How long do you suggest warming the trans. up for before flushing it?

 

Enough to get it to at least 120F. That time varies a lot with ambient temperature and driving cycle.

 

Did I mention I am a big fan of cardboard? This is not a mod I would do without at least filter changes and perhaps a shift kit or valve body mod.

 

Actually, I did connect it to the REAR cooler line (return line from the cooler) and I still got the mess. I also had the tranny warmed up, but it was only 110, not the 120 that Mark recommended. Anyone have any input on when I should have seen air in the clear hose that I attached to the return cooler line? I never saw any after 4-5 quarts, yet I could hear the truck start groaning while switching gears, making me a little bit nervous. Also, is that normal during this procedure? I'd be happy to do it again if I could figure out what caused the leak.
Still curious as to what happened, but I do recommend a supplies list for that write-up includes a gravel driveway or a lot of cardboard!!

 

I never switched gears myself. at first. I just ran it for a few minutes and checked the fluid. Topped off and kept going until the fluid was the same as what I was putting in. Then I went through the gears on a drive cycle.

 

If you go through the gears while flushing you change the fluid that's inside the clutches, too. If you do it on a drive cycle you just move the old fluid in the clutches into the pan with the new fluid.

Brian, you might have a partially plugged cooler or restricted line. That would cause the bypass to open and fluid to come out of the other line. It could also be a leaking/stuck bypass valve.

To test for a restriction, get two buckets and LOTS of cardboard! Disconnect like you are going to flush it. Aim both lines into the first bucket and start the engine. Once there is a solid flow out of the return line from the cooler move only that line into the second bucket for EXACTLY 15 second, then put it back in the first bucket and shut the engine off. If there is at least one quart in the second bucket there is enough cooler flow. If not, something is wrong.

 

I had the same problem you did with no air. I probably came up a few quarts short too because it sounded like the tranny was working a little harder. Did it a couple of times until I reached my comfort level. I'm sure there's a few quarts of old fluid still churning around in there. My tranny was much colder than yours but I was doing both diffs at the same time and they were drained so I couldn't warm it up (was working all 3 at the same time but wasn't going fast enough to flush a warm tranny like I had planned). I second the cardboard (or a lot of kitty litter). I changed the pan gasket, filter and put in a Factory Tech valve body while I was under there.

When I get some time I'll probably drain and fill on the pan and put some fresh Mobil 1 in there to thin out what's left of the old stuff mixed in.

Next time I dive in for a fluid change I'll try Mike's test to see if my slush box is clogged too.

BTW does anybody know how much fluid I can expect to drain if I just drain the pan (it's a 4x4 pan) on the 4R100? I would like to get enough tranny fluid without overbuying by too much (Mobil 1 syn Mercon V is not cheap). I know you can return the unused quarts but keeping the price down keeps the wife (and me) happy.

Thanks. I hope that answers your question and sorry for the hijack...

 

Just dropping the pan should require 5-8 quarts. It varies.

And who is this Mike, and what's his test?

 

My bad. I was on a teleconference call while I was typing (ssshhhh, don't tell anybody I was FTE'ing at work). One of the guys' names is Mike and I just ran with it. The memory loss and attention deficit (knows as "shiny object syndrome") is starting to kick in as I get older. I apologize.

 

subscribing....... soon to do this change

 

I allways thought that atf was a detergent,and if your tranny hasnt been serviced regurely.and if u flush your tranny or change your fluid that it will break stuff loose and make your tranny slip.

 

It should take ~7.5 quarts, if you get it hot and steadily recheck the level.
At least it did on my fathers's '02 4x4.

 

It isn't a detergent, but it does have some detergent in it, just like motor oil does.

 

Nah, I don't think so. I think that comes from folks who don't take care of their trannys, then it starts showing problems, so they change the fluid. But it already has been damaged due to lack of maintenance. Does it then make sense to blame clean fluid for the certain failure looming on the horizon?

I actually have an example of that. My wife had an 89 Chevy Astro. The PO towed with it, and I had no idea if the 700R4 was maintained. At the 110k mark, I changed the fluid. We put ~20k on it before I changed it, so I figured it was time, if not late. At ~120k, I put in a new tranny. Does that mean the fluid caused the failure?? Some folks think so, I guess.

 

I have 148,000 on Nyx and I'm assuming the stock transmission. Any reason I should not switch to synthetic? I'm about due for a tranny flush & filter change. IIRC doesn't Brian (of BTS) recommend it for a new/rebuilt tranny but not a high mileage one?