I'm Wondering............
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Senior User
Joined: Oct 2005
Posts: 309
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I'm Wondering............
how long you could run on the hiway in 4-lo, hubs unlocked???
I've been caught before in long slow crawls up 3 or 4 miles of grade while towing the trailer (15k) and had the tranny get pretty warm due to insufficient air passing through the coolers.
So, how long at 35mph could I travel up the mountain, towing, in 4-lo before damaging the transfer case?? Or would damage ocurr?
Seems like the higher rpms, although at 30-35 mph, while geared down so much, would allow a longer pull before heating up the tranny due to low airflow.
But, I dunno, so..............................
I've been caught before in long slow crawls up 3 or 4 miles of grade while towing the trailer (15k) and had the tranny get pretty warm due to insufficient air passing through the coolers.
So, how long at 35mph could I travel up the mountain, towing, in 4-lo before damaging the transfer case?? Or would damage ocurr?
Seems like the higher rpms, although at 30-35 mph, while geared down so much, would allow a longer pull before heating up the tranny due to low airflow.
But, I dunno, so..............................
Laughing Gas
Joined: Aug 2009
Posts: 1,192
Likes: 7
From: Belgrade, MT
Tranny cooler
Might want to consider upgrading your tranny cooler. One from a 6.0 is a good upgrade. I have a derale I got from Clay that I am hoping to install inline with my factory one this weekend providing weather and wife allow the time. I will post pics and results when done.
Hook it, I'll pull it.
Joined: May 2007
Posts: 15,037
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From: Grand Lake, La.
I don't see a problem with that, but I would unplug the solenoid on the passenger firewall so the front hubs don't lock. As long as you are not turning to many RPM's I don't see a problem. Just remember, you have to stop to put it back in 4 hi. That could be a problem when traffic starts moving at a good clip. Keep an eye on the gauges. lol
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No, bigger cooler does no good when theres no air flowing thru it.
Thanks Rick. Manual hubs, so no problemo. Thought maybe the higher revs to maintain 30-35 would result in a wash as far as higher egts.
Rick
Thanks Rick. Manual hubs, so no problemo. Thought maybe the higher revs to maintain 30-35 would result in a wash as far as higher egts.
Rick
Posting Guru
Joined: May 2006
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From: Milroy, PA
Actually, a bigger cooler does cool better ALL the time. While your slow crawling, your engine fan is still drawing air through the front of your truck. Make the surface area of the cooler as big as the 6 liter, or v-10 cooler, and you will see a difference. If you ever compared the difference in size between either of those, versus the origional 7.3 tranny cooler you would understand. If you run in 2low, you raise rpms, also increasing air through the front of the truck, through the cooler. Running in 2low is not a problem. The gear reduction is through a set of planetary gears.
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From: Payson, AZ
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Senior User
Joined: Oct 2005
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Ergo, gear down even farther in 2-lo, reduce egts, and mollify the lack of air through the coolers with lower engine temps.
Cargo Master
Joined: Mar 2006
Posts: 2,502
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From: Bend Oregon
I've done it, 4 low pulling about 14K up cabbage hill aka emigrant pass aka deadman pass on I84 in eastern Oregon at around 30mph with no ill effects.
That hill is nasty....2000 ft in six miles with 2 switchbacks on 6% grade.
EGT's are real low because your not really working the engine with the gear reduction. At those speeds on a hill the right lane is usually clogged with OTR trucks so running out of gear usually isn't a problem and there is almost always a break check at the top so you can stop and put it back in 2HI for the trip down.
That hill is nasty....2000 ft in six miles with 2 switchbacks on 6% grade.
EGT's are real low because your not really working the engine with the gear reduction. At those speeds on a hill the right lane is usually clogged with OTR trucks so running out of gear usually isn't a problem and there is almost always a break check at the top so you can stop and put it back in 2HI for the trip down.
Posting Guru
Joined: Feb 2004
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From: IOWA
A bigger cooler will help, and in the long run it'll definitely pay off. I have a larger tranny pan along with a 6.0L cooler and pulling heavy loads slowly I still struggle to get it over 150*.
The biggest thing I found to help is a TC lockup switch. The majority of your heat at low temps is from the TC slipping, if you're able to lock it up it'll make a big difference in temps. I've watched my temps go down after I lock it up.
I think there's a select few around here that have towed heavy loads slowly. It's a lot harder than one thinks, exactly because of the point you're bringing up. You don't have the air flow through the front end to keep things cool, so you have to manage other ways to keep things in line.
Good luck!
Logistics Pro
Joined: Jul 2009
Posts: 3,635
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From: Lansdale, PA
I will be adding ducting/sealing all the gaps betweeen the front of the truck to the radiator. that way all the air HAS to go through it all. Bigger trans cooler for sure will always help. My 93 explorer, truck trailer and load tipped the scales at 11,200lbs, got used in low range a lot. I would drive it all around in low range, no issues at all with wrecking the transfercase. Throw a temp gauge in the bottom drain plug and see what the temps get to. If they dont go up then no worries, if they get hotter then 220 then id be concerned.
Posting Guru
Joined: Jul 2004
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From: Kamloops, BC
I do it all the time ! In 2low the trans locks up way better because you are running in 3rd or sometime OD and doing the same speed and you would be in 2nd in 2HI, but in 2nd 2HI your trans is slipping a lot more !
Try it... you will be happy with the results !
Try it... you will be happy with the results !
Posting Guru
Joined: May 2006
Posts: 2,274
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From: Milroy, PA
Not necessarily true, your fan may be turning but it doesn't mean it's drawing air. You can tell when the clutch kicks in because it starts making a big whooshing noise, but that is only when the engine temps get warm enough.
A bigger cooler will help, and in the long run it'll definitely pay off. I have a larger tranny pan along with a 6.0L cooler and pulling heavy loads slowly I still struggle to get it over 150*.
The biggest thing I found to help is a TC lockup switch. The majority of your heat at low temps is from the TC slipping, if you're able to lock it up it'll make a big difference in temps. I've watched my temps go down after I lock it up.
I think there's a select few around here that have towed heavy loads slowly. It's a lot harder than one thinks, exactly because of the point you're bringing up. You don't have the air flow through the front end to keep things cool, so you have to manage other ways to keep things in line.
Good luck!
A bigger cooler will help, and in the long run it'll definitely pay off. I have a larger tranny pan along with a 6.0L cooler and pulling heavy loads slowly I still struggle to get it over 150*.
The biggest thing I found to help is a TC lockup switch. The majority of your heat at low temps is from the TC slipping, if you're able to lock it up it'll make a big difference in temps. I've watched my temps go down after I lock it up.
I think there's a select few around here that have towed heavy loads slowly. It's a lot harder than one thinks, exactly because of the point you're bringing up. You don't have the air flow through the front end to keep things cool, so you have to manage other ways to keep things in line.
Good luck!