Towing with a 4l60e, best practices.

You may remember that I posted up last fall that I killed the transmission in my 96 chevy conversion van towing my race car to an event. I bought the van used last spring, and it had towed a bunch in its life previously. 115k miles. I use an open trailer and my race car is 2800 pounds on the trailer.

I got it rebuilt, had them add the biggest tranny cooler they could. However, like anything I own if I break a part I don't really understand.....I then become paranoid for life. I picked it up last night and it works just fine. A friend rebuilt it, and he's good at what he does. He told me I could hammer on it with little problem now.....but that's not my nature. Just want to ask the collective a few questions. I don't expect I'll have this thing for another 100k miles, but I still want the tranny to last in good shape. Is there any sort of break in I should do before towing with this thing? There is no tow/haul feature on this van and other gm trucks I've seen have that. Am I right to think it just keeps the tranny from shifting into forth gear? Should I avoid 4th gear? Over thinking it?

I do have the obd2 torque app on my phone that I just got recently, and the truck is obd2, I've not connected it up to see if it can read transmission temp or not. It will read rpm, and the truck doesn't have an oem tach.

Probably just being paranoid. Probably tow 20 hours or less over a year, 1500 miles max. The van doesn't see much use otherwise.

sachilles wrote: Just want to ask the collective a few questions. I don't expect I'll have this thing for another 100k miles, but I still want the tranny to last in good shape.

You should see an easy 50k service life, provided you don't do one thing to it.

sachilles wrote: Is there any sort of break in I should do before towing with this thing?

Nope, just drive it. Once the clutches are soaked with ATF, it's ready to go.

sachilles wrote: There is no tow/haul feature on this van and other gm trucks I've seen have that. Am I right to think it just keeps the tranny from shifting into forth gear? Should I avoid 4th gear? Over thinking it?

I always avoid OD in the 60/700's. It was never really designed to have tow loads applied to it. No, tow/haul mode changes the calibration in the PCM. It holds gears longer and ups the line pressure to ensure proper apply and hold. Tow/haul mode showed up in 98 or 99, IIRC.

+1 on never towing in overdrive with a car-based automatic. (The 4L60E is an electronic 700-R4 which was a TH350 with an overdrive stuck on it so 140hp Caprices could get better fuel economy without 2.29 gears)

I think, but aren't certain, that tow/haul also prevents the torque converter clutch from locking up. That's another item that's not really meant to see significant load.

The giant cooler is the key, get a trans temp gauge if you're paranoid.

big cooler + no OD with load

that has kept me out of trouble. i smoked a 700r4 towing a 2000# trailer on a slight incline for a long while, because i figured i could drop it into OD. it got so hot it puked out the vent. once it cooled off it was fine, however whenever it hit 3rd gear it would puke fluid out the vent, so it was an unpleasant ride 200 miles home. i had to do 1-2, manually hold 2, then drop into OD to prevent fluid puke. not cool when it had to go to into 3rd to go up a hill with a highway patrol officer on my tail.

I had a 97 GMC Conversion Van I smoked a few 4L60's in towing open a few hundred pounds heavier than you. When I put the 3rd trans in I added a temp gauge. I had a huge cooler up front and had it routed trans-temp gauge-cooler-radiator(need to put heat in for MN winters)-trans.

Biggest issue I found was I needed to slow down. I would tow at 80 and it wouldn't take much to bring it up to 210-225. Slowing down to 70 would keep it 165-185. I also had been using OD and that would be good for 25-30* just dropping it into 3rd.

Hope it helps.

I agree with all of the above. If it was being rebuilt though I would have upgraded and bullet proofed it while I was in there.

Actually I would like to add one thing: Substitute 2 or 3 qts of ATF with Tractor Hydraulic Fluid for Wet Clutches.

I'll find out exactly what he put inside, fairly certain he put in a upgraded sunshell based on suggestions either made here or another forum. I forgot what else, but we came up with a list. It's greek to me. I didn't talk to him much on pick up as we were both in a rush to get places. I'll talk to him in detail on monday.

So much bad information in this thread...

You can tow with a 4L60E in OD just fine. DON'T TOW IN OD WITH THE TORQUE CONVERTER UNLOCKED.

Pretty simple. If you got a decent/correct rebuild, combined with your huge cooler, it'll last forever. I've saw factory 4L60E's go over 500,000kms with over 100,000kms of that towing in OD.

I've towed 7,000 pounds in my 93 GMC 20,000kms so far through the mountains (basically constant mountain towing) without issue on the new rebuild. It was built for towing, but nothing exotic. We're talking directly through the rockies. I do take a couple precautions though, I prefer to drop it down to 3rd before I reach hills I know it'll kick out on. If it unlocks the torque converter for more than about 10-15s in OD, I'll also manually kick it down. If I hit something where 2nd is necessary, I make sure to not let it kick down under heavy throttle.

I'll report back after another 20k of towing this race season.

Find someone who can flash (or burn a chip for) your PCM. They can program it to increase shift firmness. From the factory, the shift points are designed to give you smooth, gentle transitions between the gears so old ladies don't complain. That is when 90% of wear happens - just like with a manual transmission. There is no wear when the clutch is disengaged or fully engaged. Its that slipping while they are engaging that causes the wear. The less time your 4L60E spends engaging and disengaging clutches is always a good thing. I had my Ford programmed to keep the converter locked in all conditions above 35mph. That way it never unlocks the TC on the highway which really helps keep heat down. I'm not sure you can do that with GMs but its worth looking into.

GM also used clutches and steels from the lowest bidder. They're about as effective as toilet paper. As they wear they can start slipping even when fully engaged. That is where massive heat starts building. From there its all downhill. The fluid can't lubricate as well, temperatures spike, and the additives in the fluid burn. Then you no longer have tranny fluid, you have toxic abrasive sludge.

Your PCM already defaults to full pressure at WOT, so you can't really do much there without valve body mods, but bumping pressure for part throttle can do a lot for longevity.

Change fluid and filter every 30-50k. Its really easy. Drop the pan, change the filter, replace pan, refill with about 5-6 qts. If the fluid is brown, change it more often. When you call for a filter they'll ask you if you have the deep pan or the shallow pan. You have the deep pan.

Your OBD2 should tell you trans temps. There is a transmission temp sensor that is buried in the internal wiring harness of the transmission.

I have the app called torque on my phone and a blue tooth adapter. Haven't had chance to hook to my van to see what info it can pick up. The gm codes that it suggests it can get as well as generic stuff is RPM(no tach in the dash), gear indicator, transmission temp(a few methods, unsure on difference) and TCC slippage speed(rpm). No idea what the slippage speed actually tells me. I assume if locked the slippage rpm should match the engine rpm?

More research suggest that the slip rpm should be 0 if the torque convertor locks up. Should not exceed 150 rpm when slipping. Excess of 150 will set a code.

You know how they say hind sight is 20/20? The more I read, the more I realize there were warning signs from day one.

Curtis nailed it, the soft shift tuning is what kills them under a load. I upped the shift pressures on an ax4n (which almost always fail at 120k) and beat the hell out of that trans.....sold the car at 129k, it now has 277k on it with its current owners without issue. I towed another taurus on a dolly with it for awhile as well.(figure 4k lbs rolling)

OD shouldn't be your issue, just make sure for steep inclines you lock it into 3rd. My guess is that yours was just tired already from a lifetime of smooth shifts.

Another 'smooth shifts kill 'em' vote here. Smooth shift = slip during shift = heat buildup = fried 4L60. There are torque converters out there with HD lockup made just for towing, and a big cooler is a must in any towing application. It also is not good to tow upill in O/D, i.e. it needs to downshift pretty quick. If it doesn't do it on its own, as others have said do it manually.

My Trooper drops into TCC lockup at ~45 MPH and stays there pretty much all the time after that. I leave it in O/D when towing, it drops quickly into 3rd on inclines.

I keep my 4L60 in 3rd when towing simply because I had a thrust bearing fail in one from towing in OD. I forget exactly which one it was, but I remember clearly that it was something that wouldn't have failed in 3rd.

In addition to a bunch of good advice above, I would reiterate two things:

• Don't tow in OD with an early 4L60E
• An aftermarket transmission cooler is a wise addition

HiTempguy has all the correct answers & hints for making this trans live....

Also the 700r4 and 4L60e both block off the trans cooler when in OD...NEVER unlock the torque converter in OD when towing...Fluid temps skyrocket...To be honest, I try never to unlock the converter even when not towing...I'll manually pull it down to D.

On the 4L60e the "Tow/Haul" button ups pressures, shift points & keeps the converter locked up at greater throttle angles.

Tried to get the torque app to connect up with the computer the the GM Pid's and I couldn't get it to work other than the generic obd2 stuff(at least for now). So it really only gives me a tach. I may see if I can rig up a torque converter indicator lamp. 3rd gear tow, check.

Strikes me as real odd that it would bypass the cooler in OD.

I love this place.

Planning a pretty long tow experience with my 1995 Silverado. 4l60e. Unknown history on the trans, but the fluid is good. 

Pulling 1st gen neons in a tow dolley.

Am i cirrect is leaving it in third at 60-70 mph, and keep an eye on it? 

No aftermarket trans cooler, however its a factory tow package truck. But the only cooler is the one in the radiator. 

Yup.  Third gear and try to keep your right foot movements slow and steady.  Quick ups and downs with the accelerator will tell the computer to unlock the TC.  Not the end of the world if it does, just a little tip to help keep temps down, but I don't think you'll have any trouble at all.

I put about 60k mostly trouble free miles on my 01 Yukon with 4l60e. I would leave in 3rd unless I was in the flat sections of the Midwest and over 75mph.

Sold that truck in November and already miss it. 

Make sure it has plenty of cooling.  You can tow in OD if you're on flat ground with a light load, but if the trans can't hold 4th gear with the converter locked (such as on hills, etc.) you need to manually drop to 3rd to make sure it's not trying to run with the converter unlocked (especially in 4th with it unlocked) as that'll make a lot of heat really fast.  

I never had any problems with mine, towing 6000 lbs of travel trailer for ten years.  My advice is lift to shift, 3/4 throttle in each gear, anticipate a shift, lift to 1/2 throttle, let it shift then back in the gas.

Mine had a corvette/z28 servo and a cooler, sold it with 196k going strong.

I think the simplest advice would be to just keep it in 3rd for towing. Adding a larger cooler wouldn't hurt, either.