Transmission Service Question

[1qwkdsm]

Ok. So I just picked a 2002 Pontiac Montana 3.4L V6 FWD with just over a 100,000 miles on it for $500. It had a leaking lower intake manifold gasket which I have since repaired. I have been driving it for about 2 months now and it runs and drives like a dream. I am getting ready to do some fluid maintenance on it and would like some advice on servicing the transmission. Currently the transmission fluid is dark with some visible sediment on the dip stick. I have a buddy that works for a local lube shop and they have a T-Tech machine which I am welcome to use anytime. My plan was to first add a can of BG Transmission flush fluid and allow the vehicle to run for approx. 30 minutes. Then use the T-tech machine to completely flush out the fluid replacing with authentic GM Dexron VI fluid, not the watery garbage they offer in the lube shop. Finally I was going to drop the pan and change the gasket and filter replacing the lost fluid again and adding a bottle of lucas trans fix for good measure. I talked to a few mechanics and am getting mixed reviews/feelings on this proceedure. Some say I should change the filter first. Some say to not service the trans at all and just "run her to the ground". :/ Can anyone else add some input please. Currently the transmission works perfectly, no hard shifts, slips, etc. Any input would be greatly appreciated thanks.

[WrathOfSocrus]

Some say to not service the trans at all and just "run her to the ground".

The first time I was looking to change transmission fluid in a car about a decade ago, I had looked into getting a flush and heard similar things from a couple local transmission shops. They said things like old cars that haven't been regularly serviced will be ruined by a flush and if they have gone more than 75K without a fluid change that most of them never drive again.

After reading around online I eventually found some things that shed light on the subject. Old fluid is slippery. If u put a dot on your thumb and rub your fingers together u can feel how slippery the old worn out fluid is. Then do the same with fresh fluid. It is clean and your fingers can grip each other. I think there are a few trans shops that just change the fluid and gun it backing out of the garage. With the old fluid still clinging everywhere inside the trans, putting it under power right away will have it go from slip to grip and that's when things can go terribly bad.

Armed with that information I was confident I could do a fluid change on an old car with unknown mileage on the nasty dark fluid. I made sure to block the wheels properly and leave several feet around the car front and back and gently ran it through all the gears with the tire off the ground. I just slowly let the engine idle and get the tire moving, neutral and let it come to a stop, then reverse. Then back to drive and feather the gas till it goes through all the gears. You can also do it with the car on the ground and go very slowly up and down the street and baby it a bit til it has gone through the gears and gotten up to temp.

I remember a friend of mine getting a Jeep that was slipping a bit and he changed the fluid. He went around the block and it stopped slipping. He came to a stop sign and tried to burn out and grenaded the trans. Turned into a 12 hour tour trying to swap out the trans just to find out the output shaft changed so his transfer case wouldn't work and had to swap that over too.

I have done a dozen or so fluid changes for people now and never had any of them grenade on me. Only one started to go and that car was heavily abused with 200K on it. I'm not sure about doing the flush deal I don't have any experience with it but I have done just fine without it. When you have the pan off you want to clean off everything you can and remove the buildup on the inside of the pan. I have also had luck using transmission flush and slick 50 trans treatment on badly slipping transmissions with great success. I'll be honest I am no pro when it comes to transmissions but I have stuck by what works for me.

[1qwkdsm]

Great stories WrathofSocrus. I'm sort of missing the point though. Are you saying to go ahead and do the flush due to your past positive experiences? Can anyone else chime in here?

[WrathOfSocrus]

I'm sure different people will say different things but from my experience I have done fine just changing the filter and fluid. The idea is not to go out and beat on the transmission but to let all the new fluid work its way through the whole system. My method of doing that is to run it through the gears with the tire off the ground so it doesn't have the weight of the car behind it.

People who say to run it into the ground don't know what they are talking about. I have no experience with bringing it to a shop and doing a flush so I can't comment one way or the other on how it works, but in my experience it has been unnecessary.

[bob442]

I would not add any additives for flushing or for old transmissions, the things that fail on these trannys are epc solenoids and lip seals. I work at a large transmission shop, and we do flushes all the time, and the only time we have problems is when a thrid party puts in a additive. So doing a basic flush and puting in a regular transmission fluid, with say a fluid conversion additive is fine, basically a product that turns a plain transmission fluid into dex 3, but not many of you know WTH i'm talking about.

Any products that claim to fix slippage and other crap are just something that swells up seals and causes problems down the line. there is no need to use a cleaning agent in a transmission as trans fluid is basically a detergent. As you change all the old oil out, the new stuff cleans, and all the sedements settle to the bottom of the pan or the filter.

So do a flush and filter.

[torq455]

I like to refer to it as a fluid exchange, not a flush were an additive is used. Or a pan drop and filter change (service).

[Azrael]

Since it's running fine, a fluid and filter change should be safe. If the old fluid looks really questionable, it might be a good idea to do the next change at a shorter service interval (1/2 or less?).