Got a gear box fault & restricted performance light yesterday.
Symtoms are:
Clear all codes and it will reset P1722 when you select drive and press the gas.
Reverse works fine and pulls good.
Drive seems to rev and then kick hard, appears to be in a higher gear.

Fault tree say that low fluid could be a cause, but with it pulling so good in reverse and high gear/highway speed, I suspect low gear internal problems. Does this sound right?

Is the tranny toast? Any good aftermarket sources for a rebuilt transmission?

Anyone had similar problems that were non-fatal?

All advice apreciated.

 

Here's some food for thought. There are quite a few external factors that can cause the transmission control module to adopt "limp mode" and select fourth gear only. Usually a peripheral fault like this can be at least temporarily corrected, restarting the car or disconnecting the battery will often restore normal transmission operation for at least a short period.

When you consistantly get the transmission slip and default, that's pretty convincing evedence of an internal mechanical fault. You can check the fluid level, or drop the pan and look for debris and cooked fluid, and that is most likely what you will find.

I had a '99 XJ8 in last week which chafed through a transmission cooler pipe, and lost about 4 litres of fluid. Obviously the whole underside of the chassis was wet, and reverse would barely engage but the transmission would still take off somewhat normally in first gear. So I'm guessing that extremely low fluid level would result in a fault more obvious in reverse...and that is the reverse of what you are experiencing.

I told this customer that his transmission was likely damaged as a result of the low pressures, and he authorized me to fix the leak and off he went. The other time I repaired a similar fault, the customer's '98 XJ8 lost its transmission about a year later.

So he low fluid scenario is not likely in your case, and it also causes a noticable whine from the torque converter at idle. You could test or replace both of the transmission speed sensors, replacing them requires dropping the pan and you will probably see enough to convince you that it is a pointless exercise.

 

Wouldn't a bad sensor also throw an additional/different code?

Would pressing the sport mode button force a low gear takeoff?

 

Ok, cleared the P1722 code, disconnected the battery and cycled the key to erase any memory. reconnected and tried again... same symtoms, even tried sport mode switch engaged, with same result. Dropped the transmission pan. Didn't find any pieces, shiny metal flakes, or signs of any big failure. Fluid is dark golden color. What is the color of the factory fluid?

Which sensor would cause this? Output Shaft Speed (OSS) Sensor? or... Turbine Shaft Speed (TSS) Sensor?

I see a lot of hype that the CASTROL IMPORT MULTIVEHICLE AUTOMATIC TRANSMISSION FLUID will work in XK8s ( according to their data). Have you seen this used in Jags?

 

Without doing homework for you, I believe that the 1722 code is flagged as a response to radically different readings from both of the two speed sensors. That's what the TCM will see if the transmission is slipping: the turbine shaft sensor tells the ECM that the normal converter stall speed has been exceeded. If either of the two sensors is faulty (and they are identical), my understanding is that the 1722 is the only code you will see with a generic scanner.

So it's POSSIBLE that one of the two sensors is bad, I read of this happening once on Roadfly XJ8 but have not seen it for myself. If you have a diagram showing the pin outs at the transmission or the TCM, you could compare the resistance of the two sensors: they should be close to identical.

As for fluid, put in whatever you want. I only use the factory spec Esso fluid, since that is the only lubricant approved by Jaguar and ZF for the 5HP24.

 

will check resistance on both tomorrow and post results.

 

Both the OSS and the TSS ohm out at 333 ohms. I saw a few tiny metal slivers on the TSS. Cleaned both, can they ohm out OK and still not pulse due to magnetism issues? Is there a different test, should I change both?

 

Well, I still think the transmission is wasted, but if one of the sensors was open circuit at the TCM you could have had a bad sensor or a break in the internal harness. I'll see if I can find any other suggestions later tonight, but my suspicion is that changing both the sensors ($50. each) isn't going to get you anywhere. What did you use to retrieve fault codes, and is 1722 the only one you got?

 

hand held scanner. only got P1722 (and of course the pass code)

Hard to believe the tranny is toast with it being so clean inside... no metal pieces in the pan. The wife drove it several miles in restricted performance mode with it stuck in high gear (caught all lights green and ran a few stop signs) but it's clean inside.

 

now that I know the sensor resistance is 333 ohms, where would be the best place to pull a connector and chech the resistance of the internal and external harness (through the sensors and back)?

 

BTW, I pulled the sensors out of the tranny to ohm test them.

 

Well, I would have tested at the TCM or at least the connector on the trans, to make sure the circuit was complete (post #5).

 

yep, that would have been faster... but I wanted to look at the magnet tip (for debris or damage). I've got all the pan bolts out except for 4 to keep the pan on (for keeping out dust while I decide what parts are needed).

Guess a lot of BMWs have this same tranny. You mentioned a post on roadfly refering to a OSS sensor failure, was it a Jag or BMW?

 

It was an XJ8, I think it was throwing a different code but I haven't had a chance to look . I'm trying to make some money right now.

 

well... I checked the resistence at the TCM connectors and got the same resistance (333 ohms). Put it in neutral and turned the rear tires forward and verified the resistance changed during rotation (it did). I get a new filter and gasket friday, so I'm going to change the filter and swap the OSS & TSS sensors. Put it back together, fill up the fluid and test it. If the ODB code changes to a TSS fault, I'll know its the sensor. If I get the same fault, then its got to be a failure in the tranny core.

 

New fluid, new filter, wires good <5ohms, sensor 333 ohms & varies as wheels are rotated by hand, Reverse pulls hard, select drive and the gearbox fault sets and she's locked in 4th gear. She will drive anywhere in this condition. I hesitate to think mechanical failure, because I thought usually 1st & reverse are on the same clutch pack and drum (reverse using the planetary gears after the band holds the drum), does the ZF 5HP24 work that way? Anyone else seen this? Aamco put their scanner on it and thinks a solenoid may be sticking or the TCM is malfunctioning... Any ideas? Is there a trick to clearing the TCM?

 

You might want to check for additional fault codes at a dealer/ repair shop with WDS or IDS.

 

Will they pull codes that a hand held scanner or snap-on scanner won't pull? I've hooked some top of the line scanners to it. I followed the Alldata fault tree with all passes to the end (where is says contact Jaguar). Does the dealer have a proprietary scan tool that can read other TCM data?

BTW, I noticed that after P1722 sets, and you cycle the key without clearing the code, it sets a 2nd gear missmatch code because its in 4th on takeoff... but you don't get the 1500 rpm slam into 4th like you do when you erase the P1722 and cycle the key. I want to get to the bottom of this, but I really like to get to the root failure and cause.

I had a brake light out (with no lamp failure indicator) and traced it all the way to two cracked solder joints on the resistor bank of the lamp controller (an easy fix). I don't want to R&R the tranny without having "smoking gun" evidence of the root failure. I'm sure most folks are just like that, that how we all learn. but... Transmissions seem to have a sense of mystery (not to mention about a million internal parts).

 

What, I'm supposed to know what their scanner can't read?

 

I'm guessing the WDS / IDS will pull other codes not found in the standard OBDII library. It couldn't hurt... unless they want to charge $125 for a service fee. I would recommnend taking it in early, when not alot of activity in the service area, may catch him in a good mood and will scan real quick for you.