4R70W hard 2-3 shift at light throttle when warm

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brianl703

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I recently got a 1997 Ford Crown Vic P71. Here's what I know about it: It has a 1997 police transmission in it, and the odometer claims it has 261,700 miles on it. I have no idea if this accurate--title claims mileage is "not actual" so the cluster may have been replaced.

It shifts fine for the most part, except that when it's warm it sometimes has a hard 2-3 shift at light throttle. At heaver throttle, it shifts fine.

There are no codes and the fluid looks fine. I believe the fluid was recently (within the last 10k miles) changed, but I have no idea if it's the Mercon V it should be. It may well have Mercon in it.

I've reset the PCM this morning and it has not done it yet today, but it mainly seems to happen after lots of stop-and-go driving (perhaps the fluid needs to be at a certain temp for it to do this?)

Any suggestions?
 
Early pre-1998 4R70Ws are know to have problems with the 1-2 and 2-3 shift accumulators. They are machined out of aluminium with a o-ring at each end and they like to cause problems. Do you know if it was upgraded to current rubber molded steel pistons?
 
I do not. I know that it was in Virginia State Police service until 2000, and it appears to have the original transmission in it (although the serial number of the transmission does not match the last 6 of the VIN on the car--I don't think they usually do on Fords).

I suppose I should pull the pan off and find out.
 
serial numbers on Ford's for trans and engines do not match the VIN, which is why when people say they have a numbers matching Ford its a load of bull.
 
I found part # F7AZ7H292AB for the 2-3 accumulator piston. This seems to be a revised part.

According to one document I read, the 2-3 accumulator spring will just fall out when the pan is removed?

Quote:
o 4 - 5 items should fall into the pan; a little yellow plastic plunger (discard, it was atemporary plug from the factory), the 2-3 accumulator spring (set aside it does not go back in), a metal base for the spring (save), possibly the 2 – 3 shift accumulator itself (a larger plunger with a smaller diameter top and larger diameter bottom, and oval shaped filter.


So, to change the 2-3 accumulator piston will involve dropping the pan, and, if the piston doesn't fall out, remove it with pliers?

The 1-2 accumulator piston I know is held in with a snap ring.
 
Originally Posted By: brianl703
That makes sense. I've heard that the valve body bolts on these transmissions sometimes need to be retorqued.

Yup. The gaskets for the VB to Separator plate and separator plate to trans are like $3. Only thing is you need a torque wrench that can read 10ftlbs (IIRC) accurately. I bought a 20-200 in. lb. 1/4" wrench when I did the JMod on my trans.
 
I will keep the car, one of the reasons I got it is for my terrible commute to work.

The jmod is enlarging some holes in the separator plate, isn't it?

There's a Factory Tech Separator Plate I found by doing a search, seems to be a pre-drilled jmodded separator plate. I'm thinking about going with that so I can go back to the original unmodified separator plate if needed.
 
Hmm...I do have a scantool that can show transmission fluid temperature. Although the weather here has been the low 30s the last few days. I'll check that out later. Should just be able to unhook the return line from the radiator and see what flows out with the engine running.
 
I just checked the transmission fluid temperature during a 40-minute drive at mostly highway speeds..it peaked at about 141F. Hard 2-3 shift occurred with the temperature at 140F. I don't believe I have a cooler problem. Outdoor temp was in the 40s.

I know the transmission and motor mounts are worn out, I expect this could potentially be the cause of the issue?
 
Mine (1997 Tbird) has been doing the same...a bit - I have a suspicion that I might also need the 2-3 piston replaced.

should I get the 1-2 also replaced?
 
You can leave out the bottom springs in both accumulators for harder shifts. Thats what I did. Actually, if I did it again I would put a pink (light) spring in the bottom of the 1-2 to soften it a tad. The 2-3 accumulator even with no spring wont really make hard shifts though. I can feel it on my car, but it isnt at all like the WOT 1-2. I would call the 2-3 firm and the 1-2 harsh at WOT. Around town at more sane throttle positions I can just feel the shifts though. It is just about perfect. My only complaints at this point are when the computer shifts it, but thats a programming thing I dont have access to.
Now: http://www.youtube.com/watch?v=759UgAnAj4k
Before: http://www.youtube.com/watch?v=e-i3mkyEBI4
 
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