98 4WD Strange Tranny problems...

[LAN2UNOW]

98 4WD LT, was running fine for a long time and then recently it just started rev'ing up and not fully engaging into a gear. It would do it, but you had to ramp up the RPM's until you could feel it slip into whatever gear.

Never lost a gear yet, bought it used and determined it was possible at 130K no one ever touched the tranny before. At the point we took it in, it barely moved and had major issues shifting between gears and going into reverse. When in a gear it's totally fine, but like shifting from 1-2 and up you'd have to rev it up or allow it to rev down in order to get the shift to complete. Obviously when it was time to shift back down it'd go reasonably easy but at speeds where it wants to shift back up you get the up/down gear selection problem because it's not shifting smoothly.

Again, no gears have gone 'out' and it's going on in all the gears including reverse. Had the tranny filter/fluid changed (very ugly black water) even though the dipstick didn't show anything that bad. Led us to believe it was a clogged port or something somewhere? After that flush n fill - AOK! Worked like a champ for at least a week. Then you'd feel it have slight shifting issues here and there between gears but reverse was fine.

Drove it home the other night - next morning - nada. It'll go into gears but not without rev'ing to apply the pressure and then you can feel it 'slip' into the selected gear and actually move. Obviously that's not going to work so it's time to determine what's really wrong since flushing the gunk didn't work UNLESS more gunk broke loose and re-jammed the filter or something?

Totally stumped at this point, there's info all over the Net about TCC solenoids, possibly vaccum switch/solenoids, modulators and more but they conflict like mad. Some folks say no more vaccum, then I find statements 2000+ models still have them? And parts places are worse. Found links to the various parts mentioned and they give little clues as to what's supposed to be in there.

I'm not a fan of climbing under there without any clues, it can't be the vehicle speed sensor because the speedometer's just fine with no wavering or otherwise. We did have a Check Engine Soon light pop a couple times, but then that goes away after more driving (same trip) so it was considered false reports because it's not readable later on.

Anyone have any clues on this? Gotta keep this thing on the road so anything would help!

Dave

[MT-2500]

Black burnt transmission fluid is from fried burn clutches.
What all was in the old filter and bottom of oil pan.
You might get a few more mile by changing the filter again and dropping in a bottle of Lucas transmission additive.
But It is about gone.
Time for a rebuild ot another transmission.
MT

[LAN2UNOW]

Oh com'on... DOA? Even i'm not buying that at this point without further proof...

As I mentioned what came out was 130K old as far as anyone can tell, so it's more used beyond reason than indications of burnt anything. Not to mention the fact what's in there now for a few weeks since the last change is 100% perfect. No discoloration or anything else. The tech that changed it all is older than probably both of us put toegether and I know his experience level very well. If he'd have seen anything looking like a toasted tranny, I'd have heard about it. He spent some serious time doing the procedure, far more than normal, because I asked him what the deal could be the first time. He had nothing to lose or gain by giving me good or bad news about it's condition.

The tranny pan and filter just had fluid, he said it was nearly clear in there and the magnet had nothing to speak of for the age of the tranny/vehicle. So no warnng signs of fatigue or failures there either. Thus why this seams more like a lack of proper pressure to engage the converter during the shifts than anything else. As I mentioned, when it's in a gear there's plenty of power without over-rev. Just at shift points it's having the issue.

It's sounding more like a failing TCC the more research I do but that's inside and beyond my scope of DIY capabilities.

[MT-2500]

If the fluid was very ugly black water as in your first post it is caused by fried clutches.

As said you might check or change filter again and get a few more miles out of it.
But your transmission is fried.
If you want to check it out.
More power to you.
Put a transmission capable scanner and a pressure gauge on it and see what they say about it.
Watch the amount of slippage is each gear and the shift errow and shift adptive data readings also pressure solenoid reading.
Also get codes and post back code no.
Ps
If your tech is older than me he is sure enough a old fellow.
I been doing transmissions 45 years.
Good Luck
MT

[LAN2UNOW]

LOL, well ya it's time for a second opinion simply because that's not gear I carry around to perform those tests and what he mentioned didn't indicate that what he took out was related to failures like that.

He's up there, in the high 70's for sure and has had repair/fuel places in the past, you'd have to see his present shop to understand the history and skill. that's why I don't question the results he mentioned as not being totally DOA and time for a rebuild or total replacement.

Sadly where it's located isn't near the one tranny shop I'd swear by so the locals here will get a crack at it and if they say it's that severe then that's what we go with. But it just seems strange that a failure like that would occur so suddenly without any warnings, fluid leakage, shifting problems prior to the start of this or anything else to cause it. Least not that I'm aware of anything that was done to it in the last 25K miles for sure and the way this is failing now doesn't seem like prior to that point either.

Not doubting your experience at all, just that if there was a plausible explanation for this happening it'd make more sense.

[MT-2500]

Good luck and let us know how it goes.
MT

[blazes9395]

I defiently doesn't sound to good at this point. i agree with MT, you need to get a scanner on it and see what is going on. If you don't have access to a scanner, you need to at least get a pressure guage on the transmission.

The 4L60e that you have in your '98 is ALL electronic, there are not vacuum lines/connections etc, etc. Its electronic. IF its throwing a code, you need to see what it is. Again, a good scanner would retrieve that code from the PCM's memory, even if the SES light is not on on your dashboard. If it still has gears, but its softly going into gears, first of all if you want to try and save the tranny, stop driving it. Driving it like that will burn it up in no time.

At this point I am surprise your not seeing the P1870. At any point have you ever had hard shifting, especially from 1-2, a bang shift? Is your TCC locking up still?Soft shifts indicate line pressure problem, which can be a few things at tis point. A guage reading at this point would help. With a 130k on it and poor/ to no tranny servicing, I'd say the odds are against you at this point.

[LAN2UNOW]

Ok, she's been parked not going to risk burning that out completely at this point. Heading to the shop tomorrow, so we'll have any better news. The initial diagnosis over the phone (obviously) is that there could be a clogged flow port preventing proper fluid flow but opening it up and finding out what, where and why it's blocked would be the key. Didn't say it wasn't totally gone, but did say it could simply be the lack of proper maintenance in the past that the gunk in there has kicked loose and the filter change didn't get it all. So now more gunk that wasn't totally flushed out may be loose and causing the problem once more since the fluid color hasn't changed to dark right away - which would match MT's dire diagnosis if it had changed within a couple weeks.

I had multiple folks recommend the Lucas stuff, even this tech said it needs a flush and examination more than just a drain and filter job, so we'll know more in 24-48 hours!

The codes are mysteriously clearing and he said it may be because while it takes a couple of trips to get that fault code, it then clears out when AOK reports come in from the days following when the problem didn't exist anymore. Rare, but it may have dropped off the memory map essentially. He has what's needed to ty to pull the codes out of it, so we'll see if it's in there or not! LOL