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Dieseljunky2, Ford Mechanic
Category: Ford
Satisfied Customers: 3946
Experience:  ASE Certified, Ford Certified, Cummins Certified, & 20+ years in field experience
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My transmission is slipping but only in reverse..hill..under load

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My transmission is slipping but only in reverse and when going up a hill. In forward, it is totally fine. Other than slipping when under load, there are no other symptoms. What could it be?

99 Ford Explorer, XLT, Auto trans, 4x4, 6 cyl.
Hello, you say it only slips going uphill in reverse, and pulls fine in all forward gears? Silly question time, have you made sure the fluid level is full with the trans warmed up and the engine idling? Also, was the cooler either replaced or flushed out when the trans was rebuilt?
Customer: replied 7 years ago.
Both before the overhaul and after, it makes no difference if it is warmed up or not. Same results either way. I do not think the cooler was flushed. I assume the fluid is ok because the shop has been working on it and is puzzled with the problem.

A little background. I am in Central America doing volunteer work. The auto trans mechanics here are mediocre. And, my spanish is mediocre. So communication may not be totally accurate but I think it is pretty close. I am hoping if you can diagnose the problem, I will buy the parts and the mechanic will do the work.

Here is a brief summary.

1. It slips but only in reverse. In forward it will climb a steep mountain.

2. It only slips when under a load. For example, it won't back up a hill. It will not back up over a street curb. The motor revs but the car does not move. But, on flat pavement or with a slight uphill grade, it backs fine.

3. There are no other symptoms. No strange noise, shifts fine, etc.

4. The transmission has been rebuilt. The mechanic saw worn parts and replaced everything included in the kit he bought.

5. The mechanic examined the transfer case and saw no problems.

6. The mechanic says the transfer case has some electronics that he does not fully understand. He thinks those electronics are the cause of the problem... maybe a sensor of some sort. If I understand him correctly, he says the transfer case has a magnetic gismo that activates the clutches that control reverse. He thinks the magnet is week and not putting sufficient pressure on the clutch disc. I think he is a good mechanic and sincere in his effort but this problem is just over his head.

I have limited internet opportunity so my replies may be delayed.

The magnetic clutch in the transfer case is to engage four wheel drive. It has nothing to do with shifting. Is there any way your mechanic could scan the computer for codes? I am looking up your truck for trans issues, will reply back soon. Thanks

Hello again, I looked into the problem some more. I think youmay have a problem with the low/reverse servo piston or rod. These are selectable by length of the rod. If your system is at the end of the tolerance, it will allow slipping. Here is the chart for the rod length of the piston. This is located in the trans pan and can be replaced by removing the 4 bolt cover that holds it in place. If you have no codes, I would start by installing the next longer piston assembly. A longer piston, will give more holding power in reverse, but you must make sure that the band fully releases. Your trans guy should be able to check this out.



Length - mmLength - inchesIdentification
54/532.112/2.0851 Groove
51/502.014/1.986No Groove
49/481.915/1.8882 Grooves

Customer: replied 7 years ago.
There are two codes showing. C1102 & C1145. Could these be related to the trans problem?
Customer: replied 7 years ago.
I have a photo of the piston and rod to send you so you can verify it is the correct part. It was the only part we saw with your description under a cover with with four bolts. The reason for the photo is because the dimension is considerably different than you described. You described a rod 48 to 54 mm. This rod is 70+ mm.

Did the two codes I sent you mean anything? C1102 & C1145

Customer: replied 7 years ago.
To save time, in case you need it, the VIN is 1FMDU34E7XZA89502 and the motor is the SOHC, 210 HP

Could you please verify what transmission you have in the truck? The manual says that you have a 5R55, but your vin number says that you have a 4R70W. I need to know which you have? The longer rod, how many grooves does it have near where the piston is atached?

Customer: replied 7 years ago.
How will the mechanic know what trans I have? Wouldn't the VIN be more accurate?

What about the two codes I sent you. Could they be related to my problem?

I could not remain any longer in the town where the mechanic lives. I have volunteer projects that can't wait. I will get back to see the mechanic next week. Maybe by phone, I can get the trans ID # XXXXX you think the VIN is mistaken.

The difference, is a 5r55 has a rectangle shaped oil pan. The 4r70w has a square pan with the back two corners angled inward. The two codes, are for The right front abs sensor and the g-force sensor in the truck. Neither of these affect trans operation.
Customer: replied 7 years ago.
The pan is rectangular.

This is the picture of the low reverse servo for the trans you have.

This is the cover and bolts to remove

Customer: replied 7 years ago.
I can't open the pictures.

Does this trans have a reputation for problems or a reputation for being durable?

Another trans mechanic here said that even if the low reverse servo pump was working correctly it would not be sufficient to move the truck up a hill in reverse because is lacks the power. He said the reverse depends also on the power of some of the high gear apparatus. Is that accurate?

The most common issue is with the low servo. This trans is the weakest of the available transmissions for your vehicle. If everything is working correctly, the trans will pull just as strong in reverse as it does in forward. .
Customer: replied 7 years ago.
Can you repost the pictures?

Because it will pull just as strong in reverse, does that mean the power is coming from the low servo? Or, is the low servo supplying some of the power and some of the power comes from other places?

I will not be at the location where I can access the pictures until tomorrow. Yes, the trans uses some forward components for reverse. I will also post you an application chart at the same time as the photos. this chart will show what components are used in each gear. but, I am not at a computer that can access them right now. Thanks
Customer: replied 7 years ago.
Tomorrow will be fine. Thanks


Customer: replied 7 years ago.
The "photos" show nothing except a "?". When I click on it, it takes me to a blank web site with the same little "?". If you think it would work better in email, send to me aXXX@XXXXXX.XXX

All email addresses are blocked, try and download now, maybe it blocks it after a time period. Thanks


Customer: replied 7 years ago.
Same blank screen.

I volunteer here with Art For Humanity. My e-dress is glenevans @ artforhumanity . org

By separating everything maybe it won't be blocked.
I am going to see if one of the other experts can send you the info. Evidently, I have a different operating system. I am going to opt out, someone should be able to help you shortly. thanks
Customer: replied 7 years ago.
Is there a way to test the reverse servo without taking the trans apart again? For example, is their a port that he can put a pressure gage to determine if the the reverse servo is suppling sufficient pressure? Are there other ports where he could check the pressure from the other areas that supply assistance in reverse?
Customer: replied 7 years ago.
When you say you are going to "opt out" is that temporarily for someone else to send the pics or permanently? If it is permanently, before you leave, I'd like to "accept" so you are compensated because you have offered helpful info. But, if I "accept" does that end my conversation on the topic? Just let me know. Thanks


Let me know if this one works?



Band/Clutch Application Chart No. 601

GearFront BandIntermediate BandLow/ Rev- erse BandForward ClutchDirect ClutchCoast ClutchFront One-Way ClutchRear One-Way ClutchEngine BrakingTCIL
Man 2nd (3rd gear) A A AHORORORYESNE
a Overdrive Cancelled CANCELLED
b PCM Controlled

A = Applied

H = Hold

OR = Overrunning

NE = No Effect

Customer: replied 7 years ago.
Got it. Now how about the photos of the servo?
  1. Remove the transmission pan. For additional information, refer to Fluid Pan, Gasket and Filter in this section.
  1. Remove the transmission fluid filter.
    1. Remove the transmission fluid filter screw.
    1. Remove the transmission fluid filter.
  1. Remove the low/reverse band servo cover.
    1. Remove the low/reverse band servo cover screws.
    1. Remove the low/reverse band servo cover and gasket. Discard the low/ reverse servo separator plate cover gasket.
  1. Remove the low/reverse band servo piston and rod and the low/reverse band servo piston return spring.
Customer: replied 7 years ago.
Still no pics
Customer: replied 7 years ago.
Your inspection instructions seem to me to rely on a visual inspection. He may not recoginze the problem if he sees it. What about my idea of plugging in a pressure gage and checking to see if the servo is putting out sufficient pressure? Is that a possibility? It just seems to me that most any sophisticated hydraulic pump, (which I assume is what a auto trans is) would have ports where pressures could be checked as part of trouble shooting.
Reference: Line Pressure Chart
Trans.Transmission Model/ApplicationRangeIdle 1000 RPMWOT Stall
5R55E4.0L EIR55-65175-215112-134282-350
4x2, 4x4(D) 2, 125-3580-110112-134228-263
5R55E4.0L SOHCR55-65175-215112-134282-350
Explorer/Mountaineer 4x2/4x4N20-4075-120
(D), 2, 140-50100-135112-134228-263



Line Pressure Test

ItemPart NumberDescription
1 - Line Pressure Tap

ItemPart NumberDescription
1 - Electronic Pressure Control (EPC)

Dieseljunky2 and 2 other Ford Specialists are ready to help you
Customer: replied 7 years ago.
2. Ques. 1. Do you think you will be able to post the photos in a way that I can see them? I can see the graphs but not the photos. 2. If I end up buying a rebuilt/remanufactured trans in the States and shipping it here, what is the best trans available that will fit exactly w/o modification? You said the one I have is the weakest. Which is the strongest?

I don't know why the pictures won't show on your computer. I have sent them on 3 different systems. AS for the replacing it, the only thing that will work without major modificatins is the trans that you have already.
Customer: replied 7 years ago.
Maybe the picture problem is with my computer. Thanks for your help. I will say goodbye and "Accept". I wish for you all the best.