Transmission fluid change on old transmission good or bad idea?

I recently purchaced a 5spd 99 SR5. It has a bit over 219,000 miles on it and has been running (Almost) fine since I bought it. It sometimes hesitates shifting into 3rd and doesn't always want to get into reverse. I want to replace all of the fluids so I can start with an accurate baseline as to when they were last replaced. This being said I am a bit unsure about replacing transmission fluid. (or rather gear oil in my case) I checked the fluid level today by removing the fill plug on the trans case. The fluid is brown in color but still transparent and smells kinda funny. I have heard conflicting things about brown smelly fluid. Some people say to replace it and others say that the particulate is what's making the transmission run. Being as though the transmission hasn't been replaced and is working mostly ok I don't want to do any damage. What do you think? Is it ok to change the transmission fluid or should I not and hope for the best?
Thanks,
Alan

 

why not drain half and mix in half new fluid? you get to keep some of the particulates and have some new fluids too? makes sense to me but im sure someone will call me out on this. good look on gettings your answer OP

 

You say "gear oil in my case" and "removing the fill plug on the trans case". So you have a standard and not an automatic, right?

If it is a standard, then you can drain and refill with the specified fluid in your manual. You already pulled the fill plug, so you know it will come out. Just drain and refill.

If it is an auto, then just drain the pan and refill. This way you only change some of the fluid. Do this enough times (some do it with oil changes) and your fluid is refreshed, but you didn't shock the trans.

Try using search and you will find threads on changing standards (manuals) and automatics.

 

I guess I forgot to mention that it IS a manual.

 

change it

the myth is autos go bad after a change of the fluid

 

change it, I would say even change it in an auto.

 

Do it...

 

+1

Autos go bad after a change when they are improperly "power flushed"... the process shoves things into places it was never intended to be.

A proper, complete "flush" would consist of disconnecting the trans cooler, running the engine with the trans being cycled through the gears, capturing the fluid exiting the trans, and replacing it with new fluid being added to the other side of the break in the line.

The transmission itself drives the fluid replacement, and cycling through the gears completely flushes the valve body.

I would have this done on a trans with over 100k that has never been serviced. If you are in SoCal, the only guy I trust to work on my trans is Mike Loverich at Inglewood Transmission in Fullerton, CA (shop used to be near LAX, thus the name).


On a trans that has been serviced regularly, all that is required is to simply drain and refill the pan... about 4-5 quarts.

 

on a 2012 auto, with light towing and some mountain driving, how often would you recommend simply draining and refilling the pan? would you replace the filter and drop the pan everytime also? if not how often? Perpetually performing this service theoretically should never require a complete flush if done often, correct?

 

You say (OP) that it smells funny.
Have you smelled fresh gear oil?
That will smell funny as well.
Having said that, I would still change it out.

 

This! Definitely change it. Don't power flush it, just flush as described. Clean fluid is always a good idea!....

 

Really? Why flush it at all if you're going to leave some bad with the good! The purpose of a flush is just that, to flush out the contaminants.

I don't buy into the idea of a power flush on a high mileage tranny as some of that crud actually does some good by taking up the tolerances between rotating parts and to remove them may create an unfavorable result. But I do like the idea of a "drain and fill."

After the 1st drain and fill, drive your vehicle and get the fluid up to operating temp and then drain and fill a 2nd time. I've gone so far as to do this a 3rd time before I felt comfortable, but you do what you have to do. And yes, it can get pricey but worth the effort.

 

It's good practice to "baseline" any 100-150K+ mileaged used vehicle that you purchase. That means replacing all fluids and high service filters. It puts your mind at ease as far as a start point to watch things. Windshield washer fluid? sure,,who's to say the previous owner didn't water down the funky colored stuff that is in there,,, as the freezing point outside rushes into the low doubles.

Yup, I do brake and clutch fluid as well every 2-3 years.. If you don't have a pressure bleeder,,find a shop that does and get quotes.

If your auto trans has lived it's life on a regular power flush during service intervals,,then good for you. If it hasn't,,then let it be or just do as described above, flush only with trans fluid changes back to back.

Dino gear oil turns to semi-heavy black molasses when it fails. And it stinks waaay worse than cooked auto fluid. you'll know immediately when it does. Lots of mileage can be put on gear oil, compared to auto fluid.. I went 60K before swapping them all out,,but I was/am the 1 owner.

 

Not a myth with 1st gen autos, the A340F is a good trans but is fussy about maintenance, do a drain & fill, no flushing unless done correctly & 2nd gens sealed no access transmissions are supposed to be a complete flush IIRC...

This...

 

A buddy rebuilds twin pin Harley's and Honda's. He's pumping engine oil in one side and out the other on first startup. He puts 5 gallons thru them as they sit there and idle. Flushing all possible contaminants and grit right out, ring seat metals, lubriplate type greases, bits and specks, ect.

Same principal and end result basically, but the only way to be absolutely sure.

Sales dude was trying to talk me into a auto in 99. Glad I passed.

 

Change it,
add this
http://www.marlincrawler.com/hardware-tools/hardware/low-profile-magnetic-drain-plug

drive it untill your next oil change, drain it again, check for chunks of metal.

If none replace the fluid with redline MTL Gl4, and throw in
http://www.marlincrawler.com/transmission/shifter-parts/heavy-duty-shift-lever-ball-seats

you will be good to go.

oh yea also bleed and change the clutch master fluid while your at it.
helps

 

Yeah but see the difference is you don't wait for oil to heat up & expand like trans fluid does, plus ATF is 100% detergent, i dunno, what I DO know is that I've had automatics in the past that i never so much as checked the trans fluid & never had an issue . These are touchy as hell, but yeah I almost did the conversion to a standard when looking at $3400.00 for a complete rebuild, ended up with a great used one for about a $1000...

 

Your conversion would have been cheaper,,once shopped around.

But understandable with the $1000 find, and it bolts right in place.

$3400. Holy Shit. Probably depends on who was on the rebuild table that day.