5th Gear & towing

A general rule is dont use 5Th gear under 80Kmhr towing or not towing too much strain on gear box. Had to rebuild plenty of Nissan & Ford courier gearboxes with 5Th gear failure.

The 5th gear problem with the GU Nissans was a design fault. Mine went at about 120k, and I had never towed anything. Nissan fixed it free under the extended warranty, but I understand that they were fixing it anyway if it was out of warranty - as usual with Nissan tho, it just took some pressure to get it done for free. The replacement parts addressed the design fault.
Gerry

Well I can prove to you that a landcruiser auto runs better in 4th when towing.

I have a 3in exhaust and an EGT gauge mounted in the exhaust after Turbo

I tow a 2.8 t van

In 4th on a flat or mildly undulating road the exhaust temp stays around 325 C at 2350 revs or 90kph
If I drop it into 5th or O/D the temp rises to 400C straight away.

Reason being revs drop back to 1800 which means engine is lugging in the gear and therefore working harder to maintain speed.

It therefore also puts added strain onto gearbox and will increase gearbox oil temp as well

Have done 26,000km so far on trip and hardly ever use OD.

Fuel consumption remains about the same and is no worse than those who have posted figures using OD

That is 17kp100km

In view of the above I would never advocate towing in OD despite what the doubters say.

The figures speak for themselves, always remembering that the manifold temp is 200deg hotter than the exhaust and pistons melt at a bit over 700deg.

Its simply not worth the risk.

Cheers

Prove?? 2.8t van! of cause you would leave it out of OD..

My camper is 1.5t as stated and my cruiser is manual.

The question was about damaging the gearbox which generally refers to manual boxes since the autos are generally planetary so don’t have the same inherent weak point that a manual box does.

For the record, my cruiser uses less fuel in 5th even when towing my 1.5T camper. If I were lugging a 2.8t behemoth I to would avoid 5th too.

Fair enough but the same applies . Use low revs and the engine runs hotter.

Just as an aside you say your camper is 1.5t and your rig is 5t

As far as I know the max legal weight of a 100 ser is 3260kg including any ball weight.

I admit you didnt say which ser u have. So.

Mine is right on the limit I weighed it the tow ball weight is 280kg.


Cant get a lot of heavy stuff in if fuel is full.


Cheers

Yep, LC105 at ~3.5t with 260ltrs of fuel and 50ltrs of watr on board. Never was one to stick to the "rules". I'm yet to see a true outback tourer under it's GVM.

I can tow my van in 5th all day long but it's not a very bright thing to do. My mechanic has a 80 series manual cruiser and never, ever tows in 5th and told me the same, even though I was already aware of the issue. You'll get away with it for a while but at any time.............kerchunk

Hasn't happened in the last 300k lol. Did your mechanic offer to sell you a Hiclone too? By the way, not driving your car also saves it wearing out.

Seriously, how big is your van? People need to use their own brains and deside what is acceptable.

Obviously not all fall into that category or there would be no questions on here.

Replys with constructive advice are better than ones that just bag others.

Vans and cars come in all sizes .

People are the same and come in various degrees of skill and awareness.

Thats why they come on here and ask for advice.

If you have none to offer why bother posting.

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Hi Graham H, I find when towing with the 5speed auto, 100s that it won't allow it to lug hard anyway,in OD, changes down and stays comfortable,just have to watch it dosen't start to hunt up and down to much in hilly country, otherwise leave it in 4th, but it changes down again below that the same way ,so most of the time i let mine sort its self out!


cheers Axle.

Well what you do is up to you.

The figures I have posted were taken on just light throttle and even on a flat road applies.

There is a point where the car will travel in OD with not enough boot in it to make it change down.

It will however lug at about 1800-1900 and put the temps up.

I thought the same as you before I put the EGT gauge in and did drive it like that thinking thats what the Auto was for.

Since watching the temps under those same driving conditions I have revised my style to only tow in 4th.

Car is much happier it just sings along it doesnt use any more fuel and I dont have to worry about when to change into 4th.

You would be surprised how hot they get at times.

Coming up from Batemans to Canberra the exhaust temp got up to 500deg near the top of the last long hill.

That is any amount hot enough as the cylinder temp would be close to 700deg.

This is getting very close to sensible limits.

The temp when I drop it into 5th when just cruising climbs up at least 75 deg starting almost instantly and would be up there within a k.

I am firmly convinced for longevity that staying in 4th is is the way to go.

It does of course depend on the weight you are towing but similar figures will be reached.

My rig is just over 6000kg all up fully loaded .

I have been thinking of putting a trasmission temp gauge in as well and may do so yet.

Cheers

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Nice to see you confirm Steves thoughts.

Your prev post said it was Ok to tow in OD and overweight as well

Hardly good advice to anyone

One day your overweight load may also bite you where it hurts.

lol you two need a room.

might be a bit of a misconception here.
The danger from the high exhaust temps is not to the pistons or even valves (unless the high temp is due to a leaky exhaust valve).
It is to the turbo itself.
The proper place for the EGT probe is between the head and turbo but isnt practical in most auto engines.
You are unlikely to damage a piston unless the injector itself is faulty.
Remember pistons have cooling sprays to remove heat from that area.

Maybe so but if as you say pistons have cooling sprays why do Nissan 3.0ltr

burn holes in pistons .

Overboost has a part in it causing higher temps and hence burnt pistons isnt it

I know that the sensor is better before turbo but at a cost of several hundred dollars to get it there its cheaper to have it in exhaust and allow 200deg.

Presumably as the exhaust gas comes from the cylinders, if it is hotter then the internal cylinder temp would also be hotter as it cant get hotter after leaving cylinder can it??????.

If your exhaust temp gets over 500deg its time to back off in my book.


Cheers

You didn't just disagree with the locals, did you??

"Maybe so but if as you say pistons have cooling sprays why do Nissan 3.0ltr

burn holes in pistons ."

story was that one of the piston cooling nozzles was being moved slightly during assembly on #1 (I think) cylinder on some engines.

"Overboost has a part in it causing higher temps and hence burnt pistons isnt it"

This is something different again. To do with variable vane turbos and overfueling, but as Im not a Nissan owner I havent paid much attention to this. Im assuming you are referring to the ZD30 again here?

"Presumably as the exhaust gas comes from the cylinders, if it is hotter then the internal cylinder temp would also be hotter as it cant get hotter after leaving cylinder can it??????."

Yes it can and does, for several reasons.
One is a burnt exhaust valve. Another is overfueling or dodgy injector, fuel still burning when firing stroke complete/exhaust valve open.

Probably 500deg is a safe number to use, though a turbo/fuel injection expert would know better.

Graham you're talking about lugging the 1HD-FTE at 90kph, 1800-1900rpm trying to pull 6t. Of course the EGT will rise in top because it hasnt hit its most efficient power/torque band. For those pulling less weight at 100kph towing in 5th will be much easier on this engine.

I really thought that was exactly the point I was making wasnt it.

Even at 100 kph the temp rises in O/D.

As I dont have a lighter van I cant compare.

With my own experience I would not recommend using O/D to tow any

significant weight anywhere ever.

It is meant as a fuel saving cruising gear not as a towing gear and several posts

on here agree.

One obviously didnt but he doesnt believe in weight limits either so advice

must be taken with caution.

I understand Nissans blew holes in No 4 and sometimes No 3.

Yep, don't listen to me, my cruiser runs a few kg too heavy when the tanks are full. oh my god! I must be insane.. god help the world lol.

"I understand Nissans blew holes in No 4 and sometimes No 3."

Probably, I did say I wasnt sure which as Im not a Nissan owner. Nor am I likely to be.

Still the premise of this thread was regarding strength of 5 speed boxes for towing re: 5th gear so this has been sidetracked a bit. Auto's dont have the same issue with strength of 5 gear

Ford Ranger manual also says dont tow in OD. I follow the manual with my tray top camper and boat in tow.

Just a word of warning here

A good bit of advice is the truckies creed.

Use the same gear down hill as you did going up.

Saves runaways in trucks and overheating brakes in lighter vehicles.

If I dont know the road and it looks a bit of a long hill or steepish I keep it in a

lower gear until Im sure of the road.

Whacking it into O/D at the top of a hill can be a recipe for disaster.

Cheers

Muzbry - I agree "If the engine labours, you are in the wrong gear"

All cars are different though, 2000rpm in mine is cruising in 5th Gear at 100ks. It has enough power to tow my boat up some hills still sitting in 5th on 100ks and that is where the problem is, the gear is not strong enough for the cars power.

So advice is still to tow in 4th when strain is starting to increase on 5th. Cheers

Basically what I said

If the motor isn't in its torque zone its labouring and therefore gets hotter as I posted.

If its overloaded it will get even hotter.

Some don't realize the importance of correct revs for any given speed.

Anyway travelling at excessive speeds with trailer of an appreciable size is not

advisable as its not always how easy it is to go fast, its the ability of how you

can stop it that often is what matters.

That's what keeps me to a sensible speed anyway.

while that may be the case with the Mitsi, in the hiluxes the problem is that 5th is on the opposite side of the carrier plate and not supported on both sides of 5th, just a bearing on inner end. Shaft shears off flush and cog drops to bottom so 5th no longer exists.
But the V6 box which fits in the same place has a bearing on each side.

Most boxes use needle rollers AFAIK with no probs.

What do pages 29 and 30 say apart from the above.