New tow rig aquired. 4L60 advice needed so I'm not setting myself to be stranded.

Hey Guys and Gals, I've been looking for a new tow vehicle for a while now so when I finally found a lower mileage truck that wasn't crazy overpriced I bought it 30 minutes after it was posted to Craigslist. It's a 2007 GMT900 Silverado 2WD extended cab with the 5.3 and tow package, with 127k miles on it. It's price was just too good to pass up, and it's left me with some pocket change to get this truck setup for towing. My biggest reservation is the 4L60E behind the 5.3. In the past, I've not had much luck with automatic transmissions, some of what I'm reading is just get a giant trans cooler, and watch the temps and I'll be fine. Sounds great but I dunno,  I guess what I need to know is if the 4L60E really up to towing my 2k lbs wood floor trailer with, say a 3K lbs car, on it in the long run, or will I be replacing these things every 30k miles. My closest tracks are NCM and Road ATL, so there are plenty of hills to two over on those trips from Nashville.

I'v been looking around and it looks like there's the possibility of replacing it with a 6l80E from the SUV line. So has anyone around here done this swap, 4L60E to 6L80E?

Since no thread is complete without pictures, here it is. It needs a new bed or bedside on the passenger side and fender arch on the other side from rust, passenger mirror, driversdie front bumper corner cover, tires, TPMS sensors, and some good all weather floor mats. But for less than 5k I couldn't pass it up. I'll start a build thread for it, just to document the fun. Also thinking of lowering it since it's taller than my 4wd OBS '94 and I'm sure that can't be great for fuel mileage.

I have a 99 Burb with the 4l60e in it. I just make sure to tow in 3 and it's been nice so far! Sorry,I don't have much in the way technically to add in.

Nice looking truck!

Looks like quite a score.   Get the biggest trans cooler you can fit into the truck and you should be fine for those hauls.  How often do you plan to use it to haul your racecar?

Believe that the factory says the 5.3 in an extended cab is good for ~6800. It won't be terribly fast towing 5000lbs but will make it just fine.   I've towed a uhaul/car hauler in my GMT800 tahoe with no issues.   

In reply to t25torx : How you drive a truck tends to make a big difference in how the transmission holds up.  

That and change the trans fluid every 65,000 miles. Don’t assume it’s ever been done, have it done very soon!  It may not have been done.  

I’ve pulled big heavy tandem axle enclosed trailers all over the country with relatively  small vehiclesMercury  passenger car, ( S10 Blazer )  1/2 ton pickup    Never had a problem with a transmission.  Hundreds of thousands of miles all over the country.  Mountains deserts tow at the high speeds out west and rush hour traffic.   I’ve never used aftermarket transmission coolers because the fluid needs to quickly warm up on cold mornings and most aftermarket coolers aren’t tied into the radiator so they can’t warm up quickly.  

If I know the fluid got too warm it’s changed right away.  Not just flushed, changed including the filter! 

I ease the vehicle into the load, don’t slam it and jerk it around. Learn to sense when the transmission is shifting and momentarily feather the throttle so you aren’t causing the clutches to slip excessively. 

If it has  a tow package it may have a trans cooler already.   While checking for a cooler, scope out the transmission lines.  Gm had a funky way of routing them on some models which made them prone to rust.  Causes a leak and bang, don't  see it coming.  Ask me how I know.   Do a tranny service regardless.   Do you know if the PO hauled much?  

I had the same transmission in a Buick Rainier, and it towed ok, smaller loads than you, but ok in 3rd.  That was in the hills and dales upstate NY.  Good luck with your new ride.

Tractor fluid.

Ranger50 said:

Tractor fluid.

What is tractor fluid? Heavy duty trans stuff?

Jaynen said:

Ranger50 said:

Tractor fluid.

What is tractor fluid? Heavy duty trans stuff?

John Deere HyGard for wet clutches or a similiar product. Replace 4 qts ATF with it. I have the cheapest stuff from Tractor Supply ready to go when I do my vehicles here soon.

t25torx said:

I'v been looking around and it looks like there's the possibility of replacing it with a 6l80E from the SUV line. So has anyone around here done this swap, 4L60E to 6L80E?

 I have two vehicles with 6L's in them... Not worth it. I'm already fighting an increasingly annoying and occuring flare shift from 3rd to 4th. When it dies, I'm backdating to a 4L80.

Ranger50, you say Tractor Fluid, then complain that your transmission is about to die.

Did this transmission have tractor fluid in it?

I ask because I just got off my John Deere (doing the landscaping for a local business) and deal with fluids for tractors, they have different additives and I would caution about running them in an auto transmission.

Its like diesel antifreeze, there is an additive for the electrolysis that happens in a diesel engine but that does not (or to a much lesser degree, like a magnitude) in a gasoline engine. It keeps the antifreeze from eating the gaskets in the engine.

In reply to Bent-Valve :

No, still factory dex vi.

As for running tractor fluid in an auto trans, people have done it for yrs. Type F is red tractor fluid for the most part. Ford just added some of their own additives that don’t like heat and varnish up valve bodies which tractor fluid does not.

Want you’re mind blown? I’ve seen 5w30 motor oil run on top of 20w air compressor oil... doesn’t seem to matter.

I had a transmission guy tell me to NEVER tow in overdrive with these transmissions.  Add a temp gauge and keep an eye on it when towing. I've towed a lot for the past ten years with 3 different Burbs/Yukons and had no problems.  Be gentle and keep it cool and you should be OK.

Cooler is always a good idea! 

Remember that transmission work based on the rules of physics, not internet rumors. If your transmission is NOT slipping while towing, then it's also not wearing appreciably faster or making much more heat. So steady state towing does not hurt the trans.

What towing does do is cause you to shift more frequently.  Shifts, especially under heavy engine torque, do cause wear.  I say engine torque and not 'load' or weight because the transmission just cares about a torque difference between the input and output. Since you run the throttle regardless of how much weight you've hooked up, it is always YOU that's in control of whether the trans is experiencing a big torque delta. The way i've always driven around this is downshifting with the shifter under light throttle, and letting off throttle for upshifts and then 'rolling back on'. Eventually this advice will be obsolete as modern vehicles have already been modulating engine torque during shifts for 20+ years and it's become ubiquitous across all types of vehicles in new cars. Don't think your 2007 does much of it, though..

But in general, if you can tow in 4th gear without the trans frequently downshifting or coming in and out of torque converter clutch lockup, you're not hurting it. If it starts shifting on its own, just take over and do it yourself so you can control the 'torque delta' during shifts. Anything past that would just be a 'normal' failure if anything goes wrong. 

Vigo said:

Remember that transmission work based on the rules of physics, not internet rumors. If your transmission is NOT slipping while towing, then it's also not wearing appreciably faster or making much more heat. So steady state towing does not hurt the trans.

Transmissions are a long way from being 100% efficient.  If you assume that 10% of the power you put through it is lost as heat (which is an overly simplistic assumption, but it'll do for discussion arguments), then the more power you use, the more heat goes into it.  Towing a trailer requires more power, thus more heat in the transmission compared to driving the same vehicle unloaded.

Most of the heat a trans generates is in the converter slippage (which doesnt occur when it locks) and in the pump (which varies with rpm but not load unless it's got a PWM regulator solenoid that the computer is controlling in reaction to engine load).   The clutches don't create heat unless they're slipping and the various bushings and thrust bearings don't create much heat either.  Only some of what makes heat in a trans is actually 'load dependent' but those also happen to be the things the driver can control if they are aware of it and choose to. 

This is also why scaling drivetrain losses up the way people do to extrapolate ridiculous CHP numbers from chassis dynos is pretty much bullE36 M3, but that's another story.

4L60e has a VERY bad reputation for losing 3rd gear.

Depending on what package you have there may or may not be a transmission temp readout on the display that you can toggle to. On my 2007 with the tow package I have that. I watch it obsessively with 200k miles on my truck. It towed the airstream back from Michigan fine last summer though things did start to get warm in Minneapolis stop and go traffic with air temp's over 95. If you can watch the temp you can alter you driving/turn the AC off to keep things reasonable. For what it's worth, right about when the trans started getting warm the coolant temp gauge started to move. My bet is that the whole built together radiator/trans cooler reach heat saturation at about the same point. 
Put it in tow/haul, don't let it slam gears, and don't be afraid to slow down a bit to keep it in it's happy place. 

imgon said:

I had a transmission guy tell me to NEVER tow in overdrive with these transmissions.  Add a temp gauge and keep an eye on it when towing. I've towed a lot for the past ten years with 3 different Burbs/Yukons and had no problems.  Be gentle and keep it cool and you should be OK.

I’ve heard the never tow in overdrive too. Yet my last pickup went 371,000 miles with nothing more than regular fluid changes every 65,000 miles.  Before that I towed with a S10 Blazer. Before that an El Camino. Always in overdrive, never had to rebuild a single transmission. 

Im trying to recall all the times I crossed the Rockies heavily loaded  and it’s probably well over 3 dozen. Round trip! Actually I usually cross both the Rockies and Sierra Nevada’s.  

Some years I also did the Appalachians as well, both ways.  Plus as you know Elkhart Lake is in the Kettle Moraine region which has a few steep climbs invoked as well. ( nothing like the mountains though) 

Always in overdrive.  You just need to be sensitive. smooth and steady, ease into the load and don’t overheat the transmission. 

It’s about 7 hours to Elkhart Lake but I suspect if you don’t care about the transmission you could make it in 6:45 min.  But you’ll spend an extra $25.00 in fuel plus the cost of a transmission rebuild.  

codrus said:

Vigo said:

Remember that transmission work based on the rules of physics, not internet rumors. If your transmission is NOT slipping while towing, then it's also not wearing appreciably faster or making much more heat. So steady state towing does not hurt the trans.

Transmissions are a long way from being 100% efficient.  If you assume that 10% of the power you put through it is lost as heat (which is an overly simplistic assumption, but it'll do for discussion arguments), then the more power you use, the more heat goes into it.  Towing a trailer requires more power, thus more heat in the transmission compared to driving the same vehicle unloaded.

Well explained! 

Full-throttle downshifts are your best friend...if you want to lunch the tranny as quickly and expeditiously as possible.

I like synthetic fluid, and lock out OD in hilly areas.  

And the biggest cooler you can find/fit/afford.

IIRC the 700R4 and 4l60E are very similar mechanically.  Shift kits exist- if the trans isn't in bad shape now, it might be worth a few bucks to put in a shift kit to firm it up.  When we got my wife's 91 'Burb (with 170k on the orignal 700R4) I paid $400 to have a shift kit installed and fresh synthetic fluid.  30,000 miles later and it's still behaving itself *knock on wood* despite some heavy tows.  And still hits the gears nice and crisply when you romp it.  

AwesomeAuto said:

4L60e has a VERY bad reputation for losing 3rd gear.

and WOT 1-2 or WOT 2-3 shifts

4L60e has a VERY bad reputation for losing 3rd gear.

Well, that clutch pack is also used in 4th gear. Kinda funny, eh? 

I recently farmed out (don't have proper bench or press for building myself currently ) the rebuild of a ~340k mile 4l60 that was original on a 2000 Chevy pickup. I've personally never seen one that made it that far before, but lots of them make it to 200k and beyond. The one in our S10 is original at 250k but needs help.  

They do have some weaknesses but well-kept ones still live long lives more often than not. 

The idea that transmissions convert a significant percentage of input power to heat falls apart if you do some math. Let's say you're flooring it in a stock 5.3 up a mountain pass, putting ~250hp through it, or ~190,000w since that's easier to talk about heat with. You convert 10% of that to heat, you now have 19,000w of heating inside your 150lb transmission (a 150lb human would die VERY quickly).  Convert that to heating a house terms and you're talking 64,000 Btu/hr. You think a 5/16" fluid line going to a cooler maybe 10" long that's cooling INTO a ~200f coolant with maybe a ~50 degree temp delta can shed 19,000w of heat gain continually? It couldn't, but it also doesn't have to because the transmission is not converting that much energy into heat.

Transmissions do convert some energy to heat, but it's not a huge amount, and it's not particularly load-dependent as long as the converter is locked. Considering that under normal circumstances there is almost NO temp delta between the ATF and the coolant, the cooler might as well not be there at cruise. And if you are towing with the converter locked up at normal rpm, that IS cruise!  It's only when the converter is frequently unlocked (as it is during shifts) and shifts are occurring bringing you to a higher rpm where more fluid is pumped/sheared that your fluid temp may begin to outpace the capacity of your tiny stock cooler, and you then as an informed driver just 'drive around it'. Or put on a big external cooler and there's a really good chance you don't need to worry about heat at all. 

I've owned my 99 Z71 ext cab 4x4 GMC with a 4.8 for over 12 years now. Purchased with 140K, the trans was rebuilt at 180K and now its at 293K without issues. I have a big trans cooler, use synthetic trans fluid, and change every spring. I put a half bottle of lucas in at each change. I tow an 18 foot car hauler, mostly with 78 Z28 on it and a few times a 79 GMC shortbox. And several other cars and trucks. The tow haul mode is great. I tow in 3 unless flat interstate travel.

Cold air intake, exhaust, and programmer to me was worth every penny for towing. I have a spectre cold air kit, dynomax single catback, and a Hypertech Programmer on premium fuel. The programmer made a big difference on the low end (torque).

The truck owner prior to me, towed a 66 Nova and an enclosed trailer with it.

I'm in Oak Ridge/Knoxville. It won't set the world speed record going up and down hills but it gets the job done.

I bought my ‘96 1500 Ext Cab Silverado (350 w/4L60E) in ‘99 with 100k on it.  I used it to tow my 1,500lb trailer, 2200lb Spec Miata, and 500lbs of support equipment to just about one race a month.  When I sold it all off to get my Camaro, it was 20 years old, and had over 260k on it, all on the original drivetrain.  It had a tow package, which came with the trans cooler already installed.  Most of the time, especially when the temps were in the high 90’s, I’d tow in 3rd.  If it was in the 60’s, and I could maintain a good steady pace, I’d use o/d for slightly better mileage.

And it is a 700R4, just with electronic control.

Thanks for the input guys. I will do a flush and fill with synthetic and looking at some other forums I might try the JD HyGuard stuff mixed in. Guess it wouldn't hurt to drop the pan and put a new filter in it. I have a 12"x12" B&M Oil cooler that my brother was going to use on his V8 S10 about 15 years ago and never did, think there would be any issues using that as a trans cooler?