Hard to exactly title this one. I have a '97 Disco 1 automatic that when driving will abruptly downshift 3-5 seconds after an upshift. Its usually between 2-3 gear. It shifts normally otherwise and once in 4th stays in 4th. Transmission fluid has been changed and filled to the correct level. When I changed the oil the crazy thing was the oil on transmission dipstick looked nice and red. When I drained it its anything but. I have a new filter set to put in but I'm hesitant to do so if my clutch packs are roasted and it needs a rebuild anyways. The crazy thing is when in gear it doesn't "slip" in terms of power, not that I can tell at least - it just eases into the previous gear if driving normally or abruptly if you have your foot in it. It has 200k on it so I'm sure I'm due for an overhaul on it I'm just wondering if there are other things that could be causing this such as electrical gremlins (which this car has on occasion - checking all the ground points is on my todo list) or other external to the transmission things that could also be a culprit.

Thanks!

 

Ensure the fluid level is proper, that's the key first step. Look in the manual and follow directions.

Other things which can affect shifting are sensors not operating properly, like throttle position sensor, bad body/engine/ecm grounds, mis-adjusted cable (or a bad cracked plastic grommet/bushing where it hooks to the tranny), speed sensor, bad brake switch possibly?? Is the temperature of the engine accurate to what it should be operating at? (per the temperature sensor)? Does the temp sensor read ambient air temperature properly when the vehicle is 'cold'? That could 'fake out' a tranny. Put a scan tool on yer rig and look at all those things to verify and shoot the upper radiator hose by the engine with an IR temp gun to verify the temp when warm. If the engine is operating at 140*F when warm, for instance, that is too cold, can cause shift issues potentially. I believe there is also a temp switch for the trans up by the radiator (trans cooler), make sure the trans temp is in the correct range. I would also inspect/clean the throttle bore for any deposits esp around the throttle blade. Even a little deposits can goof up normal idle/operating. Rule out any engine vacuum leaks. Ensure there aren't any other major codes. I would unhook transmission electrical connections and inspect them and the wires that come out off them, for corrosion. And also any wire burns or breaks. It could be as simple as a poor electrical wire connection at the tranny.

Check all those things, which are pretty easy to do ....and rule that they are all 'good' FIRST, b/c often its the common little things. Then, after all that, if it still shift's funny, I'd look into the shift solenoids in the transmission and research that. If you have a good scan tool, you might be able to manually engage them ...or at least see what they are doing when the problem occurs. Or have a tranny shop do it. If a trans shop says "It's junk" w/o showing you what's going on in detail ...with specific scanner data ...beware and, leave. Have another trans shop (or two) look at it. Trans shops are always looking for work and be your own self-advocate so you don't get ripped-off. Dig around Y/T and Google about shift solenoids on these tranny's. They might be easy to replace on your own. Many older tranny's were. But for sure check all of those other common engine/ground/electrical/vacuum/mis-adjusted shift linkage ...issues first before you jump to solenoids.

I haven't had to change solenoids in a Disco ZF, but on our Jeep Grand Cherokee (Mopar Tranny), it ran & shifted terribly when we first got it (used) 14 yrs ago. A lot of deferred maintenance. Needed a TPS, throttle bore cleaning. EGR pipes were cracked/shot - those needed replacing. A couple leaking vacuum hoses, ...and engine grounds were not put on the engine properly. Once those were addressed it ran beautifully, and shifted 'better' but still shifted oddly and would float in/out of OD. I had the dealer replace a shift solenoid (I was super-busy with work at that time). But on that tranny it's a do-able DIY job for a good mechanic. Charged me $350 to have the dealer do it, so that was a bargain for me at that time. Took a few days for the transmission to 're-learn' but then it has shifted perfect since. That was 150k miles ago. Now it has 255k miles on it and still runs/shifts great. If it ends up being a transmission shift solenoid you can probably change that or see what a shop would charge. Watch some Y/T videos on it. I'm going by the book and other general tranny issues ...not any real-life issues on my L/R's transmission. But those are typical things which can cause bad shifting, and I googled issues with 97's.

So... have a look at some of those things I listed and you should have a clearer idea of what is "good". And check out the possibility of the electrical connections and solenoids if all else looks good. Probably other forum members here will have some other helpful ideas. Just b/c it has 200k doesn't mean it's worn out. Doesn't mean it's not either. The ZF's are a pretty good transmission.

Let us know what you find.

 

My '96 will buck sometimes (downshift/upshift/downshift) right near lock-up around 50 MPH. Was much worse when I just bought it over 10 years ago, now only occasionally (after an ATF drain/fill). Usually reducing throttle gets it to calm down.

Decided to try a 3x drain/fill with Valvoline Maxlife ATF, plus a bottle of Lubegard Platinum for the final fill. Should have the results in a month or so.

 

from the owners manual, page 105 (108 in the pdf)

"AUTOMATIC GEARBOX FLUID LEVEL CHECK & TOP-UP

The automatic gearbox fluid must ONLY be checked when the engine and gearbox are COLD (see ’Note’ below).

Ensure the vehicle is resting on level ground, then select ’P’ (park) and start the engine. With the engine running at idle speed and both foot brake and parking brake applied, move the selector lever to position ’1’ and then back to position ’P’.
With the engine running, withdraw the dipstick from the filler tube and wipe the blade clean. Reinsert the dipstick fully and withdraw again to check the level. Top-up to maintain the level between the UPPER and LOWER markings on the dipstick, with a fluid meeting the minimum specification defined in ’General data’.

NOTE: In extreme ambient temperatures, the level of fluid showing on the dipstick will vary. To ensure an accurate reading, the level should be checked at an ambient temperature of 68° F (20° C).

DO NOT OVERFILL!"


https://drive.google.com/file/d/0Byt...xjq9MLRGCI_flw

 

Hmmm.... You're right Walt! I forgot about that land rover unique tranny fluid service. (face plant). Been a while. Thanks for the reminder (I scrubbed my first post so I don't run anyone astray).

The lube guard isn't a bad idea but I would do the other checks too I listed if problems persist.

 

The Disco 1 trans is entirely mechanical - there are no external electrical sensors that will directly affect it's changing. It all comes down to pressures and fluid viscosity (to an extent, as it varies with temperature).

The kickdown cable needs to be adjusted correctly and the shifter cable... other than that, it has to be an internal issue as there are no other external inputs.

If you have the correct fluid and it's at the correct level, there has to be an issue causing incorrect pressures that trigger a kickdown or shift.