Montana transmissions

[bottomtech]

The Montana vans do not have a sun gear in the sense that raffhauf mentions. The problem sun reaction shell was in the 4L60E that comes in rear wheel drives.
You may have a pressure control solenoid going out, which would explain the hard shifts and whine. Best to check the computer for any codes relating to the trans.
If you let it go too long, the rest of the trans will be shot.

[airmech]

My Tranny does the same sometimes (1999 with 210K). The tranny has never been changed and I regularily tow a heavy trailer. When the hard shifting starts i have found that if I stop and put the van in park, and then shut off the van, wait about ten seconds and then start it up again, it usually solves the problem. I have been told by a tranny shop that there is a sensor that sometimes goes south and this is what causes the tranny to shift hard. The tranny apparently goes into a "fail safe mode" and all of the internal pressures are maximized. This is what causes the hard shifting (sometimes you can even hear the whine from the pump in the tranny). Shutting off the van resets the sensor. This has worked for me for three years with no repairs to the tranny at all.

[rajjhauf]

No more Pontiac Montana tranny or intake problems now, am the new owner of a 2005 Hyundia Santa Fe. Will see if this is a better move. Thanks for all your help in this forum.

[blazes9395]

I was reading the posts on here and could not help but post something myself. Changing your trans fluid and filter and doing a full flush will NOT harm the tranmission. Your manual also states general change intervals, for most driving even that is not enough. If you leave fluid in for too long, old fluid losses its lubricating properties and its heat transfer properties. This only really applies to regular convetional tranny fluid, not fully synthetic fluid. Synthetic fluid has different properties, lasts 10 times longer than convential fluid and is generally better. When clutches and band start slipping, you are creating heat and when the worn fluid cannot transfer the heat quickly the way it was designed to, you are raising the operating temperature of the transmission - killing the transmission. The old saying of keeping all the particles within the oil will help is plain false. If you want to keep fluid in longer, have a full flush with fully synthetic fluid, but be prepard to pay twice or three times the price for the fluid. It is generally accepted that for about every 10% decrease in transmission fluid temperature, you can almost double the life of your tranmission.

[jhong1226]

airmech,
did the mechanic told you what sensor was going bad? im guessing that it might be the MAP sensor. but my van does not give any SES light at all and i have scanned it for codes but would not yield any.

[gkindub]

rajjhauf, I realize you no longer own the Montana but I was curious to know why you did not press the dealer to pay for the tranny replacement etc. Their work is supposed to be warranted for 12 mths/12K mi and the tranny shop said it was their fault the tranny failed. In my opinion 50K miles is nothing unless you're doing lots of mountain driving or towing heavy loads.

[redly1]

someone please explain to me how the tranny shop's fluch machine works.

1) where do they attach in and out to get flow through

2) how the hell can they garantee there is no old residual fluid in the machine from the last flush they perfomed?

3) does the fluid backflow through the filter? Or normal flow?

4) how do they deal with different types of fluid?? (chrysler vs dexron)

Personally, I'd never take my vehicle somewhere to do a flush. I just don't trust the bastards enough to do it right, aside from the above questions.

If auto manufacturers want owners to keep the fluid fresh in the transmission, why do they make them so hard to service?? How about an external filter like engines? How about a drain plug?

my $0.02

[rubberman]

my van has started this hard shifting. it doesnt do it all the time. It shifts fine when first starting out but after the van gets warm then it starts but it will quit and start up later. Its kinda off and on thing. Maybe i will try a filter/fluid change too.

[blazes9395]

Originally Posted by redly1

someone please explain to me how the tranny shop's fluch machine works.

1) where do they attach in and out to get flow through

2) how the hell can they garantee there is no old residual fluid in the machine from the last flush they perfomed?

3) does the fluid backflow through the filter? Or normal flow?

4) how do they deal with different types of fluid?? (chrysler vs dexron)

Personally, I'd never take my vehicle somewhere to do a flush. I just don't trust the bastards enough to do it right, aside from the above questions.

If auto manufacturers want owners to keep the fluid fresh in the transmission, why do they make them so hard to service?? How about an external filter like engines? How about a drain plug?

my $0.02

1) they usually disconnect the two cooler lines one is connected to drain fluid out, the other is connected to take fresh fluid in.

2)The fluid going in will always be the new fluid, no residue in new fluid tank.

3)The fluid flows normally, the way it is intended to, no backflow.

4)They deal with this by either using the appropriate fluid, or by adding the necessary additive package to the fluid for the specific vehicle.

The last point you bring up is a very good set of questions, an external filter would be a great idea, some rebuilders do put a external filter connected in-line with the cooler lines. As for a drain plug...I still cannot believe they don't pure nonsense...I agree they should.

[blazes9395]

As for rubberman, or anyone having the hard upshift, get it looked at right away, your destroying your transmission. The extra pressure put on the clutches as shown by the hard shifts, will tear it up. If the problem goes away and comes back, especially if you stop shut it off, and start it again, is usually(not always) but usually an indication of a bad PCS (Pressure Control Solonoid). Don't keep driving it like this, or you will be in for a rebuild.

[rubberman]

hell i'll trade in the stupid van before i spend that amount of money on it.

[jerryuus]

Mine sometimes does the rough upshift thing. I find a spot to pull over, cut the engine off for about a minute, all is fine. There is a pressure valve that could cause it, but a friend of mine changed his valve, and it did not cure the problem.