noob question: transmission upgrades 2007 Yukon XL

[jbro507]

Hi All,

Newcomer here. Bought a used 2003 Forest River Wildwood 31BH in great shape and I'm starting to plan what I need to do in order to properly tow it next summer. I plan to tow it with a 5.3L 2007 Yukon XL. The TT came with a weight dist. hitch and I have a fairly higher end brake controller installed. I also had an aftermarket trans cooler installed in the XL.

Anyone have any experience / comments on installing a shift kit on one of these GM SUVs? My mechanic says it's a good idea and recommended I install a mild sift kit and a "Corvette Servo". In fact, he himself did this same upgrade in his Chevy PU. He took me for a drive and it seems tolerable. He did say something that worried me - (paraphrasing) something about "yeah, when you put it in tow haul mode it's really going to kick you in the ass" but then followed that up with "but with all the weight behind you with your RV, it'll be fine".

Anyway.. any thoughts on this idea? Worth the money? Is it going to start killing other parts down stream (U joints, etc)?

Thanks!

JB

 

[Carl L]

According to trailer life's tow rating tables, that Yukon has a tow rating of about 7000 pounds. Good practice is to limit your trailer gross vehicle weight (GVWR) to no more than 7000 pounds ? 5600 pounds you are going to tow in the 11 Western states. What is the GVWR of that 31 foot trailer? I suspect it's going to be well over those limits.


If that is the key indeed the case, fussing around with transmission ratios and shift timing will gain you little or nothing while you develop problems with driveline strength, brake sufficiency, and suspension problems. Your problem will not be so much with going up the hill as coming down the other side.


So what is your trailer GVWR?

 

[Frizlefrak]

So what is your trailer GVWR?

I'd be curious to know that too....a 31' trailer is a LOT to ask of a 7 year old Yukon....if for no other reason than the wheelbase is short and I'd be concerned about sway above all else.  My 30' grosses at near 8000 lbs.  I tow it with a Ram 2500 Cummins diesel.  I can't imagine trying to pull it with much less, especially out here in the high country. 

The transmission mods he's talking about will alter shift points and make the shifts snappy and rough.  I doubt you'll gain any reliability or durability without going to heavier clutch packs and torque converter. 

My advice?  Leave the transmission as it is and change titles.  Your trailer is likely near mine in weight, and you're getting into that gray area of "3/4 ton" (ie 2500 series) truck needed to pull it safely.  There are some modern "half ton" trucks that can be configured to do the job adequately, but you're nearing the limits of a lot of them.  And the closer you get to your tow vehicle's limitations, the less fun towing is...and it can get downright stressful if the tow vehicle is overburdened.

 

[jbro507]

So what is your trailer GVWR?

Frizlefrak, Carl, thanks for your time.

Luckily I think I got a great deal on the TT so if have to, I can sell it if it's too big for the Yukon and get my money back.

I'm not looking to upgrade the transmission to justify over loading the truck. I totally understand the whole truck is rated for a max towing weight for a reason (brakes, stability, etc). I was only hoping to give the trans some added life knowing that I was going to do some towing near the manufacturer's limit.

A quick look online has the TT at 5,660 assuming this is accurate: http://www.nadaguides.com/RVs/2003/Wildwood-by-Forest-River

I also assume that's dry weight.

I don't know my axle ratio, but the towing capacity of the Yukon is 7000-7500. I bought the trailer thinking that the approx 1 ton difference between a 5,660 trailer and 7,500 towing capacity would be a sufficient spread to cover the weight of the people and our stuff. I knew I was up near the limit. Knowing we were near the limit, we agreed we'd stay in the relative flatness of the mid-west until we upgraded the tow vehicle.

Also, I agree that SWB trucks are not good for towing, which is why I specifically bought the XL. Is the LWB XL no better than a LWB pick up?

So, anyway, looks like my transmission upgrade question has morphed into a "am I overloading my tow rig" question.

Thanks again.

John

 

[jbro507]

There are some modern "half ton" trucks that can be configured to do the job adequately, but you're nearing the limits of a lot of them.  And the closer you get to your tow vehicle's limitations, the less fun towing is...and it can get downright stressful if the tow vehicle is overburdened.

I just re-read this and I think you basically answered my question at the end of your 1st reply...

 

[Frizlefrak]

Furate: http://www.nadaguides.com/RVs/2003/Wildwood-by-Forest-River

I also assume that's dry weight.

John....that is indeed likely dry weight.  My trailer is similar size, and it's dry weight is within a couple hundred lbs.  The problem with dry weight is this....it isn't anywhere near accurate.  Dry weight may not even include the A/C, awning, propane tanks and propane, spare tire, options, or a plethora of other things.  It also doesn't include the weight of the hitch itself.  The trailer was likely 800 lbs over dry weight before anyone put so much as silverware in the drawers.  Gross weight is what you generally want to use when calculating what tow vehicle is appropriate.  Dry + Cargo capacity = Gross weight.  The best way to determine travelling weight is obviously to load the rig up ready to camp and get it to a commercial scale....but in lieu of that, gross weight is used.

Then there is tongue weight.  If the trailer is 7500 lbs and the hitch weighs another hundred, that's close to 850 lbs on the bumper of the Tahoe.  Depending on how the tow vehicle is loaded, you could be nearing it's payload capacity even if you're still within its towing specs.

Even if you're not loaded for a 3 week excursion, I'd be willing to bet a 5500 lbs "dry" weight trailer is well over 7000 lbs before it leaves your driveway.  Again, lots to ask of a Tahoe...even a brand new one. 

I know we got off course from your transmission question, but just a first draft of running the numbers, you're very marginal on weight in a best case scenario, and overloaded anything beyond that.

 

[jbro507]

I know we got off course from your transmission question, but just a first draft of running the numbers, you're very marginal on weight in a best case scenario, and overloaded anything beyond that.

Again, thanks for your time on this. I'll do some digging and decide whats best - sell the TT and go smaller or get a bigger tow rig.

Thanks again!

- John

 

[keymastr]

When I see questions on my boating websites about ways to add horsepower to make a boat faster the overall consensus is that it would be far cheaper to just buy a boat with the performance you want. The answer here is the same. A shift kit will not help your tranny much, it eliminates a few milliseconds of slip between shifts so it MAY save your clutches a little wear but a better option would be to add a fan assisted transmission cooler so that the fluid stays cooler in the first place and can cool those overworked parts.

I would buy a smaller trailer or a bigger truck but here is a link to the cooler. http://www.jegs.com/p/Derale/Derale-Electra-Cool-Remote-Oil-Trans-Cooler/961947/10002/-1?itemPerPage=90&pno=1

The beauty of this type of cooler is that it still cools while in traffic or at stop lights when no air is moving through your normal cooler. Also if you leave your rig running for a couple minutes after a tow it will keep cool fluid going through that hot tranny so your fluid does not sit in the hot spots getting burned.

 

[jbro507]

I would buy a smaller trailer or a bigger truck 

Thanks. 

This is the direction we're leaning right now. Probably smaller trailer.