5HP24 Operation & Torque Converter Design info

[civdiv99]

Every couple of weeks I get around to reading some of the posts here. Seems of late there's been discussion about transmission shuddering and similar issues.

A couple of months ago I uploaded a long post with discussion and pictures after I disassembled my 5HP24 and repaired (I won't go so far as to say what I did was a "rebuild") a problem. In my case, a bad bearing allowing axial play allowing fluid pressure issues allowing the "A" clutch to slip, etc. etc.

I've seen some discussion lately regarding the torque converters and possible shuddering caused by the lockup feature slipping/shuddering/whatever. Not attempting to solve anyone's specific issues here, but I did a lot of reading and scrounging around for docs giving theories of operation, power flow diagrams, and such before I began work. (For anyone that remembers my Nov post, the trans is still brilliant in operation).

On thing I found very interesting is that the converter in the 5HP24 is default status in the lockup position. Let me rephrase that - the transmission unlocks the converter with fluid pressure, not the other way around. I uploaded a couple of pages from a BMW transmission operation manual. I got an eye opener when I reinstalled my transmission after teardown and parts replacement. I had drained everything, so although I could fill the pan to the plug level, as most of us know then you start it up and finish the job, temperature specific, etc. When I first started the car, foot on the brake (it was not up on jack stands), it lurched a little, shuddered, and the engine died. I knew the converter was already in lockup from my reading, but I didn't really expect that. Started it up again, a little shudder, and then smooth as fluid pressurized and filled passages.

My point is this - the fluid used to unlock the converter and control it's gradual locking and unlocking during operation travels in passages in the 2 splined shafts (yes, 2 shafts, plus the tangs that drive the fluid pump) that engage inside the converter. My specific problem was a result of a bearing failure - but it was clear to me by all the sealing rings and so forth that I replaced on the various shafts that wear or other issues can certainly affect fluid pressures in a completely different physical location. So, for example, if the converter lockup is screwing up, but the computer and pressure solenoids are doing their job, replacing the converter may not necessarily be the answer. I have no idea if there's a way to test pressures in various parts of the system, but I will say there are a lot of blind plugs in the case which I suspect are there to be able to read pressures along various routes. The ZF rebuild manual I bought has a lot of scoop, but does not discuss this particular aspect. Nevertheless, for general info it's food for thought in deciding what may be going on with a particular trans operation.

[RRPhil]

As I mentioned here : http://www.xoutpost.com/801192-post39.html the 5HP24 is very unusual in not having a torsional vibration damper for the LUC (to save weight and space) and so a continuous slip mode is employed instead at lower engine & vehicle speeds. In the Range Rover (same transmission and very similar engine) the LUC is never fully locked below 56mph so the torque converter can spend a lot of its life in this continuous slip mode. I expect it's very similar for E53.





I hope you don’t mind me correcting your statement that the LUC’s default status is in the lockup position. The default is to have pressure/flow directed to the front of the LUC piston by the converter pressure valve which holds the converter open. It has to be designed this way so that if the transmission has to go into limp-home - say through failure of the electronics - the LUC stays open to allow the vehicle to pull away from rest (& then stay) in 4th gear. To activate the LUC, pressure from solenoid 4 moves the converter pressure valve so that it vents the front of the clutch piston to tank and at the same time moves the LUC shift valve causing the rear of the converter to be pressurised, holding the LUC locked. This can be seen clearly in the hydraulic circuit.





So basically the two valves work together to reverse the direction of flow through the converter. It either flows in through the turbine shaft and out through the stator shaft (LUC off - default) or in through the stator shaft (no flow, just pressure) with the turbine shaft earthed to tank (LUC on).

Phil

[civdiv99]

Excellent info, and no, I don't mind at all. Clearly the little piece in the document I had did not tell the complete story. Wish I'd have had that hydraulic diagram when I had the valve body and everything apart. I'd probably have spent an extra evening checking stuff out.

Civdiv99

[SkidmarkX5]

Greetings civdiv99!

Well, your prophecy has born out. It did indeed go South in a hurry.

I neeed to order a shop repair manual and then all the other stuff.

Could I trouble you for the source of your parts?

Thanks,

SVS

[wallyx5]

I ended up using these guys. There is some parts info there and they were very helpful by phone. MZF-Bayer Transmissions Hope that helps.

[cgwebb]

I have a 2003 4.6is , I am also experiencing the vibration (over 4000 rpm and under load) my question is : was the vibration on your car under load ?? also in 1st Gear I am getting a whining noise ( almost sounds like a loud super charger!)
I cant wait to get this puppy up on a ramp and tear down the Tranny

[TiAgX5]

Originally Posted by cgwebb

I have a 2003 4.6is , I am also experiencing the vibration (over 4000 rpm and under load) my question is : was the vibration on your car under load ?? also in 1st Gear I am getting a whining noise ( almost sounds like a loud super charger!)
I cant wait to get this puppy up on a ramp and tear down the Tranny

Mileage? Have you checked the fluid level? This trans is known to "howl" when underfilled.

[mgbmwx5]

ZF Transmission parts: The CTSC - ZF Parts

[SAR]

I'm in process of rebuilding a 5HP24 to repair a defective A drum on a 98 with 145 K miles. The tranny has been on the bench for a couple of weeks now and the new parts arrived yesterday, so re-assembly starts over the next few days.

While reading up on the job, I've found this post and others about the torque converter and vibration which has me wondering if mine has a problem as well. I've had an annoying vibration for several years now that I've never been able to identify and have done all the usual things to try to remedy (balancing, new tires, replaced wheel bearings, bushings, etc but have never had it go away. All seals are good on the rear end and visually the prop shaft & couplings look fine.

The vibration comes on between 50 and 55 mph and often smooths out as speed gets to 70+ mph. Occasionally it is apparent at lower speeds, usually 30-35 mph. Travelling the same road (I live on Vancouver Island so we really only have 1 highway) the severity can vary day to day - some days worse than others, but never more than an annoyance, so road surface doesn't seem to be a contributing factor. Since starting around 2002, it progressed slowly for a few months, but hasn't gotten any worse for the last several years.

Until the A drum failed a few weeks back, I've had no symptoms from the tranny that caused concern beyond the occasional abrupt downshift or delay in upshifting from 2->3. However, where I live is hilly, so most of this I've attributed to the effect of the slope. There is no vibration or noise from the transmission at any speed & I have replaced fluid (using the part fill method) twice over the past 6 years using Esso fluid &, both times found nothing wrong with the fluid coming out or any shavings / debris on the magnets.

In a roundabout way, this brings me to my question - reading this info, especially the table showing the speed where lockup occurs, makes me wonder if I have a problem with the torque converter, perhaps a bad lockup clutch, that is causing the vibration. However, as I've had no other symptoms & it seems to have stabilized at the current state, rather than cntinue to deteriorate which I would have thought was a more normal failure pattern, I'm not in a rush to throw another $500 at it on spec (which is what it seems a TC delivered would cost me).

Appreciate any input or thoughts that I can use to help finalise my decision and plans for re-assembly

Scott

[cgwebb]

I have a 4.6 is , it has the classic harsh 2 -1 downshift, reading this post, if the engine RPM is too low surley the torque converter could not be disengaging due to low pressure due to low engine rpm I have looked EVerYWHERE on dis to increase the engine rpm and cant seem to find it despite certain posts.