[cgrey8]

My dad has a 95 Ranger with a 4.0L and whatever Ford stuck behind it for a 4-speed automatic that's now acting up.

TRS - Ford Ranger Automatic Transmission Identification
From the above, it appears all 4.0L Rangers with a 4 speed auto were 4R55E.

About a month ago, it started giving him shifting problems. It would work fine some days. Others, it would have problems shifting into 3rd from 2nd. It would either not shift at all or when it did shift, it felt like it was slipping. But here recently, it doesn't even attempt a 2-3 shift. For those familiar with how Ford transmissions fail, is this indicative of a mechanical problem in the valve body or a solenoid problem?

And how much could he expect to pay to get it fixed? He's too far away from me for me to do any diagnosis or work myself. So it'll have to be done by a local trans shop.

[LeadHead]

It could be a valve body or mechanical problem. Start with the VB. The solenoids (especially EPC solenoid) often fail, and the VB gasket sometimes blows out as well.

[cgrey8]

Can someone give me a Ford Electronic Trans 101 overview? For example, I don't know what EPC solenoid is (at least before I googled it) or why it would go bad more often than whatever other solenoids are in the trans, or why 1-2 shifts would work but 2-3 shifts would be affected.

I know Ford used 4R44E, 4R55E, and 5R55E transmissions in the Ranger/Explorers over the years. But I don't know how similar (or different) they are or how they are similar to the AODE, 4R70w, 4R110, E4OD, or whatever other Ford electronic trans models are floating around out there. Having a fundamental understanding of the similarities and differences might clue me in so I can talk more intelligently about them and ask questions that make sense.

Is there a website link that does a good job detailing these things out?

But back to the issue at hand, it seems the Ranger/Explorer transmissions are rather well known for 2-3 shift failures. One guy on an Explorer forum was even saying he was able to get the transmission into a state where it'd shift from 2-4 skipping 3 altogether but he didn't elaborate. Is that BS or is that actually possible with the way Ford made these transmissions?

Another thing the forums said is if it isn't a solenoid, it's likely a broken band. They said there's a band responsible for 2-3 shifts that when broken leave obvious evidence in the transmission pan. Is this common in Ford transmissions or just something that "could" happen and thus not likely unless the transmission is abused?

[85GT]

Baumann has some nice info on some of those transmissions. I use their early controller for my 4R70W swap.
http://becontrols.com/techguide.shtml

Also, if you google 'JMOD' there's a bunch of info on how to improve the 4R70 shift behavior. In Jerry's write up, he gives a basic explanation of how the circuits work in it. Others would be very similar. Stuff like servo's, accumulators, etc. It's on the TCCOA site. Jerry was the Ford design engineer for that and maybe other transmission from what I recall.

Sonnax is a good reference too. You could see if they offer any parts to solve particular typical failures.
An example is the Sonnax higher pressure main regulator valve for the 4r70. This would give a higher starting pressure for the EPC to control.

The EPC soloniod varies the line pressure as function of the amount of current sent to it. IIRC, it's inversely proportional. No current - full pressure.

[cgrey8]

I found Sonnax during google-searching and they did have some rather good info.

The most interesting was the history. The 4R55E is a heavier duty version of the 4R44E that has a 550 ft-lb torque capacity but very little about the design is different...just minor differences in components. Even the gear ratios are identical.

The 5R44E and 5R55E are just minor variants of the two 4Rs mentioned above where they basically just control the transmission differently to get a 5th gear out of it. But instead of taking advantage of this new 5th gear for the purposes of a widening the transmission ratios (lower 1st and/or higher 5th), all they did was just add a gear between the 4R's 1st and 2nd. The 5R's 1, 3,4 & 5 are the same exact gears as the 4R's 1,2,3, & 4. Thus there's no improved torque on take-off nor improved fuel economy on the highway. IMO that makes the difference between the 4R and 5R a gigantic nothing-burger but I'm sure Ford sold it as an upgrade. The valve body is even the same with the only major difference being the VB plate that routes fluid a little differently.


One thing that this site, along with a few others talked about was something they described as shift flare. What is that? I'd never heard of that term and their usage wasn't specific enough for me to glean what they meant.

[85GT]

My understand of shift flare, from various discussions on other forums, is when the RPM's increase during the gear transition. Essentially like the transmission is slipping during the shift exceeding RPM's of the lower gear it's coming out of.

[85GT]

Also, the second two digits of the trans ID eg.55 70, etc has to do with it's strength. I don't recall if it's actual strength rating like torque, or internal dimension size. GM does similar, 4L60, 4L80. I think one or the other indicates a diameter of the gear set or something like that.

[cgrey8]

My understand of shift flare, from various discussions on other forums, is when the RPM's increase during the gear transition. Essentially like the transmission is slipping during the shift exceeding RPM's of the lower gear it's coming out of.

That makes sense and that's what I was guessing it was. But I would've just called that slipping. But I guess they want flare to be more specific to automatics and slipping specific to weak manual trans clutches. Anyway, thanks for that confirmation on terminology. And incidentally, my dad said his transmission was doing that in between shifts when it was still actually attempting to shift.

I also found it interesting that the EPC solenoid runs full pressure with no control. That would explain why failing EPC solenoids might break bands in the process of failing. But I'm also guessing that if the EEC is monitoring the actual amount of current it is passing to the EPC, this is how it also knows the EPC has failed...by way of open/short circuit. Thus my guess is once the EEC detects that the EPC isn't acting right, it doesn't attempt shifts it knows it cannot do without causing transmission damage. But this begs the question, if 1-2 shifts are still working, do they not make use of the EPC? Thus is 1-2 shift firmness control done by some other solenoid?

Also, the second two digits of the trans ID eg.55 70, etc has to do with it's strength. I don't recall if it's actual strength rating like torque, or internal dimension size. GM does similar, 4L60, 4L80. I think one or the other indicates a diameter of the gear set or something like that.

In the case of transmissions that use bands, it'd make sense that the number might be related to the diameter of the drum the bands are trying to brake. A larger diameter drum would increase the torque capacity of the same width band tensioned with the same max pull-force.

[85GT]

Not sure why full pressure would break things. In the case of the Baumanator, the EPC curve goes to full pressure as you approach WOT. I recall similar happens in CBAZA though it is 'normalized'? in reverse in the bin. I think it's a failsafe should there be a soleonoid failure. And in the case of the 4r70 and jerry's write up, my understanding is the accumulators more so their springs temper the actual pressure to the drums. Much like a brake proportioning valve does.

[cgrey8]

Perhaps I was making a bad assumption about how the EPC was controlled. I assumed the EPC was modulated during the shift thus a light load shift would have a weak pressure gradually increased to some slightly stronger pressure upon a shift. And even at WOT, the pressure would be modulated from light to full pressure during the shift thus still delivering a firm, but smooth shift. So in my understanding, if the EPC was always applying full pressure because it was faulty then the moment the shift was initiated, the band would be slammed with full pressure potentially shocking it to the point that it broke if the drum it is trying to brake is under intense torque.

Is that not how the EPC is controlled? In other words, is it not modulated during the shift and instead simply is set to a specific pressure and stays there from the beginning to the end of the shift?

[85GT]

It's very possible in an EEC. My only experience is with the Bauman TCS. It appear to have a very simple implementation in the graphical user interface. One EPC curve of EPC current vs throttle position. Now if they internally do any modulation, i do not know. It would require setting up an oscilloscope to check. Don't have a DC powered one.

But I do know, the their controller and shift kit (before knowing about the JMOD), this is the cleanest shifting automatic I've ever been in. Gear changes literally like flipping a toggle switch. One instant in one gear then next you're fully in the next. It's just click, click click, then lockup. Not harsh at all, but then I only did Level 2 out of the 5 levels the kit offers. Yet still chirps tires at WOT. Hard to believe any modulation is occurring.

Decipha may have more info on the EECs. Pretty sure the CBAZAs only 'soften' shifts by reducing spark advance. But maybe they do more. Or maybe in newer EECs.

[LeadHead]

EPC is modulated during shifts, during converter lockup, park-drive-reverse engagement and more. The stock calibration very rarely if ever commands full EPC - even during a WOT shift. Max EPC is generally only commanded if a fault with the transmission is detected (such as excessive slipping).

A shift flare is different from slipping. Slipping generally means a certain gear is incapable of holding the engine's torque. A shift-flare generally means the gear holds fine, but the RPM's rise excessively before it shifts.

Shift flares are very common on the 5R55E because of how Ford achieved that extra gear over the 4R55. Ford simply applied the overdrive band while the transmission is in 1st gear. This results in a gear ratio between what used to be 1st and 2nd, and 3rd gear is what "2nd" was on the 4R55. However, this shift is extremely tricky because the 2nd-3rd transition requires the simultaneous release of the OD band, while the main part of the transmission is shifting into "2nd". If the OD band releases too early (which if often does), you'll get a sudden unexpected rise in RPM followed by a violent slam into 3rd.

[cgrey8]

Thanks for that clarification on both points.

And your explanation of what causes flare makes perfect sense now why they called it something other than slipping, because it isn't slippage. Given this delicate control work required just to get an intermediate gear doesn't make a lot of sense why Ford thought it was a good idea to market a 5 speed that doesn't add a heck of a lot of benefit. IMO if a transmission adds more gears, it should span a wider gear ratio range than a lesser-geared version so that either you get stronger take-offs and/or lower cruising RPMs in top gear. The 5R did neither.

Perhaps they were banking on a slightly better city fuel economy by being able to shift out of 1st a tad earlier or maybe some performance increase at WOT by staying higher in the torque curve. Granted a 1-2 shift @WOT on a 5R would feel stronger than a 1-2 shift on a 4R.

[LeadHead]

More "in-between" gears allows the engine to stay in its sweet spot more, and helps high-throttle acceleration by not having as much of a drop between gears.

I do however think the initial implementation of the 5R55 was pretty poor. Mainly because as it stood, the 4R55E was already a very close-ratio 4-speed automatic compared to other contemporary 4-speeds like the E4OD, 4R70W or GM's 4L60E. So that extra gear of the 5R55E isn't particularly useful. In fact, it's not even used below ~40-50% throttle or so. Most 5R55E equipped vehicles go right from 1st to 3rd unless you're really getting on it.

Ford later fixed those issues with the 5R55W, which brought 1st gear all the way down to 3.2:1 from the 5R55E's 2.47:1. That wide ratio gearset actually made 2nd gear useful.

[cgrey8]

More "in-between" gears allows the engine to stay in its sweet spot more, and helps high-throttle acceleration by not having as much of a drop between gears...

That's what I meant by staying higher in the torque curve.

...I do however think the initial implementation of the 5R55 was pretty poor. Mainly because as it stood, the 4R55E was already a very close-ratio 4-speed automatic compared to other contemporary 4-speeds like the E4OD, 4R70W or GM's 4L60E. So that extra gear of the 5R55E isn't particularly useful...

That was my thinking exactly too.

...In fact, it's not even used below ~40-50% throttle or so. Most 5R55E equipped vehicles go right from 1st to 3rd unless you're really getting on it.

I didn't know that.

...Ford later fixed those issues with the 5R55W, which brought 1st gear all the way down to 3.2:1 from the 5R55E's 2.47:1. That wide ratio gearset actually made 2nd gear useful.

Agreed. Change the rearend ratio to drop the RPMs a tad in OD while still getting a little better 1st gear, and you have a reason for adding that gear.

But this does make me now wonder, how similar (or different) are the 4R44/55 and 4R70w? Are they similar in name only or do they have some similarities in construction and/or parts?

And did they ever make a 5R70w?

[LeadHead]

The 4R70W and 4R55E transmissions are of a completely different design. The 4R55E is essentially a Ford C3 3-speed auto with a two speed (direct and OD) transmission stuck in front of it. That's what allows them to put overdrive on on top of other gears. The E4OD is the same deal, but with the C6 as its based instead. That's what allowed them to make the 5R110W 5-speed.

Those transmissions use the "Simpson" gear set, which only natively allows for 3 forward gears, so they need the extra OD unit in front. The 4R70W (and AOD) use the Ravigneaux gear set, which natively allows for four forward speeds. Modern 6, 7, 8, 9 and 10 speed automatics ditched the traditional Simpson or Ravigneaux gear sets in favor of more complicated compound gear sets usually involving 3 or 4 planetaries.

Also worth noting, the Chrysler 4x RE/RH transmissions used in their RWD vehicles through most of the 90s and early 2000s also used the Simpson gearset. But instead of putting the OD unit in front, they put it in the rear of the transmission. The downside to this, is that the OD unit must be much stronger. So the direct-clutch in the OD unit of Chrysler 4-speeds has a huge spring engaging the clutch, and the forces involved often cause the snap-ring keeping everything together to fail.