slipping trannie

[mrthuse]

'99 Ranger w/ 6-cyl Automatic @ 170K miles...

Trannie started slipping about 6 weeks ago after a slow reverse out of a parking space. The first 10 seconds in drive slipped, then finally engaged. Indicator lights for O/D and just about everything else lit up like Christmas. Brought it to my mechanic of 30 years. He hooked it up to his computer which diagnosed a bad speed sensor. He replaced the part, lights went out and all was well until a couple of weeks ago.

Same scenario: slow backup out of parking space, trannie slipped in drive, though no indicator lights this time. Apparently, this only happens after a slow reverse - I tested it out by giving it a little gas and getting it up to about 5 mph in reverse. No slippage in drive. Returned to my man who drove the Ranger and discovered the same thing. He replaced the speed sensor again; no improvement. He advised replacing the entire trannie given the mileage.

Decided to mull all this over ($$$) and mentioned it to a friend who offered that the problem might be the torque converter. My mechanic agreed but was hesitant to do the work. He said he'd have to drop the trans, open it up, replace the torque converter and put it all back w/ not much assurance that the fix would be the end of it. If it's not, we have to do the whole thing again to replace the entire trannie and that's more $$$.

He agrees the slippage could indeed be the fly wheel not properly engaging the torque converter, but wants to do the job as economically as he can.

Any thoughts?

 

[Explorin94]

I agree with the torque convertor being bad, but I also agree with your mechanic and have him replace the trans with the miles on it.

 

[mrthuse]

So it's worth the expense (+/- $2K) to do the job, assuming I want to keep the beast for 3+ years?

 

[86ford]

here locally i have had good luck with getting transmissions replaced cheaply ( around 1000 bucks) because my local shop i take my trans jobs to ONLY does transmissions, rearends and t-cases. they are quick fair and give a warranty. research your local shops that do ONLY transmissions because there quality and price will most likely be the best ( avoid chain stores!)

86

 

[snake]

Check the filter first! Could be clogging. It is NO WAY the flywheel is not "engaging" the converter, as they are bolted together and would raise hell if they came apart- not to mention it wouldn't move. Converter might be bad tho. I think I'd find a guy who is qualified and specializes in tranny repair. Could be as simple as a electronic servo going bad.

Edit: you don't have to "open up" a transmission to replace the converter. Just pull the tranny back and replace it.

 

[Will]

Why isn't your mechanic doing basic troubleshooting? He's just guessing, and listening to your friends advice and that guessing could kick you in the wallet pretty hard. ANd there is no guarentee that a rebuild (which is usually dump out the good parts and put in new parts) will fix it.

It's not the torque converter. That things works the same either forward or backward. The thing that could go bad, the one-way clutch in it, is used in every transmission position. If you want to test the torque converter, mash the throttle to the floor with your foot hard on the brake. You can check almost every clutch and band in the tranny for holding power by doing this in every gear position and seeing if the tach goes past about 3000-3500rpm. If it does, it indicates a certain something is slipping. If the converter one-way clutch is bad, it will have a low stall speed in every gear--like 2000 or something. Something in there is slipping and you need to get it to repeat the problem.

This is from my old manual, and I knoew they applied some secret tricks to get another gear out of the old 4-speed A4LD but going from what I see, the only two things that are applied in first gear (no matter the lever position) are the overdrive clutch and the forward clutch. The overdrive clutch is applied in reverse as well so if you can't get it to slip in the reverse test--it ain't that.

The forward clutch is applied in everything but reverse. Or it was on the 4-speed version. So trying the stall test in manual second should fail the stall test if the forward clutch is bad.

If that stuff is all good, and the long reverse is still causing it to slip, then I suspect something to do with the fluid being sucked up by the tranny and not being available for use for a moment when you put it back in drive. The low and reverse band is only applied in manual low and reverse. See if backing up slow and starting out in manual low will slip. If it doesn't slip, then i would suspect that servo is taking too long putting the fluid back maybe.

There are also control pressure checks that can be made. You screw a 250psi pressure gauge into a plugged hole behind where the shift shaft goes (or went) you can test the control pressure of the internal circuits and check for system leakage. For instance, you found the stall test failed for the OD position--there could be only one of two things wrong--a one-way clutch--which is not a hydraulic device--or the forward clutch. If the control pressure is good with the leverl in the OD position then it is probably a failed over-running clutch. But it won't be that because that is holding in every gear except OD.

My entire speil is almost worthless because I have no idea how the all-electronic trannies operate--though I can guess. My guess would also be worthless. But this mechanic should not be guessing. If this were mine, I would have the factory service manual and be following the very simple troubleshooting steps outlined in it. It could very well be a clogged filter taking a moment to get the fluid going after being in reverse. Or even low tranny fluid. It's about $40 to pull it out, look around in the tranny pan and in the bottom of the tranny to see what you can see, and put it back together.

From your symptoms--you have 2 episodes, right? It works right all the time except the glitches. I wouldn't panic and start writing checks just yet. Troubleshoot.

 

[rboyer]

I just can't believe that the mechanic didn't troubleshoot further. I think that Will prettymuch summed it all up, he should have recommended a filter/fluid change since it is cheap and also considered regular maintenance and if that didn't work he could have tried the stall test and checked the line pressure in less time than some people spend on the toilet. You really need to have the thing properly diagnosed before even thinking about replacing the torque converter and/or transmission.

 

[Jspafford]

Flywheel? This is an automatic right?

Flexplate is more like it. It would not move it that came loose from the TC.

 

[Will]

That's not even a possibility. I tore one on a Mopar--they are a little hand-sized thing and the starter teeth are on the converter.

It sounded like two trains trying to use the same track in a narrow tunnel when it went.

I can't imagine tearing a full size flexplate. They don't have individual fingers sticking out like so many Dien Bien Phu's, and the bolt pattern is much larger to the holes at the converter are less loaded so I think they are much stronger.

 

[mrthuse]

Many Thanks

Lots to think about.

I tried to keep the original post as short as possible w/o sacrificing salient info. Here's an update:

Yep, all fluids were replaced about 2K miles ago. When the slippage problem persisted after replacing the speed sensor, my mechanic hoped it was something as simple as fluid not reaching where it should. He checked the level, and all was as it should be. We're satisfied it's not a fluid issue.

He suggested the "see a trannie specialist" route and sent me to his guy about 4 miles away. Saw him this morning.

The trannie specialist agrees w/ much of what's been posted here, but also agrees w/ Brett S. that regardless of what could be causing the difficulty, considering the mileage, the only was to get it right is to drop the unit, inspect it, rebuild and/or replace outright what he determines is the cause of the problem and reinstall the unit.

I trust this call since my original guy's never steered me wrong - when he can't do well what needs to be done, he sends me to other guys he knows whose work he respects. I've never found his advice off the mark, and I posted here to see what my options might be w/o pulling the trigger perhaps prematurely.

After talking it over w/ the trannie guy, we're waiting until the summer's a little longer in the tooth (and I have a bit more $$$ to do the deed), and then he'll take it on a Friday and return it on Monday. He estimates the job between $1.5K and $1.8K. He assures me that as long as I don't beat it to death by slamming it into gear when it slips, I can wait a bit to do the deed.

Interesting side bar: He also hinted that the '99s had problems w/ some trannie's overheating and certain bits glazing as a result. He asked if I'd ever had overheating issues. Since I hadn't (knock on wood), he said he'd look the unit over, and if he found anything that looked like it was getting cooked, he'd offer a fix of a separate bypass from the radiator to cool it all down - plug up the current feed from the block and replace it w/ a new one independent of the engine.

Since I'm leaning toward having the trannie rebuilt, anybody wish to chime in on the replacement cooling line?

P.S. You guys are the best. Am new to this forum and you've made me feel welcome. Thanks.

 

[Bent Bolt]

A trouble code would be nice to have. A speed sensor will NOT cause a trans slip.

Anyway, these trannys have a problem blowing out valve body gaskets resulting in low line pressure. Most commonly the symptom is a flare on the 2-3 and/or 3-4 shift but I have seen no reverse, no forward or manual 1st only. Installing a pressure gauge will find it. These trannys need 110 psi in drive.

There is a service kit available which is a new separator plate with bonded gaskets and a EPC blow off valve. I recommend to have a competent trans shop to install it as the valve body needs to come off and a few parts removed/installed.

 

[mrthuse]

Update, folks:

Am bringing the Ranger in for a transmission inspection and possible rebuild tomorrow. I'm printing out these comments and sending them along w/ the truck. We'll see what happens.

And many thanks for taking the time to respond and for offering advice before I pull the trigger. I'll post results when I have them.

 

[mrthuse]

Final Disposition:

Well, I pulled the trigger and went for the overhaul. A few hours after dropping of the Ranger, the trans guy called and said I definitely had transmission issues. I reiterated the go-ahead to do the repair. Four days later I picked her up.

Here's the inventory of repairs: replaced torque converter, reverse band, all clutches and steels, all gaskets and seal, all bushings and rings, rear ring GR Brg (Hub-> Case), filter, pan gasket, and 10 qts. of fluid. $1800.

Gear shift is stiff, but the automatic seems to be doing what it should now. The job's good for 12 mos. or 12k.

Opinions?