I have a stock 2005 3500 4x4 QC LWB G56. The only modifications I've made so far are gauges and tires. I have the pyro mounted in the downtube just prior to entering the turbo.

I'm in Nampa, ID and headed up to McCall there is a pretty good grade outside of Horseshoe Bend, I want to says there are parts it is a 7% grade and goes on for a few miles.

Last year I had a 2002 27ft FW toy hauler and used 285/70 Toyo AT's. I never actually measured the weight of the trailer but I'm guessing it was around 7500lbs loaded. For the most part if I caught enough steam at the bottom I could keep 5th gear and the turbo was singing up around 1300 deg and kept around 50mph.

Fast forward to now, I have a new trailer and new tires. I have a 2007 Desert Fox TT toy hauler, I crossed the scales just before the hill with 4600llb steer, 4000 lbs drive, and 8400 lbs trailer. I've also upgraded to new Toyo 295/70 MT's.

I never tried the old trailer on the new tires or new trailer on the old tires so I can't compare those. But I noticed this time going up the hill I didn't have as much umph as before. Headed north, I could keep it in 5th for part of the way before hitting 4th, I kept my temps in check. Headed south which is steeper, I pretty much kept it in 4th with a few jumps into 5th. I think it was around 35-40 uncorrected up the hill headed south. I never had the temps over 1300 but did back down to the 1000-1100 mark as my turbo started whining a little higher than I thought it should.

I'm guessing that my lack of power has to do with the tires and the lack of any other mods to add some hp back into the truck? On the flats and slight grades I seem to be be okay.

I've got a Nelson exhaust that I will be adding shortly and will be opening up the air box. I'm guessing those will help, but I'm thinking that a Smarty would help to.

I wanted to see if I was on the right track. I didn't think that the difference in weight or tires would make that much difference but it sure seemed to. I'm thinking at 8500 lbs should be pretty doable for these trucks without too many mods.

Thanks,
Josh

 

Not sure if this helps, but I run close to 3k rpm when going up steep grades, and my EGT's stay a lot lower then when running the rpm just a little over 2k. It also feels like it has much more power with the rpm higher.

When running higher rpm, my boost guage reads well over 30 pounds (over 40 on one hill), and the EGTs are about 1100 or so. When my rpm was near 2k, the boost would be about 25 pounds and the EGTs would hit 1300 right away.

I recommend running higher rpm for higher boost and cooler EGTs. I hope this helps.

 

There are allot of things that could account for the change in performance. You changed trailers, the new one could be taller, heavier, wider increasing the drag. Since you didn't have a weight on the old one the difference could be considerable. You could have been facing a head wind this time or had a tail wind the last. Your fuel filter could be a little dirty, the ambient air temperature could be higher, etc. The tire height would be negligible in my opinion.

 

Can you clarify this? If your pyro is in the downpipe for the exhaust your temps are reading lower than they really are.

 

For towing!

 

Differnt tires will change your final gear ratio. Taller means higher final gear ratio, smaller means lower final gear ratio. I had a link at one time with a little app that you can plug in your rear gear ratio, then plug in your tire height and get a final ratio. It's awful habndy when tire shopping. i'll have to see if I can find it again.

What's ratio is on your sticker?

 

The thermocouple is right at the base of the collector above the turbo entry so it should be pretty accurate, I don't have it post turbo.

The tires are LT295/70R17's.

Yah I really wish I had the weight on the trailer before but I guess that is the way things, go, it was a fairly warm day so that may have impacted it and I am due for a fuel filter change.

 

I run up the same hill on my way to Stanley with my 10k TT. Going North, I'm usually able to do 55-60 unless some moron cuts in front of me and makes me lose my momentum. Going South, I'm still around 50, but I'm running about 3k rpms. That's a steep hill ( 7% grade )!!!

 

The 295s are about 50% heavier than the stock tires.,not to mention taller. The 295s on my truck made a huge difference in how my truck tows.

I towed my fifth wheel (11,000lbs) all over the NW for two years while I had Nitto 285s on my truck. I put Toyo 295s on last fall and immediately felt a drastic difference in pulling power.

So much so,that I went back to the stock size for pulling my trailer.

I'll run the 295s from September through March and the stock size from April through August.

After I burn through both sets I'll go back to a set of 285s as a nice compromise. They look pretty good and don't make a huge dent in pulling power.

I can't believe the guys that have 35s and 37s and claim to pull 10,000+ lbs like its no big deal. Their towing expectations and mine must be two different things.

 

I've dealt with show pony big tire toy haulers for so long that we still have a set of stock wheels with some 265 tires mounted up ready and waiting for that "my truck has no power towing" complaint that often comes in after the big tire/lift kit treatment. Couple hundred rpm makes quite a bit of difference it the towing world with a Cummins not to mention the already mentioned weight of the tire itself. If you are stuck with your "man" size tire the best compromise I've found with customer feedback is installing a Gear Vendor. Chips/downloaders will also "help" in the short term, but can bite the hand that feeds them with large repair bills. Not always.....but keep it in mind.

 

Good point about the weight of the tires. Those on stock steel wheels I'm sure are heavy. I'm planning on some H2 rims and I think those are lighter than the stock steel ones.

I got my muffler on this weekend and I have noticed a difference just driving around town. I'm taking the trailer out this weekend, but on different hills, still long and steep, but I'm curious to see if it makes an impact.

Once I get a little more cash I'm gonna get a Smarty, so see what type of an impact that has.

But lots of good info.

 

Taller tires on my 97 made me lose a gear on the hills. On the flats it's great. I dont mind the loss it still pulls fast enough.

 

I tow with 35's and there is a huge difference between these and stock! But I'm fine with it - I'm not trying to set any speed records going up those hills. 10k is heavy no matter how you look at it.

 

Once again you and I meet on common ground seen a guy pulling a big big bumper pull camper with a huge lift the truck looked like a stupid half ton pulling that weight wit the nose in the air and the constant swaying. I passed him with a load of cows and he could not keep up with his fancy new truck and my old ranch truck. Ditch the tires get back to or close to stock and see what happens these trucks were made for pulling a load with normal sized tires try it some time

 

You Sir have the Cummins of all Cummins IMHO ...... My 2001 HO 6spd was the best truck I have ever had for pulling...........I agree with the tire issue.....295's are a little to big if you are going to be running up and down the road with a 5th wheel in tow....... I always ran 275's on my 01 with no issues......Boost