transmission oil is black

'98 Pontiac Montana. We have owned this from new and have been extremely pleased with it.My wife has been driving it and complaining about a little surging down the interstate. Check engine oil pops up every once in awhile. We've taken it to the dealer, and 2 other garages around in the area.

All these people have said different things. One has sprayed water on the engine and it jumped. We've had a technician drive with us hooked into the computer and he says the transmission is slipping slightly but the engine seems good. It idles a little rough. The spark plugs have been changed. Another garage has said they weren't put in well and he changed them and also the wires.

The engine I swear is good except the idle is just a little rough. I drove it the other day down the interstate. I noticed what at first was a surging. I looked at the tach and the engine was increasing in RPM's every time the engine "surged". My wife then tells me "oh the oil is black in the transmission" Oh well, thanks for telling me hon! That's a bad thing!

We take it to the transmission specialist, he takes it for a test drive. Comes back and says it's definitely slipping. Give him a few days to look into some other things, bring it back Monday. Which is today. I just got off the phone and apparently I was talking to another guy. he says it's the engine surging! OMG can anyone give me a straight answer? I told him the tranny oil was black. "It is?" He says the cost to do a complete rebuild would be $1500.

I have heard that there can be a shock to the system with oil that bad and being replaced. Is this true? Shouldn't we just have the oil changed first to see if that helps? I know there is something gone in the transmission but maybe? Just maybe?

Please tell me I don't have to go through the process of a rebuild.

Thanks for your response.

what were the codes the the PCM stored? Have you checked the trans fluid is it dark but full?

How many miles on the van? Have you ever had the tranny serviced? I would try changing the fluid and filter first.
Regards, HC2000:)

If the engine is surging, i would check for vacuum leaks. Check all of the vacuum hoses for holes/leaks and use WD40 around the intake gasket edges.

Thanks, I forgot all the nice important info.

It has 140K on it and no fluid changes. I know thats not good maintenance.:banghead:

The fluid is black. We told the guy just to change the oil for now. My wife says it seems just a tad better.

When I drove it what I saw was the tachometer surging up, but we would be going slower. I would be almost positive the "surging" would be deceptive and that the transmission is slipping enough that the engine rpm would rise.

Then another assumption would be that because of the slipping of the two surfaces inside of the transmission would be creating fine particles thus making the oil black.

My overall assumption is that there is something wrong with the torque converter engaging. With my very limited knowledge of anything automotive, it wouldn't surprise me to be off on this assumption.

The code testing was done awhile back, the guy said there was a little slippage, but I have no idea what the codes were.

...The fluid is black. We told the guy just to change the oil for now. My wife says it seems just a tad better.....the slipping of the two surfaces inside of the transmission would be creating fine particles thus making the oil black....My overall assumption is that there is something wrong with the torque converter engaging....

Slippage can be coming from more than one area inside the transmission, including the lockup in the torque converter.

There will be foreign matter related to clutches or bands slipping, but the main culprit is HEAT caused by the slippage...the oil literally cooks and turns black like in a fry pan turned on high.

You are riding a time bomb that will likely disintegrate at some point. Re-build time can't be too far away. It will stop working altogether one day, leaving someone stranded, (probably leaving your wife stranded and mad as heck!)

Lucky for me we have AAA. She's been driving it like this for 3½ years she says LOL. Up until lately, we seriously thought it was something with the engine.

We are going to keep an eye on the oil color and change it again in like 5k miles. We know the majority of the oil is left in there so hopefully the oil will gradually get better without a flush to it.

As for the slippage, we are just going to bear it for a little while longer until we get money to have someone really look at it.

Thanks for your responses everyone.

Did you have the codes read? I'd do that . If you had the codes read, please write them down here (not their meanng as reported by third parties, just the number). Autozone read them for free. And possesing a code reader is not an expense, it is an investment.
Dark transmission fluid is indeed not the best ofthings. But as slipping is concerned, I'd like it to be understood a little more: when TOrque COnverter Clutch is engaged, slip is normally zero: but as soon as you depress the throttle a little fast or if significantly more than normal cruise torque is asked for, computer will release TCC (because it is a very small clutch just good enough for cruise torque) and you will have normal torque converter slip, and engine will gain several hundred RPM, and this is NORMAL, or normal "surging" if you want , not "oh my god" SURGING (whatever one wants that to mean....or wants to sell)
If TCC IS engaged and slips because it lacks oil pressure or/and cluth material is burnt, then that is a problem and this will generate a code: thatis why I would want to see the codes. Slip can also occur at any of the several clutches in the transmission...and such a condition would indeed burn the clutches and cause debris that turn the fluid to black....But speculation is just that..until it is verified. SO as suggested, replacing the tarnsmission fluid and filter is a good move, but it seems you did not have a full flush, so will be difficult to appreciate any subsequent color change..
If it turns out only the TCC clutch is shot....then you can have it disconnected and live like that...forever, but there is a slight fuel penalty at HIGHWAY speed, not in city driving because below 50mph TCC does not engage anyway, and the CEL will be ON all the time. It depends if you feel that is worth 1500$, but that is your car, and you must see for how many more years you will stick with it.
Now a badly slipping transmission (at the main clutches level) will slip more and more at an alarming and increasing rate; if it has done "that" for years....then I question the diagnostic.

thanks for the very informative response. you were right, no flush. someone told us to be careful of a flush so we opted to keep it going for now with just a fluid change.

I called the shop where we had the guy with the computer hookup and they didn't store any codes. I was right there in the vehicle and all he really said was there was some slippage going on, but not much. It's all very vague I know.

I'm sure we'll find out one day what it is when it breaks down. What else can we do. No one here has been able to definitively give us the straight shot answer and I honestly think there could be many scenarios, thus the many types of answers we have received.

I'll look into a code reader.