I just picked up a new 34' travel trailer that weighs right at 8000 pounds dry and I'm working on getting my 2000 EX setup for the job. The Ex has a 7.3 and is lifted with 325-60R 20 Nitto Terra Grapplers, the transmission was just rebuilt and I added the 6.0 tranny cooler at that time. It is still running the factory 3.73s in the diffs. The other existing mods are in my signature. My questions are what else do I need to do to get it right to comfortably cruise with no issues.

The list of pending stuff

A pillar gauges, Boost, Pyro & trans temp
Different gears, 4.10s or 4.30s with the lift & 35" tires?
Tuner, DP or something else?
Rear sway bar, Hellwig or F350?
Which air bag setup & why?

I'm sure there will be more later.....

 

The easiest mod is also the one you do not want to hear. Get rid of the oversized tires. They are hurting your torque/RPM curve especially when under load. The sweet spot for the engine and for towing is right at 2000 RPM. Stock tires will give you maximum fuel economy and torque at that RPM, if you can match it with road speed. That road speed is 71 mph. I bet you that at 2000 RPM, you are cranking down the road at 79 mph, which is way too fast for towing the drag chute we all call travel trailers. Get back to stock tire diameter. It is much cheaper than installing new front/rear differentials.

I usually tow in the range of 68 - 72 mph and have pretty good fuel economy (>9.5 mpg) doing so. The "Midas" has enough reserve left to pass a big truck when needed.

 

My math might be wrong, but at 2000 rpms with 35's the indicated speed would be 79-81 but the true speed would be 56mph based on 3.73. Larger tires make less revolutions than smaller tires = less speed.

 

Yep. Math is wrong. Speedo will read 71. Actual road speed will be 79 mph.

 

Regearing will solve that issue, but it's not cheap of course.

I like the Roadmaster Active Suspension or RAS. Helps with stability and gives you a little more weight capacity.

You'll need a brake controller, Prodigy P3 is a big favorite.

And perhaps most importantly a good weight distributing hitch with sway control. Either an Equal-i-zer or Reese straightline for something moderately priced, or if you want to get the best a Hensley or Pro-Pride for $$$$.

 

Thanks Forest. I'll sacrifice, or at least make up for with a tuner, the slight power & mpg loss to keep my lift & tires. I just want to bring the rpms up into that 2000 rpm range in od like you said. I drove it home at about 60 & 2000rpm in drive today.

ExxWhy, thank you too,
I'll check out the RAS. It already had a brake controller when I bought the EX, I'm not sure what kind, but it seemed to work well on the 20 mile trip home. I picked up the Equal-I-Zer hitch with the trailer, I forgot to mention those.

 

Even with the tuner you are still putting a lot of strain on your transmission. even when not towing, and towing is just going to be that much harder on it. when towing it will be as if any trailer you tow weighs 2-3k lbs more than what it actually weighs! You need to change the gears!!!

 

read this thread and compare the chart:


https://www.ford-trucks.com/forums/1...n-gearing.html

 

I have every intention on changing the gears, that's in my original post, just trying to figure the right ratio to go with.

 

Thanks Housedad. 4.30s it is.

 

You could get some stock rims and tires to use when you tow and then you have the best of both worlds!!

 

I wouldn't, not with 35's and a 7.3L PSD.

I have 37's on a 6" lift with 4.30's and it's perfect...spot on. With 35's, 4.30's will be too much.

4.10's would be the most I'd go.

IIRC, Tor went with 4.30's on 35's and he ended up having to re-gear a second time, down to 4.10's.

Stewart

 

If the plan is to pull the trailer in OD, Id say at least 4.30s, you are going to need to make that as easy as possible for your tranny. Although I would suggest not pulling any box trailer in OD to begin with and if thats the route you go 4.10s w/od off.

 

That's a negative ghost rider, the pattern is full.

Only tow with the OD off (for the 4R100) if the trans is gear hunting, like on a grade.

4.30's will be too much with only 35" tires, since he has the 7.3L PSD.

Stewart

 

Yep. 4.10s will get engine RPM back in the 1950 - 2000 RPM range at 70 mph for 35" tires. Note that stock tires are 31.65" OD, yours are calculated to be 35.35" OD. 31.65/35.35 = 0.895. The 35" tire spins 10.5% slower for a given speed. 3.73/4.10 = 0.910. Almost a perfect conversion.