New 5th wheel

Josh154

Active member
Sep 28, 2015
1,179
20
38
Sioux Falls SD
Hey guys, just got a 36’ toy hauler 5th wheel. I’m new to 5th wheels, and towing some bigger stuff like this. Hoping James can pop in and give me some insight.

As some of you know my 2016 lml just went through some big changes. Current air & fuel setup are 66 stage 3 in valley with 480 feeding it. 200% injectors and dual pumps.

Im concerned about fuel and oil temps. Are lml oil coolers enough to stay in check with compounds? What about fuel temps? I’ve seen people putting fuel coolers in on return side especially with dual pumps. I’ll be running high rail pressure towing with 2 pumps and don’t want to melt my tank.

Coolant temps should be good with a lml?

My base tune is 850uS and about 750hp. I can’t go any smaller really. I know my foot is the big limiting factor here and not trying to power through all the hills etc.

I’ll attach 5th wheel specs. Trucks on 22x10 wheels with 33x12.5 ridge grappler 12 plys. I just ordered some timbren progressive rate bump stops to try out. I’ve had air bags before and didn’t care for them, hopefully these will do good. If not I’ll ditch for bags.

Hitch setup. Should I go with a slider or stationary? My dad is manager at rv store and getting me cost on either setup I want. Truck is standard bed.

Thanks for the help, and if you have any other recommendations I would appreciate it!
 

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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,812
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83
Phoenix Az
Hey guys, just got a 36’ toy hauler 5th wheel. I’m new to 5th wheels, and towing some bigger stuff like this. Hoping James can pop in and give me some insight.

As some of you know my 2016 lml just went through some big changes. Current air & fuel setup are 66 stage 3 in valley with 480 feeding it. 200% injectors and dual pumps.

Im concerned about fuel and oil temps. Are lml oil coolers enough to stay in check with compounds? No, same cooler 01-16. get a 2020 oil cooler but im willing to bet you will still need an external if you pull big hills in 100*+ days. What about fuel temps? Log them and see what you are hitting. id also ask your tuner if he has adjusted any of the fuel temp limiting tables. if he did, id put them back to stock till you finish logging and can see if you need a cooler. I’ve seen people putting fuel coolers in on return side especially with dual pumps. I’ll be running high rail pressure towing with 2 pumps and don’t want to melt my tank.

Coolant temps should be good with a lml? depends on outside air temps, hills and right foot. "should be" as i dont hear alot of temp issues out of LML even towing on decent power. dont take this to heart though.

My base tune is 850uS and about 750hp. I can’t go any smaller really. I know my foot is the big limiting factor here and not trying to power through all the hills etc.

I’ll attach 5th wheel specs. Trucks on 22x10 wheels with 33x12.5 ridge grappler 12 plys. I just ordered some timbren progressive rate bump stops to try out. I’ve had air bags before and didn’t care for them, hopefully these will do good. If not I’ll ditch for bags.

Hitch setup. Should I go with a slider or stationary? My dad is manager at rv store and getting me cost on either setup I want. Truck is standard bed. Hitch depends on the trailer and if you want to worry about punching out the back window. if the trailer mfg designed it to have a little longer hitch area (less trailer overhang of the hitch) you can get by with a standard hitch but you wont be able to go 90* even on the best trailers. if you do alot of backing into tight spaces where you need that swing, get a slider. i can say that 90% of short bed owners have a slider. There is one that makes a cool slider hitch that automatically slides back as you back up. its kind of a bitch to hook up to if you dont nail getting the pin lined right up with the hitch but its nice not to have to get out and move the hitch each time. This is where i love my long bed

Thanks for the help, and if you have any other recommendations I would appreciate it!
See all my notes in the quote in red.
 

Josh154

Active member
Sep 28, 2015
1,179
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38
Sioux Falls SD
Thanks James! Just picked up this hitch. I’m assuming this is the one you’re talking about? Demco 21k auto slide. 365E2749-1C78-4733-B7D3-70CEBDF31865.jpeg

Also it sounds like a fuel cooler on the return side is a must on lml’s. Cp4 didn’t return as much fuel therefore gm didn’t have the fuel cooling side as beefed up. A guy I was talking too was seeing 180-190 with a 10mm cp3 only. With duals I’m sure I will see more then that.

What are you running for a oil temp sensor? Does this thread into oil filter housing? Sounds like l5p oil cooler will be next on list, and go from there wether I need a external or not.

Will a flash temp sensor on oil pan give me a good idea of oil temp or will that be inaccurate? What’s safe oil temps and when I should pull off and let things cool down?
 

jlawles2

Member
Jan 27, 2010
948
2
18
Danbury, TX
That's a good slider, I have a different auto one. Watch when you set it up that the king pin is over the rear axle or slightly forward because it will pull load off the steering axle (min is currently setup incorrectly by the dealer who sold it to me).

Find the manual, read what to lubricate (dry lube only for me), and you will probably need to grease the top plate of the hitch regardless of what the manual says. Paint acts like glue, even though its not rotating and needing grease for that, you have to slide up on it for making the connection.

I watched a lot of videos and read manuals, then figured it out myself that hitching works best if you aim for 1"-2" of suspension compression as the truck takes load. To unhitch, I watch the suspension and aim for that same 1"-2" of suspension unloading. That's what works for me.
 

Josh154

Active member
Sep 28, 2015
1,179
20
38
Sioux Falls SD
I was wondering where to mount the bed rails. Basically I was thinking clip it in the rails, make sure pin is slightly in front of axle, drill holes and bolt it up.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
17,812
255
83
Phoenix Az
Thanks James! Just picked up this hitch. I’m assuming this is the one you’re talking about? Demco 21k auto slide. View attachment 105590

Also it sounds like a fuel cooler on the return side is a must on lml’s. Cp4 didn’t return as much fuel therefore gm didn’t have the fuel cooling side as beefed up. A guy I was talking too was seeing 180-190 with a 10mm cp3 only. With duals I’m sure I will see more then that.

What are you running for a oil temp sensor? Does this thread into oil filter housing? Sounds like l5p oil cooler will be next on list, and go from there wether I need a external or not.

Will a flash temp sensor on oil pan give me a good idea of oil temp or will that be inaccurate? What’s safe oil temps and when I should pull off and let things cool down?
yup, thats the slider!

yes there is no fuel cooler on the LML's. adding one will only help. put the best cooler and fan on you can afford (stacked plate style cooler and highest cfm rated fan that covers the cooler).

i had always ran an autometer gauge and sensor in the old truck. new truck uses an algorythem thats pretty good. Get a 2020 oil cooler, not a 17-19 oil cooler. i prefer a sensor in the oil cooler (iirc its the top plug as that is pre cooler and just after the pump) since this is where most guys are basing their temp info from. dong it else where can skew comparable numbers.

as for temp, if you run a synthetic oil, i wouldnt worry too much in the 270-280 range. Oil pressure will be more your issue there. if you start dropping under 40 psi at over 2k rpm, id be letting out. Compare your oil temp to that pressure so you know at what temp you should be pulling back. if you are running reg conventional oil, id try to keep it at or under 250-260*. at those temps, it starts degrading the oil pretty quick. Its not like the oil will be shot by hitting that temp one time but hitting that temp many times over the next 3k miles is what does it in.

to be honest, if your oil temp is getting that high, ill be your coolant temp starts hitting 230-240*. Ive noticed a trend with my old truck and other trucks that when the oil cooling starts to become efficient through the factory cooling system, coolant temp starts to follow oil temp closer. You having a better cooling stack will help the truck take advantage of the 2020 oil cooler as the cooling system will be able to take the additional heat load better.
 

Josh154

Active member
Sep 28, 2015
1,179
20
38
Sioux Falls SD
Thanks James!

I do run t6 synthetic. Honestly I’ve never seen my coolant temp above 190 on the lml lol. I’ve seen 210 on the old lmm. This is currently towing my 16’ enclosed about 7,000lbs.
E435BF7D-42A5-4631-8CE2-8A3770EC13E8.png

I’m definitely going to purchase a derale cooler for fuel and swap that 2020 oil cooler on and throw a probe in it at same time.

I’ll be pulling the 5th wheel this weekend about a hour and half away. Nothing too crazy yet but will be a good test to monitor some stuff!
 

Josh154

Active member
Sep 28, 2015
1,179
20
38
Sioux Falls SD
Lol I’ll have one this weekend. Buying it from father in law, it’s a 06 raptor. Nothing to fancy but gotta start somewhere! I grew up racing dirt bikes and gonna start the tradition with my son now too. Little man is 3 months
 

NevadaLLY

Adam B
Feb 24, 2019
145
3
18
Reno, NV
I moved away from the massive slider BMW hitch and now use an Anderson. Some hate it, but I love it. Way less weight in the bed and cleans everything up. It also can be taken in and out in seconds and you can essentially hook it up at any off angle. Most toy haulers see some dirt time and we aren’t always level so it’s nice not to mess with it. About 10 buddies all use Anderson and are happy with it. If you have the gooseneck ball, you don’t have to add any rails with Anderson. I also use the trail-air pin box which makes things ride nice and smooth.

Fort your power level, towing at 750 will have its challenges. Just don’t try to keep the speed limit over grades. Will your truck do it? Probably. But I’d guess temps start climbing quickly.

On your bed loading, I’d go with airbags and onboard compressor. I love mine and wouldn’t go any other way.
 

Josh154

Active member
Sep 28, 2015
1,179
20
38
Sioux Falls SD
Here’s the camper. Didn’t get finished installing hitch in my truck so taking the father in laws 2020. Messed around cleaning carb and all that fun stuff on generator. Campers been sitting for 2 years so had a lot to get ready. Just doing a small camping trip this weekend but can figure out what bugs I need to work out and finish getting the duramax ready!
 

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Pure Diesel

Randsburg Drifter
Apr 22, 2008
740
10
18
So. Cal.
Nice looking toy hauler. What size is the garage on that triple? Run & keep Sea Foam in the fuel for the genny. Good luck with the first trip and enjoy.
 

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