4R70W Still No Reverse Warm Transmission Replaced

[dancssei]

Hello everyone,

I have been stalking this site for the past couple years and this is actually my first thread I have started. Glacier's threads have been very helpful throughout my work and I just wanted to thank him first! Thanks!!!

I bought a 2001 F-150 with 4x4 several years ago and within about 30 minutes of owning it I figured out that it didn't have reverse once it warmed up. I did test reverse before I bought it but it was cold. Anyways I did some valve body work and took many trans-fluid showers since then, but still no fix. I did seem to gain some ground by drilling the mod holes in the plate on the vavle body but it still wouldn't back up an incline.

Just last week I acquired an known good working (4R70W) transmission for a great price. Only problem was the output shaft was for a 2WD. So I tore down both transmissions and swapped out the output shafts as well as the forward clutches since the dood did some drags with it and they were getting worn. I also used the planetary and center support from mine because they appeared to be in better condition. Never messed with the valve body, just reinstalled it. The reverse servo was previously replaced in my tranny and same with the accumulators and pistons, so I used them.

Yesterday I finally got it all back together and still the same issue. I only put 12 quarts in and I know it calls for 14 but thats all they had on the shelf at 2am. I did change the transfer case (4406) fluid with 2 quarts of V as well. The fluid was dark and I was unsure about when it was replaced before (over 250,000 miles on vehicle).

Now I am unsure of what to do. I am reading about transfer case forks going bad, but I hate to open another can of worms. Reverse works fine for the first 5 minutes and then gradually loses power until there is nothing.

 

[PopRichie77]

It sounds like you swapped in a bad reverse part from your trans.

 

[dancssei]

Did a test drive today. I have engine braking in 1st, so I know for sure the band is good. All the other gears are still fine and shifting pretty smoothly, OD is working good and all the 4X4 gears engage. Reverse will not engage when hot the either 4x4 low or high.

I have thought it over quite a bit and I really think it either has to be the Torque Converter or the planetary gear assembly. I didn't see anything wrong with the planetary and it seemed to function and turn very smoothly.

I think when I get a chance on Monday, I am going to remove the transfer case, test for torque on the output shaft in reverse "hot" and see what happens. If that passes the test I will be looking into the transfer case, if not I've got another torque converter I could test out.

I kind of understand the torque converter's function but if it was bad I don't understand why the forward gears would be working. During the test drive today there seemed to be a little bit of noise coming from around the TC. Also I did drain it during the tranny swap.

Any thoughts, suggestions, and links would be greatly appreciated.

 

[PopRichie77]

The TC is working going forward and nothing would prevent it from working in reverse also. It is bolted to the engine and always turns the same direction. It wouldn't be a planetary gear assembly either, unless one was busted up. Transfer case maybe.

 

[dancssei]

The only other thing I can think of doing are changing the EPC solenoid or installing a longer reverse piston. I might try a pressure test if I can find some fittings that can adapt to my guage. If you know the exact size needed please chime in! Everything else has been changed or has nothing to do with reverse. I have noticed on occasion the speedometer will get stuck at higher speeds but it seems to be something with the cluster. I would give the dash a couple smacks and it would move.

I do have oversized tires on the truck and the speedo needs recalibrated, I have a manual to fix that but that is for another day far down the road.

Another question I have is PCM. Powertrain Control Module, where is it if I have one? I know people say reverse has no electronic parts, but quite frankly it does, hence the shift solenoids (#1 is on during reverse). I am wondering if maybe the wrong signal or no signal is being sent to the control unit, thus not allowing reverse. I know that a bad solder joint can work at first until it heats up, which seems to correlate with my problem.

 

[swetrid]

Fords symptom chart lists valvebody #6 shuttle ball, manual valve or main regulator valve concern. It also lists low reverse clutch, reverse band or servo as some posibilities. In my experience as Ford trans tech it is either valve body concern or reverse clutch. How are the rest of the shifts? Firm and good hopefully because reverse requires more pressure to operate and could be low line pressure from worn or weak pump.

 

[dancssei]

Fords symptom chart lists valvebody #6 shuttle ball, manual valve or main regulator valve concern. It also lists low reverse clutch, reverse band or servo as some posibilities. In my experience as Ford trans tech it is either valve body concern or reverse clutch. How are the rest of the shifts? Firm and good hopefully because reverse requires more pressure to operate and could be low line pressure from worn or weak pump.

The valve body came directly off a known good working tranny, didn't mess with it. So No to shuttle ball, manual valve, and regulator valve. Reverse clutch was also known good working, so no. Reverse band as well and it has engine braking in 1st, No. Pump came out of known good working tranny and seals were replaced, No again. All other shifting is fine other than sometimes a slight hesitation from a stop.

I just decided to start reading page by page everything in the ATSG manual. I reached page 9 were something just jumped out at me! There is a Transmission Operating Temperature Sensor (TOT). I am pretty sure I used the one from my old tranny.

Here is the description: It is a temp. sensitive device (thermistor). It sends a voltage signal to the microprocessor assembly. The voltage signal varies with transmission fluid temperature. The microprocessor assembly uses this voltage signal to determine whether a cold start shift schedule is necessary. The shift schedule is compensated when the transmission fluid temp is cold. The microprocessor also inhibits converter clutch operation at low transmission fluid temperatures and corrects EPC pressures for temperature.

(BINGO I think I am definitely on the right track now!) I am thinking the cold shift schedule is allowing enough pressure. Time for some electronic troubleshooting, perfect since I am an electrical engineer!!

And if this is the problem and I fix it, no techs are ever going to be allowed to say that reverse has no electrical concerns, plus there going to have to revise their manuals.

 

[PopRichie77]

Here is the description: It is a temp. sensitive device (thermistor). It sends a voltage signal to the microprocessor assembly. The voltage signal varies with transmission fluid temperature. The microprocessor assembly uses this voltage signal to determine whether a cold start shift schedule is necessary. The shift schedule is compensated when the transmission fluid temp is cold. The microprocessor also inhibits converter clutch operation at low transmission fluid temperatures and corrects EPC pressures for temperature.

You didn't find anything new, and what it's for is in your statement, converter clutch and EPC pressure, it only maintains the EPC pressure, so that it is the same when hot or when cold.
Has nothing to do with reverse not working.
Did you use an INCH LB. torque wrench on the valve body and tighten the bolts in the right order? Was the gasket new?

 

[swetrid]

I bet my wallet that the tft sensor wont fix your problem.

 

[swetrid]

Double ck sealing rings on the front pump for reverse.

 

[dancssei]

My first attempt on the original tranny I did do the valve body seals. I did buy a inch pound torque wrench just for the job. What is the correct torque? I am going to take a look at the old pump sealing rings and see what they look like.

 

[swetrid]

valve body is 80-97 inch pounds, front pump 18-22 foot lbs.

 

[dancssei]

I still am procrastinating on doing the job again, haven't had enough time yet and need a clean container to catch $60 worth of new fluid. Just trying to come up with everything to check before I dive back in. No I didn't use new seals on the valve body this time and I didn't tighten them in the exact order, but I did go in somewhat of a star pattern starting at the center. I did look at the old pump and the metal seals look ok.

I was thinking about unplugging the transmission harness to put it into limp mode to see if it made any difference. I want to test the filter too and make sure its not clogged. First I am going to get a couple more quarts of fluid. Also, I was tracing some of the cut outs on the case for the reverse circuits and I noticed that the harness enters the circuit and also the filler tube. Is it safe to assume if the seal on the harness or filler tube was bad I would be losing pressure?

I did use the old center support, can a bad center support cause my problem?

 

[PopRichie77]

Lets take a look at what you did. The original trans had no reverse. You got a working trans to replace the original, but the tail shaft was wrong, so you changed it, along with other parts, and the working trans now has no reverse. Logic would say that you transferred the bad part to the working trans.
The center support could be cracked under the bearing, did you put new seals on the center support, either one would cause leakage. You are going to have to carefully examine the parts that you switched as one must have the original problem. That's my opinion.
Good luck

 

[dancssei]

Today I topped off the fluid and still no reverse when hot. I started tearing it back down again. I just got the transfer case off and about half a quart of fluid dripped from the extension housing or the transfer case. It will probably be another couple days until I have the transmission out since I only have a couple hours a day to work on it.
Also it looks like I broke the bolt for the 4x4 shift handle, so I need to fix that too.


In the morning I want to test the shaft for reverse but I'm kind of afraid that fluid is going to go everywhere. Is fluid coming from the extension housing bad?

 

[dancssei]

I have the transmission tore back down, I was busy over the weekend so it just sat there. I did notice 1 difference on the center support. The original which I reused has an aluminum bushing and the spare is copper with 2 holes in it. A little bit confused as to if the holes are necessary.

Another issue I found was reverse servo I couldn't push it in at all by hand while the components were still in the tranny. Also when I finally got it out, the bore had tons of black buildup.

I may have fried the torque converter or pump as well. It seemed to be making some noise on the test drives. I thought for sure it was mounted correctly, but something must have moved before I got the transmission mounted (didn't have any assistance). Or it didn't like being completely drained of its fluids. I stuck a screwdriver in the shaft hole and the female splines moved around (had play and were not fixed to the center point), Is this normal?

I will post some pics as soon as I have time.

 

[dancssei]

This is the donor center support bushings, sorry there so dark.

 

[PopRichie77]

Sorry my last post about seals on the center support was an error the 4R70W has no seals there. If your sure the replacement trans had reverse, I would still say you moved the bad part.
Some one else that is more familiar with the 4R70W needs to help you.The AODE is similar but I haven't worked on one of those in years.

 

[PopRichie77]

Your sure that the steel seal rings on the pump stator are good and also the inside of the reverse drum where they ride. Are the Seals in the reverse drum good and the piston is not cracked?

 

[dancssei]

Got it working finally. I went ahead and changed out the planetary, center support and reverse clutch drum. I think the problem was the seals in the reverse clutch drum. Initially, I replaced the reverse clutch pack because they were worn, but evidently not the whole problem. So now everything seems good.

I used the flywheel and torque converter from the donor since my tc was making some noise.

Now it seems like I created another problem. It doesn't want to shift to 2nd without letting off the gas. First thing I thought was the solenoids, any ideas??? I was also considering putting the original valve body back in.