HDJ81 Towing Underwhelming...

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Nov 22, 2007
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Quesnel, BC
As I look toward a new camping season I've started thinking about the underwhelming performance my 1990 HDJ81 has towing my 21ft aerodynamic 3000lbs travel trailer. I used to tow this trailer with my '99 4 Runner V6, and to be honest I wish my new old rig could do as well with it. It has 33" tires, stock exhaust, the largest tranny cooler I could get, new fluids, and recent tune up. The power delivery is fine...though I'm going slower now and watch my RPM's a lot closer than I did in my 4R. My biggest problem is with the tranny temp. Going no faster than 80 or 90 km/h, easing it up to speed to get the tranny locked (over 60km/h I think), I regularly get the tranny overheat light coming on going up hills. I have to pull over and cool down before I even attempt anything big. This is driving on routes like hwy 97 from the Okanagan Valley to Prince George (BC), where there are a few hills, but no epic passes like the Coquihalla. I went to a tranny shop and they smelled my oil, and I haven't burnt it, but it makes me a little nervous, and discouraged to really use it for any major trips. It seems on this forum, people are towing all sorts of things with their rigs and little reference to this problem. The truck is great otherwise...I love it. Any suggestions?
 

e9999

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get a trans temp gauge to avoid damage until it's fixed if you're going to drive more

if the engine is not getting too hot (do you know for sure?), seems like there is perhaps something wrong with the trans itself? Is the fluid actually circulating well through the cooler?

on the improbable side, but I gotta ask: you don't have stuck brakes or bad bearings on the trailer by remote chance? although they'd probably be red hot and dead by now... :)
 

Lka1988

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I have a hard time believing a 3.slow 4Runner can out-tow a diesel. Just a hunch, you know.

I'd make sure your diesel is in good shape... The early Cummins 6BTs only put out 150 hp/300 lb-ft or so, they have no problems towing 3000# trailers.
 

IdahoDoug

 
 
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Makes me immediately suspect your cooling system, frankly. I don't know any details about the tranny cooler you installed, but I do know that when a factory tranny pump is spec'd it is matched with the flow characteristics of the factory cooler that is engineered with it. Slap on one that's got smaller openings which slow the flow or create a pressure situation and voila - you've slowed the fluid and allowed it to get more heat at the sensor for the guage. Or worse, the fluid is actually running hotter everywhere because of either slowing or speeding the fluid versus what the factory intended. You can flow fluid FASTER through a cooler and get LESS cooling as well.

So, I'd look at the cooler and other aspects of the cooling system such as the radiator possibly being plugged and or the rad fan clutch being old, etc.

Importantly, did you tow BEFORE adding the cooler, and what happened then?

I think something is awry with the cooling system.

DougM
 

80t0ylc

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Personally, I think your biggest enemy is the 33" tires. Iknow - I know, they help off road but, when you're towing more than a light utility trailer, you need all the help you can get. Sometimes it's just fractions of an inch or a few pounds or a couple of degrees that are the difference. Re gear or have a stock set of tires/wheels for towing. My .02
 

Cruisin'

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I have been towing a 18' 3,500lb + travel trailer with my HDJ81 with no problems. I installed a Tru-Cool LPD4589 cooler, and have never had the tranny light come on, even pulling the Salmo-Creston pass (What a b**** of a hill!) I am running stock size tires which may make a difference. Like has been said before I would look into the cooling system and make sure everything is up to snuff.
 
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You could also crank up your fuel a little too. I dont know how, but if you search the diesel group they do.

Karl
 
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I have a hard time believing a 3.slow 4Runner can out-tow a diesel. Just a hunch, you know.

I'd make sure your diesel is in good shape... The early Cummins 6BTs only put out 150 hp/300 lb-ft or so, they have no problems towing 3000# trailers.

  1. 99 4Runner so a 3.4 V6.
  2. Try 160/400 for the Dodge version rotary pump engines.
I have towed a much heavier trailer with stock gears, 6" lift and 35" tyres with no issues so I suspect that you have some sort of mechanical fault with yours...
 
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fwiw I have towed my 3000lb tent trailer with a load of bikes and kayaks on the cruisers roof and five passengers with my stock gearing and 285 mt's using the stock tranny cooler and not had any cooling/overheating issues.
 
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well 3k pounds is 1.3 tonnes. that really isnt alot. is your 80 a jap import? I ask because i've heard stories about how they are treated servicing wise. Really the trans shouldn't be overheating even with that load. And the motor should make mince meat of any hill.

I would start with a reputable diesel injection shop. the injector servicing on a direct injection motor is always important. (more so than the naturally aspirtated - indirect injection versions) from there they can look at the boost, if it's making what it should, and the fueling etc. I wouldn't go raising boost/fueling beyond stock specs if the motor isn't making standard power.

Do you know the sulfur content of the local diesel? a 90 model unlikely has low sulfur friendly seals, unless it has been rebuilt recently. This could also affect performance.

Does the exhaust blow alot of black (or other coloured) smoke? Black smoke is just wasted ponies going out the exhaust and a good indicator of a problem.
 
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Just to confirm, there must be something wrong. I regularly tow 7000 pounds on fairly long journeys and have never had any issues.

I recently drove 600 miles with the rig below (prob 6500ish) and apart from the steepest hills here in the Scottish highlands never really dropped below 60mph.

My first thoughts would be to put the stock cooler back on...

Jamie
 
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e9999

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Just to confirm, there must be something wrong. I regularly tow 7000 pounds on fairly long journeys and have never had any issues.

I recently drove 600 miles with the rig below (prob 6500ish) and apart from the steepest hills here in the Scottish highlands never really dropped below 60mph.

My first thoughts would be to put the stock cooler back on...

Jamie
:)
well, there goes the natural hierarchy for those 2 vehicles... :D
 
Joined
Nov 22, 2007
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Quesnel, BC
get a trans temp gauge to avoid damage until it's fixed if you're going to drive more

if the engine is not getting too hot (do you know for sure?), seems like there is perhaps something wrong with the trans itself? Is the fluid actually circulating well through the cooler?

on the improbable side, but I gotta ask: you don't have stuck brakes or bad bearings on the trailer by remote chance? although they'd probably be red hot and dead by now... :)
Good idea on the tranny temp gauge! The trailer is good though...it's definitely the LC...
 
Joined
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Quesnel, BC
Makes me immediately suspect your cooling system, frankly. I don't know any details about the tranny cooler you installed, but I do know that when a factory tranny pump is spec'd it is matched with the flow characteristics of the factory cooler that is engineered with it. Slap on one that's got smaller openings which slow the flow or create a pressure situation and voila - you've slowed the fluid and allowed it to get more heat at the sensor for the guage. Or worse, the fluid is actually running hotter everywhere because of either slowing or speeding the fluid versus what the factory intended. You can flow fluid FASTER through a cooler and get LESS cooling as well.

So, I'd look at the cooler and other aspects of the cooling system such as the radiator possibly being plugged and or the rad fan clutch being old, etc.

Importantly, did you tow BEFORE adding the cooler, and what happened then?

I think something is awry with the cooling system.

DougM
Good ideas...thanks! I'll poke around some more with this. I had the cooler installed at ATEB (reputable with 81's) before I even picked it up for the first time, so I have no before / after comparison.
 
Joined
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well 3k pounds is 1.3 tonnes. that really isnt alot. is your 80 a jap import? I ask because i've heard stories about how they are treated servicing wise. Really the trans shouldn't be overheating even with that load. And the motor should make mince meat of any hill.

I would start with a reputable diesel injection shop. the injector servicing on a direct injection motor is always important. (more so than the naturally aspirtated - indirect injection versions) from there they can look at the boost, if it's making what it should, and the fueling etc. I wouldn't go raising boost/fueling beyond stock specs if the motor isn't making standard power.

Do you know the sulfur content of the local diesel? a 90 model unlikely has low sulfur friendly seals, unless it has been rebuilt recently. This could also affect performance.

Does the exhaust blow alot of black (or other coloured) smoke? Black smoke is just wasted ponies going out the exhaust and a good indicator of a problem.
Good ideas! It is a JDM import, but the folks at ATEB were impressed with the condition of it relative to all the other ones they have seen come through... they seem to think it's performance is about on par with how it's supposed to be. The engine performs well, aside from what I think is a lack of power...a little smoke only when I start it or goose it...it seems normal. I can even live with the power...it's not terrible...it's more having to pull over for the tranny temp that is getting me down.
 
Joined
Nov 22, 2007
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Quesnel, BC
Thanks for everyone's help! Definitely sounds like I should be able to expect more from it based on what other people are doing. I will have to poke around a bit, and see what's happening!
 

Tapage

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get a tranny temp ( fit it at the tranny outlet that goes to the front tranny cooler ) and then take a run without the trailer ..

Which it's your outside temp .. ?

Are you using your AC ..?

Are you driving with your OD on .?
 
Joined
Nov 22, 2007
Messages
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Location
Quesnel, BC
get a tranny temp ( fit it at the tranny outlet that goes to the front tranny cooler ) and then take a run without the trailer ..

Which it's your outside temp .. ?

Are you using your AC ..?

Are you driving with your OD on .?
outside temp was 10c, no AC, no OD. A tranny temp guage is definitely on the list now.
 
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