Raising the (un)dead 4r70w transmission

Messages
429
Location
California
Greetings! I've been gone a long while, but thought I'd come back with an update on the truck from this thread: https://www.bobistheoilguy.com/foru...overheating-failed-cooler-bypass-valve.302831

Vehicle history is in first post of that thread, with the addition of a 2-1 kickdown problem present the whole time that I sometimes confused with the 3-2 kickdown because I wasn't used to how the transmission felt in different conditions yet. 2-1 issue would only happen on the rare times when I really nailed the throttle at low to moderate speed. Transmission would appear to go into neutral, rev to redline if I let it, and then hit 1st with a BANG that chirped the tires and felt like I'd been rear ended. Taking my foot off the throttle in time would merely have a sloppy delayed shift. When coasting, manually pulling gear selector from 2 to 1 would have a noticeable hang time in neutral where 2nd was disengaged, but 1st had not yet hooked up. 4-3 and 3-2 shifts were all solid and smooth after the fluid changes and filter change I did back then at 172k miles. I was convinced there was a valve body failure making the 2-1 shift act up.

At 190k, I did a drain and fill with Valvoline Maxlife, as I had done before. I added Lubegard Red as well just to see if it would make any difference. 1500 miles later, I was forced to floor it at low speed to evade a dangerous situation, and to my shock, the 2-1 shift worked flawlessly! Thinking it was a fluke, I experimented more, and the kickdown problem never came back. I had all gears up and down under all load conditions and speeds. Transmission shifted just as well as the recently rebuilt one in the other work truck. Since then I drove it normally.

Then last Friday at 195k miles, the transmission suddenly acted up. A short surface street drive to the freeway and a handful of miles of cruising was fine, but once I got off the freeway, I was greeted by a LOUD whining noise when I accelerated. I could hear it over the AC and the radio with windows closed! The whine occurred in all gears, inaudible at idle, rising in volume with load and rising in pitch with rpm, also present at reduced volume when coasting, but going away when the torque converter locked. At the same time, every gear developed shifting problems. 1-2 would engage like a hammer, while 2-3 and 3-4 would flare and slip before engaging. Torque converter would lock up, but slip at higher load. Fluid was full and clean and didn't smell burnt, pan temp was 175F (normal as afar as I've seen) but it still acted like it was low on fluid or had low line pressure.

I limped it home maybe 5 miles, shifting manually to avoid shifts under load. I stopped at a parts store to get fluid and new filter, convinced the truck was done for. Dropped pan to find a magnet with fuzz and some larger slivers of metal, and a filter that looked pretty clogged. Changed filter and o-ring, buttoned it back up, filled fluid... and the problem disappeared. No whine and good shifts in all gears! It's been 350 miles since, including brutal winding roads in 100F+ heat, and a freeway mountain pass where it nailed a high load 3-2 downshift without flinching. If I'd showed someone the truck on Friday and again on Monday, they'd probably think I'd replaced the transmission.

Best I can tell residual debris from before I flushed the coolers and fixed cooler thermostat issue plus new material produced over time clogged up the filter and starved the pump. Whining noise was pump straining to draw enough fluid to keep line pressure up, therefore causing erratic behavior in all gears when they didn't have the required fluid pressure and volume to operate.

So I now have an undead work truck that I've brought back from what we thought were terminal problems twice now. How long will it go? Guess I'll find out!
 
Messages
5,478
Location
Ohio
How long? Probably not long. Metal filings stuck on magnet and a clogged filter, better get prepaired for its total failure.Clogging up a filter in less than 30k miles is telling you the transmission is on it last legs.The metal particles which don't settle in the pan will eventually get attracted to the shift solenoids as well where they will stay..
 
Last edited:

VeryNoisyPoet

Thread starter
Messages
429
Location
California
How long? Probably not long. Metal filings stuck on magnet and a clogged filter, better get prepaired for its total failure.Clogging up a filter in less than 30k miles is telling you the transmission is on it last legs.The metal particles which don't settle in the pan will eventually get attracted to the shift solenoids as well where they will stay..

Every transmission I've opened has had the ultra fine mettalic slime on the magnet. Some of the filter clog and debris was probably from the clogged coolers. I flushed them the best I could forward and backwards when I replaced the transmission thermostat, but there's likely still some crud in there being released. Larger slivers could have been from the 1st gear section since I did unfortunately encounter the 2-1 slam downshift a couple times since the pan was dropped the first time. Also whatever was dislodged that was causing the downshift to hang in the first place.

When I first took the pan off the magnet was completely buried in debris and even larger slivers of metal and that was way back at 172k. I'll post now and then about progress and if anything changes. So far continues to shift flawlessly despite the heat we're getting here in SoCal.
 
Messages
5,683
Location
Fort Worth, Texas
Most 4R70W/4R75W units go their whole lives without a filter change, If the filter clogged with debris......You have an issue!!

When we rebuild these.....We can tell they've never been serviced by the factory dipstick tube plug still in the bottom of the pan.
 
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