Issues with 4r70

[bmxking5]

Ok. Some of you know that I bought a 96 explorer with a 5.0 about a month ago. The transmission was rebuilt 7 months ago, but was only driven for a month of that time and has less than 1000 miles on it. I drive it most of those miles (it only had 50 miles on the transmission when I got it) and it shifted really slowly/softly (took 2-3 seconds to fully shift). I had assumed it was just the way the stock transmission shifted, however, knew it should have some firmness when shifting especially considering it was newly rebuilt. Finally 2 weeks after purchase, 3rd gear started slipping and then went out completely. I called the previous owner and shop and they said they'd rebuild it if someone paid again b/c it was out of the 6 month warranty. The previous owner paid for the repair (although I didn't want to use that shop again, cause they obviously don't know what they're doing...but I was hoping for the best since I wasn't having to do anything more than pull it and wasn't paying any extra) and I reinstalled it yesterday. I filled it up and it is still experiencing the same problems in just a matter of 2-3 miles.

The fluid was full when I purchased it and was easy to see that it was all new. I drained the fluid when I pulled the transmission and it had metal flakes (but not nearly as bad as I expected for completely losing a gear), They definitely took the transmission apart when it was at their shop, because it took the full amount to refill it. I cleaned the lines and cooler before installation of the so-called repaired transmission and there weren't any signs of blockage...radiator is new also. Any ideas on what could be wrong??? I'm thinking it is some kind of valve because it acts like it doesn't have enough pressure to shift (like it's low on fluid)????? I have a little experience with transmissions and rebuilt my 5spd, but don't know a whole lot about automatics. If anyone has any kind of input it would be much appreciated. Thanks a lot, Bryan

 

[bmxking5]

bump

 

[mechanix]

I would try to pull a pressure gauge on the line pressure port while driving and see if you loose all the pressure when it shifts into 3rd gear. This will tell you what way to go as far as a repair. I have seen many of these trans break the springs for the accumulators. There is the possibility the 2-3 shift piston is bad and causing a pressure drop. You can fix that by removing the valve body and pulling it out and installing a new one. I would like for you to get some more input from others here, but this is the basic stuff. Right now I am rebuilding a 4R75W, the 4R70W big brother. If you need any pictures of how things go together let me know.


Eric

 

[bmxking5]

Okay, thanks a lot. I'll look into doing that. Any idea where I can find out what pressure it should have while driving/shifting/etc.

 

[mechanix]

Okay, thanks a lot. I'll look into doing that. Any idea where I can find out what pressure it should have while driving/shifting/etc.

Some place I found a diagnostic to check the pressures and stall tests. But I can't find the link. I will try to find it and post it.

http://www.mediafire.com/?bpf5czmgbjl

Just click on the link and download it. It is packed with alot of good info.

 

[bmxking5]

Hey I downloaded that and it was pretty helpful. Found everything like that for my 4r70 on Alldata and just now bought a MAC transmission pressure gauge. I tested the pressure in all gears at idle and wot stall. The idle pressures are right in spec. The WOT pressures are definitely low. Reverse spec is 207-267 and it's 120. OD, 2, and 1 spec is 160-210, and it doesn't go above 70 at WOT stall. Almost everything I've looked at points to the valve body. Any ideas on what else I should check before dropping and the pan???

 

[mechanix]

Hey I downloaded that and it was pretty helpful. Found everything like that for my 4r70 on Alldata and just now bought a MAC transmission pressure gauge. I tested the pressure in all gears at idle and wot stall. The idle pressures are right in spec. The WOT pressures are definitely low. Reverse spec is 207-267 and it's 120. OD, 2, and 1 spec is 160-210, and it doesn't go above 70 at WOT stall. Almost everything I've looked at points to the valve body. Any ideas on what else I should check before dropping and the pan???

Bryan

Looks like your pressures are a bit low. I think in the 90's Ford had an issue with the EPC solenoid. It would fail and cause low pressure. Now being that the trans shop rebuilt this trans twice I would assume they didn't miss any of the lip seals on the clutch packs causing this issue. Also in my readings I didn't see of any issues with the VB gaskets blowing out like in the 4r55. I would drop the vavle body and check to make sure there are no chucks of poo in the passages. Might be a good time to install a shift improver kit too while you are in there. Do you have a break down of the valve body? If soo look for the boost valve. I think in the manual I have it says this some times will stick and give a low pressure condition. I wish I could be more technical and help you, but I am not very familiar when it come to diagnosis of trans, I am just able to rebuild them. Go figure. Keep me posted.

Eric

 

[bmxking5]

Alright, yeah I have yet to hook it up to the EPC fitting on the passenger side of the trans cause I think I'll have to drop one of the exhaust pipes, but I'll try again tonight or tomorrow now that the exhaust is cooled down. I'll let you know what it reads. After that I guess I'll drop the pan and do an air test (found that on Alldata as well) and go from there. Really appreciate the help, hopefully I can fix this thing fairly cheap instead of having to get another unit or pay someone else to fix it again. Thanks again!