TCM Calculated Torque Request
 

Hello, I recently found myself a 2004 XJ8. I fixed the intake manifold seals to solve a lean condition causing restricted performance. I have good trims now! However it would also have a gearbox fault on the 5-6 gear shift. I drained and refilled the transmission fluid. Still no better. I reset adaptations and now it throws the gearbox fault at the 3-4 shift. Today I replaced solenoids, valve body seals and pan. Still have bad at 3-4 shift. While I was looking at live data for the TCM I noticed 2 things. First voltage at the TCM was going to 15-15.1V. That seems a bit high to me. Second calculated torque request stayed at 0 and never changed. That seems like something to investigate. I know the MAFS has something to do with this. But I was wondering if it is the only sensor involved. Also where do I start checking for wiring issues? I can see MAFS in live data and it seems to be fine. I would really appreciate some thoughts here. Thanks!

While browsing I learned that the alternator goes to 15.3 after start up. That would explain that.

Rick,

All 20 year old 6HP-26 transmissions are unhappy in a different way, but they are all unhappy. Lots of people on the forum (including me) have tried every form of refurbishment short of a total rebuild and very few of them have succeeded. After replacing fluid, seals, solenoids, a full valve body rebuild, resetting adaptations, and enduring a year of misbehavior ,I finally took it in for a $4000 full rebuild which you can see being done here: The gearbox has performed flawlessly for 25k miles since the rebuild.

In my opinion, once these start acting up the way to minimize your suffering is to take it to the best transmission guy you can find and pay him whatever it takes.

Good Luck
Jeff

P.S My symptoms included flairing into neutral on 2-3 under hard acceleration, flairing on downshifts, refusal to downshift at all, TCM CAN Bus codes, refusal to go into reverse, clunking when coming to a stop and a few others I have forgotten. As you will see when he tears down the transmission there was no obvious smoking gun, EVERYTHING was a little worn and causing different symptoms under different conditions.

How did you drain and fill the transmission?
It's not real easy? If not done properly with measuring the fluid temperature you won't have the correct fluid level.
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Yeah I get this. It is for sure tired at 160k. I'm just trying to make a little better. A rebuild might be an option. I saw some kits that weren't terribly priced.

To the fill hole at 40c. Followed tsb procedure.

Great as that must be followed.
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stator support bushing is smoked

before the 06 model year these things have terrible trans programming and they wear way faster.

you can drive around the problem for a really long time if you get a feel for when it’s gonna flare and throw a gearbox fault.

Yeah I figured out I can make it shift smooth by accelerating then letting off at the shift point. It had some strange electrical problems today. Bright lights wouldn't turn on, then lights wouldn't turn back on after turning them off and on, dome lights wouldn't work. Turned the car off and back on and it all worked again. It's obviously got multiple problems. I got it pretty cheap so I'm going to tinker around and decide if I want to rebuild it. Maybe there is something electrical making it worse. I can hope any way lol.

113 K here. Had not been neglected, and I had the drain/flush/new filter-pan/ refill, etc. done in the 90 K range.

But still...t is getting a tad cranky now and then..

"Plan A" is to acquire a used-but-hopefully-lower-mileage trans, learn to rebuild it meself w/o having the vehicle deadlined during the process.

Makes more sense, my case as both the 2005 XJ8-L and 2011 L320 use the same ZF. I think. But even if only near-as-dammit / not 100% identical, any special tools should transfer, and the learning-curve conveys.

Encouragement? You could just acquire yerself a SECOND X350, even a third?.... and the hire-done vs learn-how & DIY choice becomes easier?
:)

I cannot honestly recommend the L320 for training, even for casual amusement.
Not unless you have ready access to Anti-Tank rounds and a safe place for frustration-plinking?

Your E Clutch is smoked based on the 5-6 and now infamous 3-4 shift issues.

Only solution is either a rebuild or swap another trans in.

I too would rather learn to do it myself than pay someone thousands to do it for me. It doesn't even look that difficult. The clutch kits aren't that expensive. Dropping and reinstalling in my dirt driveway however is what I'm worried about.That sounds like it will be a fight. I don't know about finding another one. I haven't seen a cheap one yet. I have 2 cars and can be down one for a bit.

THIS.

The design is so radically different from Dynaflow, Powerglide, Dual-range Hydramatic, Powerflight, Torqueflight, etc. all 'fluidics' controlled uber precision and uber-UBER sensitive to particulates, burrs, scars, etc. accordingly.

ZF's were designed from the outset to be repairable, as it also meant lower-cost to assemble.

DOWNSIDE?

The assembly was designed to be done by machines. 'Robots' IOW that have a(ny) special tools, jigs, or fixtures needed for their particular sub-specialty built-in .....to their own 'hands' and 'arms'.

Page Two:

The six, eight, ..and more... speed/range units have a highly common design philosophy.

Learn one, all others - while not identical - are close enough to be easy to learn more rapidly than average.

T'was never 'fun', but a half sheet of plywood and a bag or so of sand or crusher dust can sort that so far as stable enough for a tranny jack & such.

No need to "pave' enough to park a whole pimpmobile on the flat & level.

"Cheap" is a relative term! More especially where your own labour is/can be/ might NOT be.. a factor.

Look, rather, at opportunity cost comparisons. Temper with "probabilty".. of seeing to completion, vs abandoning half way, for example.