2004 LR D2 with 195,000 miles.Engine rebuild with flanged sleeves, transmission fluid renewed about 30K miles ago.

Transmission started in the last week or so to exhibit unusual behavior.

When coasting in drive, the transmission seems to kick down to a gear (it is a four ratio tranny, right?), causing the engine to brake the beast more than usual.

When under load, it does 50mph at 1,750 rpm, getting good mileage (over 15mpg).

Just when not under load, i.e., coasting, it seems to have more drag on the engine than it used to (e.g., when letting oof gas at 55mph, revs go up from 2,000rpm to maybe 2,500 )

And if I flick the throttle a bit several times (sounds like it's being hard on the u-joints) I can sometimes get it into a lower resistance coast.

Thoughts on issue? failing torque converter, failing transmission, some electro or mechanical switch or circuit elsewhere that is causing this added downshift drag when I start coasting while at speed.

 

Usually that is an indication the front pump is not putting out enough volume for the modulator to tell the trans to shift gears. The typical failure of the HP22 (99-02) is a front pump seal failure that leaks fluid pressure and the front clutch fails. They beefed up that seal and the front clutch on the HP24, but it still sounds like you are bleeding pressure somewhere. Does it exhibit the symptoms only in one gear, or does it happen in all the gears?

 

Thanks for the diagnosis.

The torque converter not releasing (unlocking?) when coasting at speed only seems to happen in 4th gear, but I have only driven in economy mode, not automatic mode, so I will test it gear by gear next time I am out.

I may be just smart enough now to be dangerous, but I read the RAV section on the auto transmission, and it sounds like the lockup solenoid is not disengaging when the throttle position sensor is at idle -- or the solenoid is disengaging but the pump doesn't have enough pressure to disengage/unlock the torque converter.

Could it be that the front pump -- I assume that this pump pressurizes the torque converter, which is what is either locked or unlocked, right? -- needs more pressure to unlock 4th gear than 1-3?

And if the front pump was leaking, wouldn't the torque converter be slipping both when locked up and released. I am not seeing any indication of slippage in the relationship between speed and RPM: again, at 50mph, the rpms are 1750, which I recall is about right (or should it be 1500 at 50mph?). Is there an RPM-MPH chart somewhere so I can confirm I am not seeing slippage when the torque converter is locked up?

 

should I attempt the stall test as written up in the RAV? Will this indicate if the pump is leaking or otherwise going bad?

 

Trans can leak internally almost anywhere (clutch pistons, accumulators, solenoids, valve body, etc) and bleed pressure that affect clutch engagement and disengagement. Other things that can affect engagement and disengagement are the solenoids and valve body spools, as well as the TCU and sensors. The HP22 and 24 were damn near bulletproof by they time they made it in to Discos, having been used in BMW years before we got them. You see many more post on the BMW forums about problems than on ours. You can swap some things like the valve body and solenoids if diagnoses leads you in that direction, but if it is internal it is almost not worth the effort of rebuilding because they are so bulletproof they have very low value on the used market. Most of the guys who part out Discos have way more demand for body components, interior, and engines than transmissions. Much easier to just throw in a complete used transmission and driver another 100k than to troubleshoot and rebuild. That said, I have rebuilt a front pump on one and know several who have had bad torque converters (usually start slipping, not an unlocking fault). When you test the gear behavior also check sport mode as well as manual mode.

 

Thanks Extinct.

Can't complain about 200K miles out of an automatic transmission.

Going t=out today to junkyard for a rear sunroof cable assembly, I test the D2 on the way to see if I have the unlock issue at other speeds/gears and will report back -- and to scout the 3-4 donors they have for a tranny.

Does a new transmission mated into a different vehicle require any programming to the ECU or is it pure plug-and-play (determines whether I do it myself or not).

 

OK, tested vehicle in economy, sport and manual modes, and in all modes and for all gears, the lockup is apparently not disengaging when I take my foot off of the accelerator, as it stays locked with the engine acting as a brake until, it seems the RPMs get below 1,000 (though not sure really if the lockup is ever disengaging).

According to the RAV, the lockup should engage in 3rd and 4th above 45mph (which mean it should disengage below 45mph?). Gotta do my homework on automatic transmission 101, understand a little better how the torque converter works exactly.

All three shifts (1-->2, 2-->3, 3--4) in the three transmission modes are very smooth and the RPMs match pretty well with the speed of the vehicle (1,750RPM at 50mph, somewhere between 2,500 and 2,600RPM at 70mph), so there doesn't appear to be any slipping: is this the correct diagnosis?

The smooth shifting leads me to hypothesize that it might not be the fluid pressure (EAV says there is only one fluid pump, but someone above mentioned front pump, implying that there is also a rear pump, and maybe the front pump only supports the torque converter?), but rather that it is either the lockup mechanism itself in the torque converter or the lockup solenoid. What should I try next?

If it is solenoid, then I think I could drop the pan and valve block to perhaps test the solenoid for operation (does it take 12V, 5V or something else?). If it is the torque converter, then it seems like an awful lot of steps to drop the transmission (almost seems easier to light the engine?

What'ya think?

 

There is no rear pump on this transmission. The torque converter lockup is typically locked by applying fluid to a piston/clutch arrangement in the torque converter. You mention it is not disengaging correctly, did you notice is it engaging correctly? At the correct speed with a drop in engine rpm? If it engages correctly but does not disengage correctly, it could be caused by two things:

1. Something is leaking pressure in to the engagement circuit, preventing it from disengaging correctly.
2. Something in the disengagement control circuit is not working correctly. Spool valve sticking, solenoid sticking, or something else. I have not looked at the circuit, but the spool valve and solenoid should be accessible from the bottom of the truck. You might want to look at the wiring circuit for the lockup solenoid, it might be possible to troubleshoot that without disassembling anything. Do you have any scan tool?

 

Is the fluid level correct? What is the fluid condition? How does it look/smell? Has the filter been changed? I would NEVER do a 100% flush. Do a drain, replace the filter, then fill. Then drive it a while and you can do another drain/fill 500-1k later if the fluid you took out was nasty. I also use on higher mileage transmissions the Lucas Transmission Additive.

I know this sounds hard to believe but I've also seen HP22/HP24's act very odd & the customer brings it in & usually a tech will diagnose it as a bad transmission. Then when you actually drop it the flex plate just falls to millions of pieces and the actual transmission was fine. It felt like it was slipping, slamming into gears or awful random vibrations.

 

Extinct and Best 4x4, thanks for the responses.

Extinct, no scan tool beyond a OBD2 reader.

Best 4x4, I am pretty sure it isn't the flex plate as the only symptom that it exhibits is what I am interpreting as the non unlocking of the clutch when I am off the accelerator until the RPMs get way down, below 1,500 and maybe even below 1,000. The only problem is the engine acting as a brake when coasting, i.e., the lockup not disengaging, until the RPMs drop really, really low (not quite to idle but pretty close).

I was thinking maybe it could be the TPS -- I replaced that a while back (6-8 months ago) while throwing parts at a different problem (a badly stumbling engine: turned out it was the jumper/extension wires on my relocated coil packs building up resistance and were causing misfires).

I have the old TPS still, so will swap it back in and see what happens, so I can eliminate that as an issue.

My other theory relates to what Extinct is saying about a spool (not sure what this is) and/or the lockup MV solenoid being stuck open.

So here's my theory/logic:

The pump produces more pressure the faster it -- and the motor -- is spinning.

If the valve is stuck open, then the lockup clutch engages when the engine gets to a certain RPM -- and the fluid pressure with the valve(s) open gets to a point where it can engage the clutch against the impeller body.

When stepping off the accelerator, with the lockup clutch valve(s) still stuck open, i.e., not closing when it get a TPS signal that there is no throttle, then the clutch will stay engaged until the motor -- and the fluid pump -- drop below a certain RPM at which point where there is not enough system fluid pressure to keep the lockup clutch engaged thru the stuck open valves.

If this could be how the lockup clutch behaves when the clutch valve(s) are stuck open, then replacing the valves (solenoid valve is straightforward, don't know what the spool valve is, no reference to it in the RAV) could fix it.

Thoughts on this theory?

In the meantime, I am going to change the Dexron 3 in it with new fluid (per this forum, I am using the Walmart brand SuperTech Dex3 (Dexron 111 in the RAV) as I couldn't find any branded Dex3 anywhere. BTW, the RAV says the transmission holds 2.5 gallons (19.7 pints). Is that right? I don't remember changing that much fluid when I changed the filter 30-35K miles ago.