GMC rear end gear change?

[Jlwright]

that sounds encouraging.

[rnkburg]

I did a swap on my cummins and best thing I ever did for the truck. I had 3.55 and went to 4.11. People said I would hate it but it gives me two ranges to choose from. With stock tires I can run 4.11 and with my 35's it drops to 3.73 ish truck runs easier while towing and although no one will believe me it toes better with the 35" tires on vs the stock size. I have towed my raptor 300 with this and truck pulls like a dream. I mainly tow with my dually but the 3/4 pulls the trailer just fine. I did front and rear swap and ordered parts from Randy's ring and pinion. Great guys to deal with and best prices around that I found. He also has a calculator on there as well.


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[Jlwright]

What effect did it have on fuel mileage? I'm thinking 3.73 gears wouldn't hurt and might even help when pulling the 5er. The rear end gears are not expensive but haven't checked in what is involved to change the transfer case gears.

[Javi]

Originally Posted by Jlwright

What effect did it have on fuel mileage? I'm thinking 3.73 gears wouldn't hurt and might even help when pulling the 5er. The rear end gears are not expensive but haven't checked in what is involved to change the transfer case gears.

You don't change the transfer case gears... you do need to change both the front and rear ring gear and pinion.

[{tpc}]

Originally Posted by Jlwright

I'm thinking you are are right about the six speed transmission and the higher gears. I have only pulled the camper home from the dealer which is about 35 miles with hills and not much flat ground. It seemed to do a lot of shifting which I'm not crazy about. it is just something I'm not used to but will adapt.

Is there a tow haul button on it? Make sure you are using that first of all, and the suggestion to put the trans on M5 to lock out 6th will help as well.

I always use the tow button and I can feel a difference. I used to not put the truck into 3rd (4 speed tranny), because I thought the tow button had control of that as well, but on mine at least, it only changes the shift points. Much less gear "hunting" when in 3rd for me.

On the newer trucks, not sure if the use of cruise control would be advised as well. I played with it once on mine, because I wanted to see what it would do after coming down a small hill and approaching a small grade. It basically acted as if I floored it, dropped it down into second, and tried to keep the speed up when going up the hill. I turned it off after a short time, but even that sort amount got the tranny hotter. Not dangerously hot or anything, but hearing the truck trying to wind out like that pulling up a hill and watching the temp on the tranny rise...not a great feeling.

I don't do that anymore lol. And despite a drop in speed climbing the small grade, it does just fine, doesn't get hot or anything and doesn't drop down in gear like that when keeping it in 3 and the cruise off.

I'm guessing the gearing isn't going to matter much for fuel mileage concerns for you...in fact I doubt you would recoup the cost in the switch while doing so. Now if your having issues pulling up a grade and you think it will help, then something to think about.

For mileage just plan on 9-10 mpg when you tow. And just be happy gas prices are down right now! Last year we went all over the place and gas was 3.50 - 4 per gallon. I just hope they hold out for this year a little longer.

[Desert185]

Originally Posted by rnkburg

I did a swap on my cummins and best thing I ever did for the truck. I had 3.55 and went to 4.11. People said I would hate it but it gives me two ranges to choose from. With stock tires I can run 4.11 and with my 35's it drops to 3.73 ish truck runs easier while towing and although no one will believe me it toes better with the 35" tires on vs the stock size. I have towed my raptor 300 with this and truck pulls like a dream. I mainly tow with my dually but the 3/4 pulls the trailer just fine. I did front and rear swap and ordered parts from Randy's ring and pinion. Great guys to deal with and best prices around that I found. He also has a calculator on there as well.


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I've considered the same thing, but having to change both the front and rear gears is holding me back. I can run in 5th now at 60 MPH, if needed in a wind or on a grade for EGT purposes. Having a stick, my tow/haul mode is my brain and right hand.

You have a stick or an auto?

[Jlwright]

I got my terminology wrong. I meant the front ring and pinion gears. I have the 6 speed auto with tow haul mode. I will stay with the 3.42 gears this summer and see how it goes. I really appreciate all the advice. I think running in 5th gear is a good idea.

[bmach]

I would check out if you even need to change gearing. I have a 2013 Ford with 3:55 and it tows my 6000# trailer with no problems.

[BirchyBoy]

Originally Posted by Jlwright

Is reprogramming a dealer only thing or can a good auto repair shop do this?

Take a look for a company called Black Bear Tuning. They can customize the tuning on your truck and possibly help you find a little extra power.

[rnkburg]

I have the automatic. It's kind of a hybrid built tranny with ats converter suncoast dual laminate flex plate. Billet shafts. Suncoast extreme tranny kit. Upgraded valve body. And torque converter lock up control. And running the amsoil race tranny fluid.


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[Desert185]

Originally Posted by rnkburg

I have the automatic. It's kind of a hybrid built tranny with ats converter suncoast dual laminate flex plate. Billet shafts. Suncoast extreme tranny kit. Upgraded valve body. And torque converter lock up control. And running the amsoil race tranny fluid.


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I had a Suncoast in my '94 12-valve. Good tranny.

[rnkburg]

Mine is a 12 valve as well. I love that truck


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[pmedic433]

I went from 3.55 to 4.10 on my 96 f 250 and it made a world of difference! Before it would struggle in overdrive with a 5000# TT, now I pull a 9700 # fifth wheel with ease. I didn't have to recalibrate the speedo because it reads off a sensor ring that is the same in all axles in that model. I guess it is vehicle specific.

[TomHaycraft]

Jlwright, for comparison, here is my experience with a slightly smaller Springdale (only 1 slide, 28' total length).

Same size 5.3L engine, transmission and rear end in my '09, stock 20" wheels, don't know if by 2013 your engine is tuned to turn out any different HP or torque. I'm only 2-wheel drive which shifts weight limits a bit. Last time at the scales, trailer was 7,700 lbs (275 short of the trailer's GVWR), pin accounted for 1,240 lbs (putting me 130 lbs under my rear GAWR), combined weight of 13,380 lbs (89% of the GCWR).

I've been all over Texas, into the Davis Mountains (5,000+ ft above sea level) and into Palo Duro Canyon State Park (10% grade for a bit). I use the tow/haul mode locking our OD, still a lot of hunting between 4th and 5th. Have recently set it to M4 to keep me out of 5th and am able to use the cruise control, toggling it off to allow a bit of speed to bleed off on hills to minimize chance of dropping into 3rd and really spinning up the engine. Much easier driving keeping it in 4th. I try to keep speed at or under 65 mph, engine hums along at about 2,800 rpm. Strong headwinds on the Interstate is tough forcing me to drop the speed a bit as it is more common to drop to 3rd gear. It is at those times I wish I had more engine.

Wife and I are out at least once a month, year round, last year we spent 32 nights in the trailer. I'm happy with the combo, hope I can hold off on upgrading the truck until I have cash on hand, might be another 4 years with the price of 3/4 ton diesels!

Hope this helps! If you want more details, PM me!

[Jlwright]

I really appreciate your input. Obviously I would have bought a different pickup had I known I was going to buy a fifth wheel. With only 4000 miles on my current pickup I am certainly not wanting to trade right now. Most of my travels will be south from Arkansas to the gulf and Texas so we are hoping we can make due with what we have. The truck has no problem pulling the trailer it just needs to stay in lower gears. I used a 1 ton flat bed in my business for years with only a four speed manual. It ran around 2700 to 3000 RPM at 60-70 MPH. It went 200000 miles before being overhauled. I doubt we will put over 3000 miles a year on the pickup and trailer. I will reavaluate after the first season of camping.
I can't wait for warmer weather to try it out. Looking at it sitting in the back yard is killing me.

[TomHaycraft]

When replacing my last truck (after 13 years and 180,000 miles), in 2009 didn't think I'd be at that place in life to purchase the 5th wheel during this truck's life. When looking for trailers, I found the 247FWRLLS had one of the lightest pin weights for its size, has been perfect for wife, dog and I. We are sticklers for paying cash for everything except the house. Could get a loan in a heart-beat for bigger truck, but we'll make-do with what we have, get every mile we can out of this truck in the interim.

Winter in Texas? So long as there isn't ice on the road, we go. We were out weekend before last at Cedar Hill State Park near Dallas. Rain and temps in the low to mid-30s. Not a setup to full-time in during the winter, but for the weekend, we weren't home!

Enjoy your trailer, safe travels.