OK, I've read a fair amount on the topic, I still can't decide..

1997 Disco 1, truck has 188,800 miles, it runs and drives surprisingly well.

I'm 85% through all the neglected maintenance and fluids, which brings me to the transmission.


The transmission shifts well, always a solid shift, no slip, torque converter locks up right at 53 MPH

The fluid is reddish / brown, I know it could use changing but I've read enough warnings (not many actual examples) about changing fluid in the high mileage boxes to be paranoid...


Thoughts?

 

I've done drain, filter, fill's on LR's without any issues. It's the full blown flushes that get ya into trouble.

 

According to GM's own tranny rebuild publication I once red, they tackled that question and recommended, one is always better off (in terms of longevity) replacing the fluid, even on old tranny's that may not have had their fluids changed. I've done it on some vehicles I've bought that had really dark fluid. Never personally had a problem. I wondered about the same thing as you and heard all sorts of opinions that really mostly anticdotal that went something like, "a guy I knew " or "..my uncle once had a truck that..." kind of statements without any other facts of the situation. Maybe the guy's uncle towed a 10k lb skid steer up a mountain on a hot day in a truck with 180,000 mi on it? Who knows?? Some ATF's, if you look at the bottles, have anti-shudder and additive packages in them for older, high-mileage vehicles. That's what I would look for. For example Penzoil I know has it.

I think where this comes from are people and mechanics who have high-mileage cars with weak tranny's, probably having problems, and they take them in or change the fluid in hopes that doing so will 'fix' their problem, and then ultimately the trans continues to degrade or dies sometime soon afterwards, not due to the fluid but just wear or abuse (abuse can include not changing the fluid in the FIRST place).

The key thing to bear in mind as I look at it is Dextron III can only hold a certain amount of particles in suspension by design, after that, they're going to start to clog the filter/increase wear. The darker it is, the more stuff that's in there. Yours probably has a lot of particles from normal friction clutch wear and so on. The other part of the job is you also get to replace the filter which allows freer flow and less work for the pump (since the fluid is generally 'drawn' into the pump). ZF transmissions are robust units anyway.

Well, that's my take. Do as you feel right. Hope it helps...

 

For anyone wondering, I changed out 4 Qts of transmission fluid with O'Reillys High Mileage ATF, also a half bottle of Lucas transmission conditioner

Have put 200 miles on the truck since, no lack of performance, even seems to shift smoother but that is likely my imagination


I plan to do another drain / fill after the FLRC Fall Rally - then tackle the filter replacement by end of the year.

 

Rule of thumb for me on high mileage is always drain and replace = ok. Flush = kiss of death. Just my 2c

 

x2 on the flush! even just draining and adding the conditioner [like you did] and new fluid really goes along way. I did the same as you on mine,i looked closely at the drained fluid and there really weren't any signs of crap [like metal shavings]. i'll probably change filter next time too. just don't go above 30k miles before a change

 

When you guys say flush - do you mean the type done at a transmission shop (or DIY setup using the output / input lines for the trans cooler?


Regardless - I won't be doing either, just making sure I understand

 

yes,stay away from doing that,i mean just drain and refill,no machine using pressure to force fluid thru all parts of tranny,in other words no hook-ups!

 

DON'T Power Flush the AT at a shop! Power flush = Problems.

Just run the truck around the block for 10 - 15 minutes to get the At fluid hot, pull the drain plug and drain the fluid. That's all you need to do. If you feel real ambitious (it's involved), then replace the At Filter too. One tip spray #10 (there are 6) and #9 in the pic with penetrating oil first. The clamps (#10) get very brittle and they crack, but you can get them from AB > (4) corner RTC5733 > Auto Transmission Pan Clamp-Corner 4 Required (Genuine Part # RTC5733 ) - Land Rover bolts\clamps\brackets\washers from Atlantic British AND (2) Straight/Center > Auto Transmission Pan Clamp Straight 2 Required (Genuine Part # RTC5734 ) - Land Rover bolts\clamps\brackets\washers from Atlantic British

 

exactly.