Reverse still a No Go

[William Wallace]

Hi all, I started a thread a couple weeks ago about reverse in my 4R55E out of a 1995 Explorer.
You can read the old thread here: http://www.explorerforum.com/forums/showthread.php?t=181051

So last weekend, I took out the VB, inspected it, replaced all the gaskets, solenoid O-rings, and put the D-style O-rings on the reverse servo, torqued everything down, same problem. It just sounds like somehow there isn't enough fluid pressure getting to the reverse servo chamber in reverse only (manual first and second work fine still). I was thinking it might be the pump, but if all forward gears work fine, then I'm starting to rule out that theory. Do you guys think one of my solenoids is going bad? I looked in the ATSG book to see what solenoid engages reverse, and the one that does (I forgot which one, and I don't have the book here at school with me) also opens up with other gears, which I have no problem in. If you guys have any insight, please let me know, because I'm running out of ideas.

 

[BrooklynBay]

Do you have a 0-300 PSI pressure gauge? Check your pressure in reverse. Your EPC might be bad. Did you check the spool in the valve body for reverse? It might be stuck. Did you replace the boost valve? There is no electric solenoid for reverse, only a low/reverse servo.

 

[William Wallace]

BrooklynBay,
I did not replace the boost valve. I'm reading around and that might be my problem. I could check the pressure in reverse, but it's pretty obvious that it's not getting enough. This boost valve though, does it come in other shift kits? Because I believe my friend said that he had a shift kit put in the thing a few months before he sold it to me, so if yes, then it might already have a boost valve in it. I'm looking at it though, and if it increases the pressure in reverse, then maybe that's something I should look into getting. At transmissionpartsusa.com there are two versions of the Sonnax boost valve, a 37947-01K and a 37947-03K. The 01K says OEM ratio, and the 03K says increased ratio. What ratio are they talking about, and which one should I go with? I'm guessing that it means pressure ratios, but I'm not sure. Also this spool you speak of, what exactly is that? Thanks for all your help. I'd really like this to be the last time I tear into this thing, so I don't have to keep buying transmission fluid.

 

[BrooklynBay]

Get the high ratio boost valve with the O rings. It has a little more pressure than the OEM version. High ratio is used with the 4.0L, but could be used with smaller engines as well. The shifts will just be a little bit firmer. As for spools, check the photo gallery for charts by Glacier991 by searching for 5R55. It's called the reverse modulation spool. Here is a picture from Glacier991's Photo gallery:

 

[William Wallace]

Ok, it sounds like I wouldn't have the boost valve installed. It doesn't shift that firmly now, and I know the bands and all are adjusted properly, so maybe therein lies the problem. Plus, I looked around for VB kits and I always saw the boost valves sold as a separate unit. Thanks Brooklyn, it might be a few weeks, but I'll be sure to let you know how it turns out once I get everything put back in.

 

[William Wallace]

Well, I put the boost valve in this past weekend, and my problem is still there. It's a little better, but it's still slow to engage, still makes that noise, and sometimes doesn't hold while I give it gas (although, it does hold better than without the boost valve). I checked the resistance of my EPC solenoid, and it measured about 3.5-3.6 ohms, which is in the lower half of the acceptable range (I think the lowest is 3.1 ohms). All the other solenoids measured about the middle or 5/8 of the way in their operating range. I'm not sure what else, maybe my EPC is bad. But if my EPC was bad, wouldn't it affect my forward drive (which works fine)? I'm not sure, I might end up taking it to a transmission place and let them listen to it. I just hope nothing happened internally, because I don't want to pull that thing again. Oh well, you gotta do what you gotta do. Thanks for your inputs.

 

[BrooklynBay]

Did you check the reverse modulation spool?

 

[William Wallace]

BrooklynBay,
no, I didn't check the reverse modulation spool. Are those weak points in the VB that fail often? Because initially after the rebuild, it worked perfectly. Then all of a sudden, this stuff happens. But after everything else, all fingers point at whatever controls reverse. Maybe I'll pull it again this weekend and check it out. But what would I be looking for? What would cause the spool to get stuck in the first place?

 

[Glacier991]

You could be having some pump issues. While not at the top of the list, when you have been doing ok after a rebuild, and then you lose reverse...the one thing that I know of that HAS caused those symptoms (from helping someone it happened to,) is that a new pump might not have had the stator bolts torqued down... as they back out and the pump leaks the first thing to go is the reverse.

Just a possible.

 

[William Wallace]

Well, I pulled the VB again, checked the Reverse Mod. Spool and no hang ups. I'm checking all my valves, and no problem, no siezes, etc. The thing that gets me is that manual 1st locks right up and drives, and that uses the low/reverse band. I'm looking at my ATSG guide, and in reverse, the direct reverse clutch is also engaged. Do you all think that this could be the source of my problem? Maybe a seal got kinked or rolled over and it's not sealing correctly? It says it engages in 3rd and 4th as well, but I don't recall having any problems while driving in those gears. Can someone verify that the direct clutch might be the culprit? I'll end up putting the VB back in this coming weekend probably. If the problem still exists, I'll end up pulling the thing out again and rebuilding again perhaps.

 

[oceanpimp420]

i had the same problem!!!

hello, let me start by saying thanks to every one on here you guys are life savers! ok my 95 XLT 4x4 with the 4R55E tranny i did every thing you stated above and i was jus about to replace me VB but then i talked to glacier one more time and he told me to just look at the reverse mod. valve area cause i hd every thing else working great but when i pulled the VB once again i brought it in the shop and compared evry thing wth a really nice print out from sonax "link" http://www.transmissionspecialty.com/parts/PDF/37947-Book(in).pdf i noticed that it looked like i was missing a L shaped retainer for the reverse modualtion valve so i made my own outta of a big paper clip and BAM the reverse worked and actually stayed in cause it would try to go into reverse before and it would but as u gave it gas it would pop outta gear so i'm telling u man chech for that L shaped retainer mine fell out while i sparyed down the VB with break clean so i'd say that retainer is very lose let me know if this is your fix i would love to hear that i was able to help someone save alot of time and effort better me than you. good luck!

Frank

 

[William Wallace]

thanks man, but all of my L-shaped retainers are there. It's just weird, because my valve body seems to be in good working order. No one has any insight on the direct/reverse clutch idea?

 

[William Wallace]

thanks for the idea man, but all of my retainers are in the VB, I've checked that everytime i've pulled it. That's what's getting me, the VB seems to be in good working order. No one has any insight on the direct/reverse clutch idea?

 

[Glacier991]

do you have all the forward gears? In the 4R and 5R what WAS called the reverse clutch is now called the direct clutch, and it is used in R and either 3rd (4R) or 4th (5R) so if you have those gears you can rule out the direct clutch.

I recently had a problem with an A4LD I sold. It was professionally installed and lacked reverse. I ascertained that we had manual 1st (band and servo ok) and 3rd gear (reverse clutch ok). That leaves VB. I sent a "NEW" VB (DAMN I hated to let that go but it was all I had at the moment) and... voila, problem fixed.

[That buyer got the best deal on the planet methinks, he bought the tranny as I rebuilt it - uninstalled - from a customer of mine and not only got one of the best 1994 A4LD's I ever built, but got a brand new VB in it to boot.... (and yes I honored my guarantee in spite of the resale almost a year later) that trans was better than new I think!]

 

[William Wallace]

Dang, that guy did get one heck of a deal didn't he. OK, I wasn't sure about the direct clutch theory, so I'm glad to hear that it's probably not the problem. My VB is sitting on my workbench, and I inspected it this past weekend and everything looked fine. No hangups or burrs or anything. The next two weeks are crunchtime for me with school, so I don't know when I'll be able to put the thing back in. I'll let everyone know what happens when I try it again. Thanks for all the help from everyone, I appreciate it.

 

[William Wallace]

I had time to put my VB back in the explorer between exams, and here's what happened: It still makes that whining noise when reverse is engaged. It engages quicker, but it's still there. I went to take it for a test drive, and after driving a few miles, I stopped, put it in reverse, and gunned it. It stayed engaged and backed up like normal. Then, I lost reverse, actually I lost all gears. I didn't hear anything break, it just wouldn't engage. So long story short, my dad and I tow it back to my house, check the fluid. Fluid is a little low, so I add some. It took a while, but the gears started coming back after cycling through them a bunch of times. I got reverse a few times, but it comes and goes. So now I'm thinking that I have ANOTHER problem electrically somewhere, since the gears are there, then not, then back again. I'm wondering if it's my manual valve position sensor. Does anyone have any specs on the sensor (like we do with the shift solenoids) so I can test it to see if it's bad? Thanks guys, the saga continues...

 

[BrooklynBay]

The sensor is analog from what I've read until 98 which was then changed to digital. I'm not sure exactly what the internal difference was. Did you check its alignment?

 

[William Wallace]

yeah, the alignment was in order. I took it off today to see if I could see anything screwy. When I rotated the piece that connects to the manual valve I only heard clicking (engaging a new internal contact) when rotating into 3 spots (neutral, reverse and park)...there are 6 different selections. I don't know if the units are made this way, but I'm probably going to replace it here soon just incase. I would just take it apart and see, but the halves are riveted on, and I'd just as soon buy another one.