to speed (90-110 kmh) it pulls quite fine in 5th.

Beigewagon.
Click to expand...

The issue is not that it won't pull in 5th, but that (according to some folk) towing in 5th under any circumstances will cause major damage to the gearbox.
 
Ashpool,

I understand, but over 400,000kms with a fair amount of towing of various trailers, using 5th hasent destroyed the gearbox, or 5th.

I blew 4th gear, but that was after drowning the gearbox in a water crossing gone wrong.

The work ute has over 120,000kms. all of of it towing a trailer, and so far, no gearbox issues.

Beigewagon.
 
Beigewagon said:
Ashpool,

I understand, but over 400,000kms with a fair amount of towing of various trailers, using 5th hasent destroyed the gearbox, or 5th.

I blew 4th gear, but that was after drowning the gearbox in a water crossing gone wrong.

The work ute has over 120,000kms. all of of it towing a trailer, and so far, no gearbox issues.

Beigewagon.
Click to expand...

Thanks - that's the sort of real-world feedback I've been looking for.

My suspicion is that the issues arise from people who tow without any adjustment to their driving technique and lack mechanical empathy.

Just because you can lug up a hill in 5th doesn't mean you should...
 
Generally it is not the engine that is the issue, it is the Overdrive that is the issue. In overdrive. The gearbox output shaft is rotating faster than the original engine speed in overdrive. 4th gear is usually direct drive or very close to it. With this the engine takes a beating when pulling a load, and engine assisted breaking is useless. The transmission itself doesnt really care what is happening internally. Also on the smllest inclines with a full load you can quickly bog the engine. Towing in OD can cause you to have to shift more (or the transmission if an auto) cause wear issues on the clutches and engine, and (if one is concerned) kill the gas milage.

In an auto you cant even feel the car coming an and out torque converter lockup. The Lockup TC take a huge beating and die an early death. You will also overheat the tranny fluid.

On a manual I would suggest just feel it out. If you feel like you are shifting way more you do unloaded in and out of top gear, then stay in 4th. If the engine is lugging more then it should stay in 4th.

Low RPMS for an engine that is towing is not a good thing. Low rpms and you shifting twice as much as is usually needed is not a good thing for either of you.
 
You must log in or register to reply here.
Back
Top