GMT800 Suburban Towing issues: Gearing or power?

[Martinjmpr]

Closing in on 3 years now of using the 2004 Suburban (1500, LT, 5.3, 4x4, 4L60, 3.73 gears) as our primary tow vehicle. Previously we had a 2,000lb T@B trailer but in January we upgraded to a ~ 3500lb R-Pod 179.

The "issue" I'm having is when climbing steep, high passes (here in CO you can't get from the Front Range cities to the mountains without crossing at least an 11,000' pass.)

As I slow down, of course the 4 speed 4L60 drops into a lower gear. 2nd gear is actually pretty good for climbing and I can typically keep up with traffic at around 50 mph even in 2nd. But as the hill gets higher, the weight bogs the rig down and speed drops. When it drops below about 35, the truck wants to kick the transmission down a 1st gear - which of course makes the engine spin around 4500 rpm (screaming.) That typically only lasts a few seconds before it shifts up to 2nd but then it bogs down again and drops back down to 1st. This sometimes happens 5 - 10 times while ascending a steep pass (think Eisenhower Tunnel or Berthoud Pass, for those familiar with them.)

When we had the T@B this never happened, we could stay in 2nd gear the whole time. But our trailer weight has nearly doubled and I can really feel it when climbing those steep passes.

Not only is it a bit of a shock to feel the truck dropping down into 1st gear, I'm worried about what those hard shifts and high RPMs will do to my transmission and engine (transmission was rebuilt 2 years ago @ 150,000 miles and has worked fine since then.)

So my question for the GMT800 Hive Mind is this: If my goal is to be able to ascend passes more easily, should I be looking at doing something to boost power/torque or should I be looking at lower gearing?

I'm not looking to spend a ton of money and I don't want to put too much stress on an already middle-aged drivetrain (170k) so I don't think turbo/supercharging would be a good idea for me. Are there less "radical" power mods that would boost the power of the engine?

EDITED TO ADD: I'm not a huge fan of things like Cold Air Intakes or air box removal - I'm just skeptical that they really improve power. Ditto for "reprogramming" the computer, as I think that assumes that the "tuners" know more about the engine than, you know, the people who BUILT it. Adding power and sacrificing reliability or utility would pretty much defeat the purpose of what I'm trying to do here.

Or would it be a better idea to simply change the gearing to, say, 4.11? And if I was to do this, what would I be looking at, cost-wise, to replace the front and rear gear sets (and ideally retaining the G80 locker in the rear?)

Anyone else had this issue with a 1500 'Burb towing? (If I'd known we were going to be getting a heavy trailer like this I might have held out for a 2500 but that's 20/20 hindsight at this point.)

Thanks in advance!

 

[DailyExpedition]

So I just left Colorado this past week, went on a trip starting from Durango and zig zagged up towards Denver then back out through the Springs. I feel your pain I drive a 1998 GMC Yukon and going up the passes were hell. Of course I’m running tires that are much bigger than stock and I have 3.73’s. Even though I wasn’t towing anything it was a struggle. I’ve been researching what to do to fix the issues. First thought was gearing, then an exhaust upgrade, then a tune. I’m like you, I’m old school I’d rather ad something physical to make power as opposed to a tune. However in your rig you have an LS engine, their performance can be greatly increased with JUST a tune. Of course you could add 30-40 hp with doing headers, high flow cats and high performance muffler. A tune will only run you about $500-$600, full exhaust about $1500, gears $800-$1000 if you can do it yourself. So really a tune could be just what you need. Black Bear Performance is pretty much the leader in tuning for GM trucks and SUV’s. I’ll be doing all three, just don’t know what order yet


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[XJLI]

Headers, cats, exhaust and tune is worth 30-40 to the wheels. You don’t need more gear if you are running the stock tires or only one size up... your burb has 3.73s already. You have the Corvette shift servo? It should hold 2nd longer than the stock one.

 

[NMC_EXP]

We have a '99 K1500, 5.7L Vortec. Don't know the diff gearing but based on the way it rolls downhill it is high. Differnet engine and all but for what its worth, it acts the same as yours when towing a 3000 lb RV. Right down to the 1st gear downshift and 4000 RPM.

Last year the engine let go during a 4000 RPM episode on one of those big hills on I25 near Walsenburg CO.

I cured my towing problem with a 93 Dodge W250 5.9L Cummins and 4.10 gears.

 

[NoDak]

The only real solution that is easiest on the drivetrain and wont affect reliability like some other mods is lower gearing. 4.10 or 4.11 would do nicely.

 

[Ducky's Dad]

EDITED TO ADD: I'm not a huge fan of things like Cold Air Intakes or air box removal - I'm just skeptical that they really improve power. Ditto for "reprogramming" the computer, as I think that assumes that the "tuners" know more about the engine than, you know, the people who BUILT it. Adding power and sacrificing reliability or utility would pretty much defeat the purpose of what I'm trying to do here.

I don't tow, but I do spend a fair amount of drive time in the mountains, up to about 8000 feet. My Dodge 5.7 gasser was a little sluggish at altitude and going uphill, even with a CAI and big exhaust, mostly because it is almost always loaded with stuff. I finally broke down and put a programmer on it (Edge), and it made a huge difference in performance, even on the 87 octane tune.

 

[ExplorerTom]

Gears. I know a guy that will do them for $850. Front and rear. Installed. You may want to budget for new bearings (probably an additional $150 for each axle).

I've been thinking about 4.10 gears for my Expedition. And I don't tow.

I can't comment on whether or not you can keep your G80 or not.

Let me know.

 

[rayra]

Does your vehicle have the towing option package, do you have the Tow/Haul mode and if so do you use it?
What octane of fuel do you use, have you tried higher octane on these uphill trips?
Problem is keeping your vehicle in the power band of the motor. More engine HP, or taller gearing.
More importantly, IIRC, you bought your vehicle somewhere south and flat (IIRC), have you ever had the battery disconnected / engine comp disconnected, had the vehicle 're-learn' your higher-altitude driving routine? It will make some (limited) accommodation for your higher altitude driving routine.
I believe there is a programming option to change and soften your shiftpoints. And If I'm not mistaken computer hardware available to swap that firmware on the fly, as needed.
Lastly, you know the hard shift and screaming RPMs are coming, so just hit the hazard lights and ease off and make the gear change manually when more appropriate. Exert some manual control on what's going to happen anyway. Don't kill your motor or trans trying to maintain a higher speed. Pull over and let backed-up traffic pass you when you reach your state's limit (in CA I think it is 5 vehicles stacked behind you)

IMAO it's these high load high RPM steep grade climbs that kill the 4L60. Trans temp is the key concern. Amend or improve that if you haven't already. I'm getting crazy low trans temps with my cooler install (verified with a laser thermometer, I have got the right data selected for my Torque app trans temp gauge). But I'm rarely topping 4-5k', not your 11k. 11k's rough on any vehicle not tuned for it, even computer-controlled and fuel injected. Even without towing a load.

 

[plumber mike]

The only real solution that is easiest on the drivetrain and wont affect reliability like some other mods is lower gearing. 4.10 or 4.11 would do nicely.

Agreed. I’d look to smaller tires as a cheaper easier solution to try before I made the investment in gears on a rig that age

 

[ajmaudio]

I know you mentioned u dont like the idea of a tune or intake, but having been through exactly your predicament they work. Not an air box replacent.. but replacing the factory intake tube with its rough accordian shape and giant resonator/silencer makes a surprising difference. A 3" exhaust, and tune with the intake tube made a real difference. Tuning the trans also has major benefits.

 

[Buliwyf]

Rpm is harmless, I'd worry more about hard shifts. Let the engine sing, and manually downshift it early. Don't wait for Gm's miserable cruise control to do it for you. That engine isn't even remotely close to being able to hit ''high rpm's'', so don't worry about it.

First gear sounds excessive for that grade and trailer, might be worthwhile to get that truck on a dyno to check your AFR's. I know you're not interested in tuning, but dyno testing is a major diagnostic tool. I'd expect better power from that truck.

3.73 to 4.10 is hardly noticable. Try 4.30 or 4.56. Expect a $2000+ bill, so get plenty of gear done right. Make sure to use full throttle every once in a while so the ecm can read ambient air pressure and temp and adjust accordingly.

I thought the 5.3 could handle a little 3000# trailer??? Tried to warn ya'll about 1500 'burbs, and ya'll went ape. Remember? Gear swap costs as much as the premium cost of used 2500's over 1500's.

 

[ExplorerTom]

. Expect a $2000+ bill, .

You can tell who reads everyone else's response first before replying, and who does not. Like I said, I know a guy who makes his living regearing Jeeps and trucks out of his house. Local to Martin and I. $850 installed. Front and rear. He did my Explorer.

 

[ClovisMan]

You can tell who reads everyone else's response first before replying, and who does not. Like I said, I know a guy who makes his living regearing Jeeps and trucks out of his house. Local to Martin and I. $850 installed. Front and rear. He did my Explorer.

Your Explorer has stick axles. They are much cheaper to re-gear than the Chevy Front IFS contraptions the GMT800 has.

 

[Buliwyf]

I read it, just ignored it. That's FREE. What's the catch?

Does he have acreage? Because if he can swap gears for anywhere near that consistently, half of this forum will be camping out in his yard.

 

[ExplorerTom]

I read it, just ignored it. That's FREE. What's the catch?

Does he have acreage? Because if he can swap gears for anywhere near that consistently, half of this forum will be camping out in his yard.

He does have acreage. About 5.

What's the catch? He doesn't have the overhead that a shop does. It's just him.

https://denver.craigslist.org/pts/d/07-17-jeep-wrangler-jkre-gears/6669647048.html
I can't find his same listing for F-150/F-250/F-350/Excursion and other full size vehicles, so his prices might be a little different for the larger vehicles. Check his Facebook page for pictures of most of his customer's vehicles. He's a Ford/Jeep guy but will also work on Chevy/Dodges. He won't work on Toyotas.