Flushing th 475 transmission

[Eyez Open]

I'm about to change the tranny oil. Since that is going to happen I can't help but think about flushing the entire system. So the question would be can this be done using the cooling lines? Could one decouple the lines, dumping the output into a empty bucket and the return line being placed in a fresh gallon of fluid?

I know the tranny will have to be in gear while doing this..What I do not know is..is this just a hair brained ideal? W%

[eXodus]

Yes you can use the cooling lines - but be aware - there is lots of pressure on them. So secure them in your buckets and wear safety googles.

even when doing that - you are not going to get all old fluid flushed out without using gallons of new tranny fluid.

I'm cheap,  I'm just opening the drain plug on the tranny or drop the pan - let it drop out for a few hours (for whatever reason after an hour of being open - it dumps another quart)

Measure whatever came out - Then refill it with the same amount.  Drive around for a tank of gas - repeat.
Do that every 30.000k miles or 3 years, whatever is first.
Got various hard working vehicles to well over 200k miles with that method and perfectly shifting transmissions.

[Eyez Open]

Thank you for your reply, this RV sat for 10yrs. Removing all the old fluids is a high priority for me, so far so good no seals are bad...Removing any possible containments would be the goal,time will tell of course. The engine and tranny are high cost replacement items dropping a few hundred there is worth the risk/cost benefit for me

[eXodus]

Get some big heavy buckets and a helper to turn the engine on and stay at the key.

It is going to go through a gallon of fluid in no time.

https://www.youtube.com/watch?v=7-t0_-tXb34

[Eyez Open]

Get some big heavy buckets and a helper to turn the engine on and stay at the key.

It is going to go through a gallon of fluid in no time.

https://www.youtube.com/watch?v=7-t0_-tXb34

That could not have been said any better. The tranny dumped 1 gallon in 15 seconds. No big splashing the dump was in a 5 gallon bucket. As of now I'm back to the store for more oil, I've been dumping 1 gallon and then a 1 gallon refill. So 3 gallons out two gallons in and the fluid is still deep cherry brown. From this point I will drop the pan and change the filter. I will keep up this exchange up to 4gallons  or clear fluid running from the tranny cooler line. 

[eXodus]

That's even faster then I remembered   My guess was like 30 seconds for a gallon, but apparently those old tyranny's are even better in pumping.


When I do my drain and fill, I usually get about 4-5 quarts when just opening the plug.   Usually latest after 3 gallons the fluid is close to what I put in so that I call it a day.

1. Drain and refill (1 gallon)
2. Drive a tank
3. Drain and refill (1 gallon)
4. Drive a tank
5. Drain and refill (1 gallon)
6. Drive a tank
Clear.

My theory is - that the new fluid mixes with the old one and the fresh detergents within have more time acting and neutralizing the debris inside the tranny.
That's my justification to being lazy and only changing the transmission filter every 100.000 miles.

[Eyez Open]

Well I've encountered quite a annoying speed bump. GM in there infinite wisdom placed a cross member support in such a manner one cannot access just one of the pan bolts. Either I notch the cross member or lift the tranny high enough to gain some type of access. Lifting the tranny can have some serious implications or major work. Actually I've had more than a few speed bumps...I've ordered a bunch of curtains...maybe hanging curtains are a needed distraction.

[eXodus]

which end of the tranny? tail end? 

I had to lift my transmission when the tranny mount disintegrated and collapsed and I had to change it. 
I learned - that you need to unbolt that mount first, before you lift he tranny - since it will not allow you to lift it far enough to get that mount out.

You can lift it quite a bit without hitting anything.

Notching the crossmember seems reasonable to a certain extend, it's well overbuild. You got a picture of the bolt and member?

I just had notched my A/C compressor bracket to get to a bolt of the intake    I took a drill and a metal grinding bit

[Eyez Open]

Pics you say? That is quite easy, don't let the pic fool you. A small 1/2" open end barely makes it, the box end not going to get there. And a pic of the mount bolts, my worst fear there would be realignment issues and bunged up threads.

So we're you able to raise the tranny two inches?

[eXodus]

That's a tough spot to get a wrench in.

can not remember how far it the transmission had to be lifted but it was quite a bit


You see that screw - on the mount. Yours might have two of those bolts - mine is the newer version and has only one. The tranny had to get up that far to get the mount out.  It's at least 2 inches. 

I mean you can unbolt from the transmission or the crossmember. If you are not trusting the crossmember bolts - unscrew from the tranny - there is not that much play in the mount that you have to worry about alignment.  When you are already on it - change it

Make sure you got the RV secured with blocks and the parking brake on - otherwise there is a lot of tension on that mount.

[Eyez Open]

Ended lifting the tranny about two inches, and yes the tranny shifted to the point where some heavy maneuvering will occur. It did take a 1/4 inch drive, 4"extension and a swivel to get it out however..Getting it back in will be much easier. Below is a picture of the filter top, it looks like it was filtering a mud creek. I will be placing two pan magnets in a attempt to contain as much sludge as possible..
X
Things worked out quite well I believe, tomorrow will be all telling. Dropping 1 gallon then adding a gallon, twice I did that. Then I pushed out the third gallon and dropped the pan. Maybe 8 ounces was in the pan very easy to finish a filter swap. Added a third gallon and stopped there, tomorrow is another day.

Another approach...permanent fix. Oh to be young again

https://youtu.be/giWMU-CPqOA

[Oz]

Fingers crossed!

[Eyez Open]

The system worked out fine, it ended up using 3 1/2 gallons or *14 quarts. Now on to dropping the propane tank, it is a monster...6' long and about 18" inches wide. I cannot find any info on this tank as to weight but a WAG puts it at about 120 lbs. Bombs away 

I should add the rear lower transmission mount is quite easy to unbolt. Doing that makes it very easy to align that stud you see above back into the lower mount again. lifting the tranny did cause a shift of about 1/4" one loosens the rear mount and the stud drops right in with no thread damage. Exodus posted the upper mount bolted to the tranny, there is another bolted to the cross member. Putting that small bolt back with the difficult location is another story....it would be very easy to cross thread that little darling. I used a old method used in the shop many yrs ago to get it in with no damage. We would use old rubber vacumm hose, attach the hose to the tip of a spark plug and use that to turn spark plugs into hard to reach plug holes, you cant strip threads doing that and hose is very flexible extension. Oddly enough with just a minute or two of  fumbling around with method the plugs/bolts always start right..it has never failed me.

*Factory service manuals state *11 quarts total capacity for the TH 475 transmission, it appears i am bit long on fluid here. If so draining out the excess will occur from the cooler lines.

[yellowrecve]

An ordinary floor jack will work. The type with wheels. It helps to have a second person to balance the tank on the jack.