How to: Explorer Auto Transmission Diagnosis - Q & A FAQ

[Glacier991]

I think that fluctuation is suggestive of a boost valve problem. At this point about all I can suggest that you might do (which has a decent probability of success I think and will not need you to drop the tranny to see inside) is to do an actual full on rebuild of the Valve Body. When and if you do that, I'd replace the boost valve with the Sonnax upgrade.

Other thing that comes to mind is that your foreward clutch is fubar..... and that is a teardown item obviously. You have taken all the appropriate steps.... few shops would have gone the diagnostic route that you have.

 

[lihan161051]

Yeah, I can definitely say that if I hadn't been learning as I went along, I'd have probably approached the diagnostics differently.

There didn't seem to be anything out of sorts in the valve body when I took it out previously .. it'll have to come out again anyway when I'm disassembling, to get at the bolt for the center support, so I'll take another look in there. Boost valve didn't seem to be that out of sorts when I took apart the pressure regulator bore, all the spools seemed to be able to move about right. But you're right, I didn't do the full rebuild or replace any VB parts.

You think nominal pressure in OD but no clutch engagement is a problem in the VB rather than a fluid blockage between the VB and the clutch piston? I'd love for it to really be a VB problem, would save me about a week and a half of crawling around under the car. (now I'm wishing I had a good enough diagram of the separator plate to tell where the clutch apply pressures are fed into the case..)

 

[mike1471]

How do I know if the main control gasket is blown on my '95 4r55e? If it is, where is it, and how do I fix it? I was pulling my boat up a steep hill when the engine suddenly revved, and the tranny no longer does anything in any gear.

i had this exact same thing happen only it dumped all the trany fluid.
any thoughts on this before i let the mecanic start looking?...
blown hose to pump... gasket etc..

 

[Friction]

1-2 flare repair, looking for suggestions

I’ve been researching the posts on this page for a few days trying to better understand the problems in my own trans and get ideas for potential fixes. I have seen several other folks with identical issues on the forum so I apologize in advance if my questions has already been asked and/or answered directly.

The end-state for me is that I have had a minor 1-2 Flare for about a year now. When it started I took it to AAMCO and they replaced my overdrive and ‘another’ servo ( I forget the proper name of the other part) which did not fix the problem completely although it seemed to quell it for a while. Now the 1-2 flare is now a daily, although sporadic, occurrence so I went back to another AAMCO. They replaced the VB gasket (which was slightly pushed out near the reverse ‘piston’ opposite side from the TSB about the 1-2 flare) and ran checks on the electrical components based on a few TSBs. The problem is still there so they are suggesting a complete rebuild. The only error code to ever come up was an “incorrect gear ratio” code but I have only had that come up 3-4 times in the last year and only when I have had an increased load on the engine/trans during the 1-2 shift.

So I am looking for opinions on whether a new (remanufactured, http://www.valvebodyxpress.com) VBX type VB would be a probable solution or if a complete rebuild of the entire transmission is really necessary. I have done a lot of other “dry” mechanical work on my truck (i.e. brakes, wheel bearing, lots of electrical additions, ect) but other than installing an aftermarket trans pan and a new filter I have no trans experience so I need some help.

The AAMCO guys did not replace the EPC because they said it tested fine on their equipment even though I pre-authorized a proactive swap of the part as a troubleshooting measure. Leaving it in at 93,000 seems contrary to a lot of opinions on this board so I can’t help but question whether or not they are just “hoping” that a $1700rebuild is deemed necessary.

I'm in the military and I am in a little bit of a time crunch to get it fixed and drive home for the holidays before my next trip so I am willing to spend a little more to save time if it makes sense (i.e. buy a rebuilt VB instead of doing it myself)

Any thoughts on the best course of action?

Vehicle stats:
2001 4WD Trac
5R55E
93,000 miles (a few 1000+ mile trips towing a single bike trailer)
Trans fluid and filter changed at 35k and 90k (Mobile 1 synthetic trans fluid with generic filter from auto zone used both time, O rings installed!)
I have always driven it fast on the HWY but I generally do not accelerate hard from stops or abuse it in any other way.

Thanks in advance

 

[BrooklynBay]

Welcome to this forum! The name of the other servo piston is the intermediate servo. Before throwing parts at the problem, it's always best to do a diagnosis, and a visual inspection. Check the hydraulic pressure with a 0-300 PSI gauge. You could have low pressure from several causes, such as a bad EPC solenoid, bad VB gaskets, loose VB bolts, defective boost valve, clogged filter, etc. First do a pressure check, then drop the pan, and see if the bolts are loose. If they are, most likely the VB gaskets are probably shot as a result.

 

[Friction]

Thanks for the help, this forum is a life saver.

The guys at AAMCO dropped the VB and replaced the gasket (which had some damage near the Reverse piston) and buttoned the whole thing back up. Supposedly they ran a full diagnostic on it with no clear causes for the shift flare which is still present.

They want to do a complete rebuild which I am OK with if it makes sense. My issue is if it makes sense to go to a full rebuild in lieu of a VB modification/rebuild first. If the VB would have to be rebuilt in the course of a total over hall anyway, wouldn’t it make sense to do it first and see what happens since you can do it without dropping the entire system? Obviously there is the potential for wasted fluid and gasket costs but those seem minimal when compared to a $1700 rebuild that could be fixed with a $500 VB swap. The data throughout this forum seems to suggest a high probability for a VB issue causing the flare so I am willing to risk the wasted man hours/fluid cost if it is not the VB.

Does that make sense?
Could there diagnostics have missed a VB issue?
Would the clutch disks slip only between 1-2 gear but hold solid in the rest of them?


Additional data: My temp gauge shows some increase (10-ish degrees) when going up steep hills but nothing to significant if that is applicable to trouble shooting anything.

 

[Glacier991]

The fact you have a temp increase strongly suggests that you have a friction issue... you are slipping. The question is why.

The problems isolate themselves to a VB issue, or an issue with the band and associated components.

The VB issues are not just EPC.... there are a number of implicated parts. Your idea of replacing the entire VB is not a bad one.

What kind of care has this tranny had, fluid wise ? Also, have all TSB's been done ?

 

[Friction]

Thanks for your help

The trans has not been touched except for the servo replacement and VB gasket work that I mentioned above. Looking for the blown out gasket was the first TSB issue that was addressed. MAF sensor was cleaned based on another TSB but it tested OK before and after the cleaning.

I added an aftermarket aluminum pan to increase capacity and assist with cooling in Dec of 04 (approx 53k) I always use synthetic fluid (Mercon V) at changes (3 partial changes from the pan so far 53k, 74k, 82k, one dealer flush at 33k when Trans case was replaced under warranty for noise) fluid has always been in good condition, frequency of last few changes was based on trouble shooting the current problem. The only thing I have not been picky about has been the filters (only 2 of them) which have been the "best" that Auto zone has to offer.

I have made several cross country trips 2k miles towing an 8 foot single axle bike trailer and I do tend to drive a good pace on the highway (75-80ish when situation permits).

The temp increase is not noticeable around town, only when I drive through some long uphill sections of highway through passes, gaps, ect. (note- my temp sender is in the pan, not the outlet so I am only getting the cold side fluid)

My thoughts on the new VB would be that they would address the TSBs and known issues which is something I would want done in any kind of rebuild anyway. I got the link to VBX from one of Glaciers posts so I assume they are a reliable company. I can also get a rebuilt trans from Accurate Trans for $1400 which would cost nearly the same after installing it as having mine rebuilt, provided of course that the rebuild kit covers all the issues that present themselves. Any major component damage found in mine during the rebuild would tip the scales in favor of the commercially rebuilt trans but it would be to late at that point.

Incase this helps: The vehicle has a KN intake and Flowmaster SUV exhaust, no changes to the chip. I run royal purple in the coolant. I get consistent 455 (Evap system vacuum) and 401(low EGR input) ODB II codes. EGR system components have been replaced but the code still shows up occasionally (reset with a Scangauge II that is always hooked up). The Evap system is to hard to isolate a small leak in and not critical to the overall system so I let it go.

R/

 

[BrooklynBay]

You should have a heavy duty cooler if you do a lot of towing at high speeds up inclines.

 

[Glacier991]

People are starting to use this stickie as a place to post questions and problems that should have a thread of their own below instead of simple single Q general info types of questions.. I am going to close this thread for a while and prune out stuff that doesn't belong. IF YOU HAVE A SPECIFIC QUESTION THAT INVOLVES DIAGNOSIS OF YOUR TRANSMISSION, start a post below in the general section. Please. You will get more answers to boot. Thanks.

My idea here is simple one liner types of questions and accompanying answers.

 

[BrooklynBay]

This link has some good information on repairing transmissions, analyzing problems, and how to avoid future problems: http://gearsmagazine.com/images/issues/8_2009/2009_8_24.pdf