4L60 acting up

So this year during my annual family vacation I took the '99 suburban on a thousand mile road trip to Massachusetts. New tires, fresh oil change, brakes perfect.....all seemed good.

Of course something had to act up, Murphys Law and all that, right? Well within 20 minutes of our destination it did this weird thing when I tried to accelerate quickly onto the highway. The trans (in I believe 2nd gear) stopped pulling and the revs went to about 3,500. I let my foot off the throttle and it settled shifting up to third and I simply accelerated more slowly to highway speed. Couple of days later I tried it again: same weird activity.

ATF fluid showed a good level but I called a friend of mine who is a very good import mechanic and he suggested throwing a bottle of Lucas into it and crossing my fingers for the 1,000 mile return journey. We've babied it home and (knock wood) are less than an hour out so fingers remain crossed. The ATF is now overfilled a bit due to the Lucas and when checked is bubbly. Truck is happiest at 75+ mph, at lower speeds the transmission has to hunt more and it's feeling uncertain and jerky when asked to do that.

Rig has 232,000 miles on it now and PO told me the transmission had been rebuilt but I have no idea when or what that entailed.

So what do I do now? Dropping the pan and replacing the filter apparently only gets 1/3 of the fluid. Do I do that and then take it in for a transmission flush? Point me in the right direction O' wise and wonderful hive.

I'd do a fluid and filter change if it was mine. You also might throw a transmission cooler on it.

The E4OD in my truck is a little flaky, but a fluid/filter swap and a transmission cooler made a world of difference.

And we're home.

Trans really got unhappy during the last hour. Downshift to climb a hill at 70 and it would stick in third (getting jerky and unsmooth until taking off all throttle inputs , cruise or foot) before up shifting again.

That sounds like it's building heat faster than it can get rid of it. Fluid, filter and cooler might make it last a little longer.

Foreign material in the valve body perhaps? Wonder what the pan magnet and filter are holding.

+many for another dump and fill with new filter and Lucas. Fluid is likely tired/thin anyway and now overfilled, hence the aeration.

All the above just dont have someone flush it or your only shooting your own foot off. Drop pan change filter replace lost fluid add cooler and pray. 4l60s arent known to be very strong anyways, kinda like why they have the moniker "4lE36 M3ty"

Dropped pan. Magnet about 1/4" thick with ultra fine metal paste. I see no chunks or grit but fluid is pretty burned looking and smelling.

Just my guess but I figure it's time for another rebuild albeit only soft parts. Seems in my experience that you will get about 150k out of a factory fresh build, if it lasts that long, or about 60-80k out of a shop build after it's been destroyed. 4l60's have a nasty habit of "welding" the input drum up causing all sorts of various issues especially when OD goes/starts going.

My best advise on this is to run a 50/50 blend of atf to wet clutch tractor fluid. FYI, B&M Trick shift is red tinted tractor fluid.....

New filter in place. Fresh fluid (weird that only like half of it can get changed).

Out for a test drive and it felt a bit "smoother" but when I went full throttle in 1st (from 5 mph) to test things it revved to just over 3,000 and didn't pull hard at all. Then had to let off to up shift. Same behavior in 2nd.

Things seem to work well enough below 1/2 throttle but any more and she's not a happy girl.

Edit for stupid: While I had checked and filled the transmission to what I thought had been the appropriate level, when I checked it after the 10 mile test drive it was just over a quart low. Filled and rechecked and it is now correctly filled. We'll see if it improves.

For now I don't have any big trips planned and if I can avoid towing the club trailer for the rest of autocross season I'll be several months before I need it to do more than local driving (every other weekend when I have my kids and there are six of us).

These commonly have valve body issues. I was having problems with the one in my 98 safari not locking up the torque converter, which lead to very harsh shifts and a transmission warning light. A re-built valve body fixed it and it's been working fine for a year since the repair (knock on wood).

More in the Safari's thread here: https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/lets-go-on-safari-1998-gmc-safari/86217/page1/

So yesterday at the advice of a local and well respected mechanic I took the truck to a nearby transmission shop for a "free diagnosis". The pressure sale pitch started almost immediately. Wanting me to commit to having them do whatever it took to make the truck right.

They call this morning and give me a spiel about the engine having 2,500 misses an hour and that's causing the trans to feel weird.

Can they do a compression test to see if there is a dead cylinder, it's $79 that they will apply to any repairs they need to do.

Sure, go ahead.

Call back a couple hours later to tell me that the cylinder pressures are fine, not great but it's a quarter million mile Chevy so I don't expect great. But they want to do a FULL tune up before they will be able to diagnose the transmission any further.

Hmm, I think I can take care of a tune up myself but just out of curiosity how much?

He hems and haws for a bit then comes out with "plugs, wires, cap, rotor, fuel filter, and clean the throttle body: $540 plus tax."

berkeley you dude. Out of your berkeleying mind, especially since I've done ALL of those things within the last 15,000 miles.

Stupid me for taking it to a shop, bunch of scamming scumbags.

You'd notice a miss like that, sounds like it's slipping, the burnt fluid aids in that diagnosis. Rebuild time.

If you don't have an illuminated check engine like then I think the 2500 misses story is nonsense. I'm voting Kenny's suggestion.

Excessive misfire would generate a flashing MIL (malfunction indicator lamp) suggesting you stop driving. I'd be surprised if it weren't one of the suggestions already given.

Come to think of it, that much missing would probably have the CEL blinking (catalyst damage imminent).

Hmm, well Friday I replaced the plugs per the shops recommendation. 100% improvement, I'm wondering if the fluid and filter change took a few miles to be happy cause now the truck pulls hard and runs through the gears like it's supposed to.

Don't exactly trust it yet but if I can put a repair off for a while that would be nice.

Update since original. Plugs ($50) seemed to help but not 100% so I threw cap and rotor ($65) on it. More slight improvement but not right yet. Haven't been driving the beast much so this has all been slow.

Took on an two hour drive a couple months ago and fuel pump died so that was another $400.

Then the battery died (warrantee covered it though).

Last week I drove it and noticed that the miss had gotten really bad (still no CEL) and when I popped the hood to check on things I saw spark arcing from a plug wire to the exhaust manifold. Yesterday new AC Delco wires went on ($60) eliminating the last of the Accel crap that will never darken my cars again. So the motor finally appears to be running properly, YAY!!

So during the evenings drives it felt good and pulled well up to about 1/2 throttle. Beyond that it doesn't slip but it doesn't pull either. The engine will go to around 3,200 rpm and just stick there. If I let off the throttle it upshifts fine and we're good and motoring along all the shudders and misses and weirdness seems gone.

I don't think the trans is nuked but I'm not exactly sure what it is. Valve body? Shift solenoid? Are those the same thing?

Your Accel plug wires may have melted the catalytic converter.

Friday I took it to a exhaust shop to have the cat tested. They said it was fine. (FWIW)

Maybe fuel delivery issue? Did you change the filter with the pump change?

In reply to itsarebuild: No, and it's ancient I suspect so that's a good idea. I'll put it on the list.

Change the filter pronto. That's one of those things you do together. many manufacturers require you to put on a new filter at time of install for warranty cause a plugged filter will kill a pump quickly

All the E36 M3 in the pan are the steels worn out. There is no fix, but a rebuild.

chiodos wrote: All the above just dont have someone flush it or your only shooting your own foot off. Drop pan change filter replace lost fluid add cooler and pray. 4l60s arent known to be very strong anyways, kinda like why they have the moniker "4lE36 M3ty"

I still want to understand the logic behind dont flush it. This always bugs me as a guy who has done over 300 trans flushes in 8 years and has never seen it cause an issue. We use a fluid exchanger so the trans never sees more then its own front pump pressure and is never empty. Is this some old holdover logic? I flushed my wagon and 7 sets of rear tires later theres no issues. All of my personal vehicles including my wifes car are up to date on flushes. Most american car manufacturers still recomend a flush at 100k. Ive flushed cars on time and once flushed a buick with 240k miles on the original tar, err fluid. A flush wont hurt the transmission unless its already crap.