4r70w no forward gears, only reverse. help needed..
I have used this site for a long time but this is my first time having to post.
I have a 98 expedition with a 4.2 liter 4x4 and what I believe to be a 4r70w transmission (u code on the door sticker)
The original transmission went at 105k miles and was replaced with a new factory ford transmission by a ford dealer 3.5 years ago ($3800!)
the new transmission only has 10k miles on it.
Now the new transmission only has reverse. reverse works like normal but no forward gears. the idle will change when i put if in gear, but will not move, acts like it is in N . there is no strange noises,,
It's hard to believe a new trany is shot already, no towing, or off road use.
My question is : is there ANYTHING that can go bad that would cause this? The trany fluid is clean and clear bright red, and no burnt smell.
I want to check everything I can before calling a tow truck to have it looked at. I will have it repaired if needed, but I don't think I want to replace another tranny. Please any help would be great.
If there is a someone who repairs transmissions and has a lot of experance repairing this transmission and would not mind a 5 minute phone call from me please email me at email@example.com
To answer the question is there anything that can cause this, is yes there are a few failures that I can think of, but unfortunately they all have to with the forward drum and all of them will require the transmission to be removed and be repaired "rebuilt". Most of the transmission failures I see come through my shop are due to part failure and they can happen at anytime regardless of mileage. You should be able to find a shop to rebuild this transmission with all the goodies for 2 to 2500.00 with a warranty.
I'm sorry, I wasn't expecting to go to Transmissions 101 for people that are taking apart a transmission.
The manual valve is a machined aluminum spool valve located inside the valve body. It is mechanically connected to the shift linkage. It is not electronically controlled.
If the transmission shifts in and out of reverse you can be pretty sure that the manual valve is moving when the shifter handle is moved. If it didn't reverse wouldn't work, either.
In order to make a forward engagement the manual valve has to be moved to where it sends hydraulic pressure to the forward clutch, which is what the forward drum houses. Even if the electronics are completely disconnected from the trans the forward clutch would come on if the manual valve sends pressure to it.
Since another expert (probably correctly) diagnosed that the forward drum has failed, I can speculate that when the hydraulic pressure is sent to the forward clutch the broken drum is allowing the pressure to spray out into the pan instead of applying the forward clutch.
IIRC, this issue of a MANUAL LINKAGE in an Expedition has been brought up before.
IIRC there IS NO MANUAL LINKAGE into the xmission in this application.
It is all electrical, controlled by a driver shifting linkage to a multiposition switch on the side of the xmission. As I understand, from there it is all electrical thru a connector into the xmission.
Possibly the connector could be making a bad contact.
The following pictures proves just how manual the manual valve is, there is NO electronics involved with moving the shifter inside the vehicle that pulls the cable that moves the shifter arm on the side of the trans, that moves the linkage on the inside that is directly indexed in the manual valve.
The switch on the outside of the transmission tells the computer what gear has been selected, it does not turn the shaft to the selected gear.
The forward drum can fail or loose forward engagement and still have a good pressure reading in the following ways
A: Burnt clutches
B: Broken snap ring groove
C: Clutch splines stripped out
D: Stripped clutch hub.
His transmission is broke, there is no way around it, pull it out..
The knowledge, time and equipment it takes to properly rebuild transmissions and to stand behind your work is why they cost so much. If everybody could do it in there driveway in a hour it would be a lot cheaper.