4R70W...if truck coasts the tranny then slips

[mnealuf]

I have a 4R70W with 130k and lately I have noticed sometimes when I decelerate (like coasting thru rough intersection at around 30 MPH) and re-apply the throttle the tranny slips like crazy then up-shifts and acts normal. Only does it when it coats and then acts like it downshifts when it should not have or slips badly, not sure which. Any thoughts?

Oh one more thing , the fluid was changed about 3 times (had a 1-2 accumulator and TCC issue) about 7k ago (thanks to Glaicer and good folks here who helped out) . Curently it is clean, full and not burnt. Not showing any codes.

 

[mnealuf]

Bump...anyone??

 

[Turdle]

It kind of sounds like the torque converter.

 

[BrooklynBay]

Have you replaced the EPC or the TCC solenoids?

 

[mnealuf]

I had some issues right after I bought the truck (used) about 10 months ago, it has 120k on it then. Guy I bought it from said the tranny supposedly was re-done at 115k by local shop. Anyhow about 3 wks of owning it I had a a issue where the TC was staying locked up, after some help of good folks here and Baugham (sp?) controls I replaced the TTC, problem solved. Then about 2k later had a code flash, 1-2 shift error. Replaced 1-2 accumulator piston and cap but no change still had the error , then I replaced shift solenoid block and no codes. No issues until now, actually once the truck did this exact same thing right after I did the solenoid block, but just did it once and was not 100% if it slips or what it did. (thought/hoped it actually downshifted and was just free-wheeling the RPM s to match the speed of the truck)

I believe the local shop did a crappy soft rebuild and reused all the electronics in the VB. I didn't like the fact that they did not even use the updated 1-2 piston etc. Think the EPC is next likely suspect? I have heard something about the one way clutches in the older 4R70W being weak link, please forgive my ignorance but that is on front side of the planetary gear set? Since truck is 97, I have older transmission and weaker clutch I guess.

Have you replaced the EPC or the TCC solenoids?

 

[BrooklynBay]

Did you read the sticky thread by Glacier991 called the 4R70W rebuild diary?

 

[mnealuf]

I have read it, I read it back in the day when I was first having issues and learning about the 4R70W. I believe at that time he was adding to it slowly though so perhaps a re-read is in order?

Did you read the sticky thread by Glacier991 called the 4R70W rebuild diary?

 

[mnealuf]

I re-read it last night and sure enough he has added some info to it. Lots of good stuff there for sure. I would be lying to say I absorbed it thoroughly the 1st time thru. I had a guy on another board reply to the issue and said it sounds as if the one way clutch is still old style and is on way out. He also thought once they start to go get ready it is quick and painful death. The truck has not done it in a couple days and there was literally months between 1st time I experienced it and this time so not sure . (typically mechanical things are more constant IMHO) But then again I might be just wishing for best to avoid a couple grand rebuild. I actually might trade truck, we are talking about how nice it would be to have a a quad cab and this truck is worth about the same $$ with and without a 2k tranny rebuild. I do enjoy no truck payments though.

 

[mnealuf]

I have not had the issue in about 2 wks of driving again, transmission shifts fine. I only drive about 4 miles to work but all city and thru the inter sections that make the tranny slip, and quite abit of weekend driving. I wonder if the one way clutch would be to intemittant. Any thoughts from BB/Glacier or the other ones in the know?

 

[BrooklynBay]

I know that you mentioned that you replaced the 1-2 accumulator. Another part might have been binding, and started to work correctly. A valve body rebuild might be a good idea to get rid of the problem. Continue driving it, and see how it is. If the problem doesn't come back, then just consider yourself lucky.

 

[CDW6212R]

If you are going to keep the truck, do something with the trans before it completely goes out. Most of all if and when a failure begins, stop driving it. After initial trans failure the damage which occurs ongoing is what creates a failure sooner in the future, it is extremely hard to completely fix a "burned up" transmission.

That being said, either sell it or install a valve body kit. Has it had any kit installed in the valve body? I'd hope not, and do a kit, plus any solenoids which could be related to the symptoms. The system corrections kit that Transgo sells is around $40, they make a real shift kit that's over $100. I like them both, but the shift kit makes for a more fun vehicle. Good luck,

 

[mnealuf]

As far as I know there has never been a VB kit installed, it is stock. I also own a Explorer with the 5R55E and knew of the VB issues with those but thought (hoped?) the 4R70W VB was better. I guess a kit & EPC would not hurt. (I have replaced the other electricals in VB other then the EPC) . There again I knew the in the 5R55R the EPC was a common failure item but thought I was in better shape. I am aware of the rapid sever degradation of a slipping/failing transmission and will cease driving it as soon as it slips. When it slips once every couple months it is hard to justify selling it......better knock on some wood as I type this

 

[CDW6212R]

Cool, the AOD has evolved since 1980 when it started with a horrible reputation. The last few years of the 90's it has been the opposite. I don't know if the EPC is as much trouble in the 4R70W as the 5R's etc, but I don't think so. I have two 95 Crown Vics with an odd 1-2 shift characteristic, both since different shift kits. The EPC isn't a bad idea, I wonder if they are cheaper than the 5R55E solenoid?

Install a kit in it then, the solenoid, and add an additive from Lubegard. Regards,

 

[Glacier991]

The VB in the 4R70W is not the problem it is in the 5R55E. The EPC solenoid (made by Borg Warner) is not subject to the problems as the 5R55E EPC is (made by Bosch). Whereas in the 5R55E I usually start out suspecting VB issues, in the 4R70W that is about the last place I go hunting.

In fact I think about all Sonnax offers for the 4R70W is a pressure regulator spool and pring and in later years an OD pressuire regulator. THAT speaks volumes to me. [If Jerry the Sonnax Prez. reads this... I will buy lunch for a chance at your brain on a multitude of issues]

What you describe sounds predominately a pressure issue. The 4R70W has a ton of pressure ports....(love em) and before I spent BIG bux on a repair.... I'd invest the $100 or so for a trans pressure gauge to see what is going on.

My initial thoughts are headed toward pressure leaks, or a failing pump.

 

[mnealuf]

So if it is a failing pump , would it be possible to be intermittent? Please forgive my ignorance but it has gone several weeks again with no slipping. I have seen the pressure tap ports in the "rebuild" diary and would I hook a mechanical gauge to them and run into vehicle interior? Perhaps I could use a electrical oil pressure gauge (easier to run/manage wire then hollow tubing for a mechanical gauge)