Hey gang,
I have a 98 Expedition 4.6L 4WD which has a 4R70W transmission and 251k miles on the clock. It has been having issues shifting from 2 to 3 lately. Other shifting and driving is fine. From reading, it sounds like it is most likely the 2-3 accumulator. I am planning on removing the valve body and replacing that accumulator assembly and wanted to get any thoughts on what else I should be replacing while I am in there. Beyond dropping the pan and replacing the filter, I have never worked on the internals of an automatic transmission before. However, I do have the Ford Workshop Manual for the truck. Here is where I am at:

• Transmission must stay in the truck
• Replace the solid internal wire harness
• Replace the EPC Solenoid, TCC Solenoid, and Dual Shift Solenoid (all come in a kit)
• Replace 2-3 accumulator piston and springs (read that this spring is a common failure) with parts from Transgo shift kit

Any other thoughts as to what I should look at or replace while I'm in there?
Much appreciated!
Craig

 

I replaced everything ( except the electronics) at 140k and put in a shift kit: https://www.f150online.com/forums/tr...rvo-4r70w.html

 

Thanks for the reply. I have been doing a bit more research and also read through your post. How are you liking the Transgo kit? In addition, I am also thinking about adding the Sonnax AODE4R75EZIP kit, which has new OD servo pin, main pressure reg valve, boost valve, 2-3 valve end plug, bypass clutch control valve kit, OD servo regulator valve, and a bunch of other parts.

So here is a tentative parts list:

1. Borg Warner solenoid kit
2. Hard wire harness (I'm assuming this will crack when I pull it out, given its age)
3. Bonded Servo Piston Kit Complete New Package Four (4) Piece Kit
4. Sonnax Zip Kit
5. Transgo SK shift kit
6. Wellington Parts 4 piece valve body gasket set

The one thing I don't see in either of those kits is the retainer clips which hold the OD servo and 1-2 accumulator. I have read the OD clip can be an issue.
This tranny has a lot of miles on it, and I'm not really looking for anything beyond it working how it should. This is over $300 in parts not counting fluid, but I guess since I've never had any trouble with it before now, I'm still money ahead.
I'm debating whether the Zip Kit really buys me anything (do all of those valves need replacing?), esp if I am using all new springs from the Transgo kit.

Any thoughts?
Thanks again.

 

I liked the kit ...... and it held up with time. I had a reverse issue crop up just a few months ago, but it sailed trouble-free with 120,000 miles on the transmission after the mod.

These transmissions burn out the overdrive band coming from the worn valve in the valve body. The Sonnax upgrade seems to address the problem well.

Good idea to go through it all and make a sound(er) transmission... . If you can do the work, go for it i say. Even it didn't forestall a future trans failure, it will shift firm and nice. Reverse is quick on engagement, too. The stock configuration seems lazy.

All in all i sold it and bought an '18 F150.