Well, after Superblue has been sitting in a parking lot for over a month now (yes, I have moved her around every week or so to keep her from getting towed off) I finally called yet another transmission shop that was recommended to me, out of frustration.
The gentleman that owns the shop I called had a general auto. service that specialized in transmission work for many years, but now it turns out he only does trans. rebuild work. He really seems to know his stuff on the subject. He listened patiently as I explained the symptoms and etc. I had been experiencing. The first thing is he corrected me in that I thought the 4.0s, like my '94 coupe, had ZF trannies in them. He says they have GMs. This is just the opposite of what I had always thought (i.e. that it was the 6.0s that had GMs). He is very familiar with that particular model of GM tranny.
His opinion, in short, is that I actually have an electrical issue, and need to locate a reputable shop that specializes in electrical system work. HIs thinking is as follows:
Apparently, vehicles with this model of GM tranny require at least a voltage of 13.6 volts in their system at all times. If the voltage falls below that level the tranny receives an error code in its computer memory somehow. Once it receives three such codes in short order the transmission pump system (?) tries to compensate and/or reacts by pumping harder than it should to increase pressure in the system. This extra-high pressure results in the very hard shifting symptom (i.e. 1-2 gears) and actually causes the memory circuit board in the transmission to perhaps overheat The trranny warning light illuminates sometime during this process. Turning the ignition key off then clears the code(s) in the trannyās computer memory (usually) and hence everything is back to normal when the car is restarted. If the circuit board is overheated, then this problem may not resolve until the board has cooled down a bit.
I admit this theory does seem to have some merit to it, based on the way things are when the issue arises. I was thinking though that I donāt have any other symptoms of low voltage in my system (ie.g. no warning light or dim lighting), although Iāve noted that sometime my voltage meter is reading straight up (i.e. 12 volts) while driving, esp. at night when everything is activated.
I have a Transmission ECU from my 94, 4.0 coupe parts car.
Even though the body was totaled it drove great.
Better even than my 6.0.
If it interests you give me a call @ 650.455.1110
Not true. Your 6-banger has a ZF electronically controlled box and as we have discussed multiple times, you donāt need a rebuild, you need to find which input (sensor or wiring) messes things upā¦
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
8
So, this guy probably worked on one six-banger Jag before and it had the GM gearbox, so he presumed they were all like that. The fact that he apparently made this assumption rather than actually look at the car is a bit troubling.
Iām pretty sure attydallas3 is correct when he said the 6.0 (read V12) had the GM transmission.
That is not a six banger, though I donāt know which motor he has.
My XJS, 6.0 liter, V12 had the GM 4L80-E which only cost me $2200 to rebuild.
āhe corrected me in that I thought the 4.0s, like my '94 coupe, had ZF trannies in them. He says they have GMs. This is just the opposite of what I had always thought (i.e. that it was the 6.0s that had GMs).ā
Actually, he was (supposedly) double-checking the fitment with a book he had while I was talking to him on the phone. Good thing I didnāt take Superblue to him even if he would look at it, as it turns out he also told me a whopper about a good friend of mine whose family has owned a tranny shop here in town for like 40+ years. He claimed they had sold the shop a few years ago and that he had offered to buy it, but got outbid by someone else (selling price supposedly $3M+!). Then the new owner got the bad news when he applied for occupancy permits that with the pit car lifts there were some buried tanks under the building that, due to EPA laws, required he tear everything up and rebuild. In that I hadnāt talked to the friend in awhile, I immediately called her and she confirmed for me the guyās story was total hogwash. WTH? Sounds like the gent had a few screws loose, and weāre not talking in his transmissions ā¦ So, Iām totally discounting anything he told me that day ā¦
Wow, Bob - that first TSB might just be spot on with Superblue. The only thing is, sheās a '94 MY, not ā95 (are the trannies the same part #?). I wonder if this same issue came up with the 94ā MY, or is it possible a PO put in a '95 tranny in a r/r? Too bad the '94 MY didnāt have OBD II, so I canāt verify any code #s (and nobody around here has a working JDS PDU! ). As to the second TBS ā actually, the 3-4 shifts and IIRC, the shift to/from reverse are not affected by the issue - the very harsh shifting is limited to 1-2 gears (or, is the harsh 1-2 gears thing the car being in ālimp homeā mode?).
btw, Bob, as to TSB #1, what IS the part # of the updated TCM, if I decide to give that solution a try? Is that the LHE 2400AH 001 mentioned? I know when I r/red the TCM early on in the problem I used the same part # as with the original one. Hence, it could have had the same issue as the original one.
Well I guess I just answered my own question, by checking the Jaguar Classic parts site. The '94 MY and '95 MY TCM are different #s, so that wonāt fix things, unless the '94 TCMs also happened to have that same issue with them and Jag did not put out a TSB on the problem for that MY.
Latest update ā¦ I finally HAD to do something with Superblue, as she had been sitting in the shopping complexā big parking lot ever since before my original post, and has been red-stickered twice (I tried moving her once). Possibly the towing co. gent was a Jager or former Jager (or really liked the car) and gave me considerable leeway the first time w/o towing her off.
Both times I went to start SB up to move her the trans light and issue did not come up. Strange. However, the first time I went to move her I discovered that one of her rear tires was very low. Odd, in that I did not have any air leak problems at the time I parked her. I would have wondered if some interloper had let a bit of the air out, but the valve stem cap was still in place. Even weirder, when I went to pump the tire up it was like the pump kept running and running (eventually shutting down from overheating ?) and yet I could get no more than about 15 lbs. of air in her. I could not see or hear any leak, though, and she stayed at that pressure. When I came back the second time, I added a can of Slime emergency tire repair to the tire, and then tried to pump her up again, but she stopped at around 20 lbs. or so PSI. Oh well, I went with it anyway and drove her on home last night. No issues going home or going to the office today, and tire seems to be holding at 20 (she has Goodyear Eagles on her, btw, from the PO). However, my low WW light kept flickering on and off, so I stopped by WM and put in just one gallon of fluid. After i poured it in, I went to test things and, although the headlight washers worked O.K., the fluid would barely, weakly come out of the WW jets. When I tried it later again that day at the carwash, nothing, and not even a hum from the WW pump motor. (blown fuse?). GRRRRR. What other issues is she going to have soon???
Anyone want to buy a '94 coupe w. 80K miles CHEAP ?
Wow. Maybe itās a case of āJaguar heal thyselfā, as I have mysteriously had happen many times in the past with some of my other Jags w. issues that suddenly cropped up, but very oddly ever since I picked up Superblue from where she was parked and about to get towed off last week the tranny issue has not arisen a SINGLE time. This is over several days (some of which the outside temps were over 100 F., btw), driving day and night, and having gone many miles. btw, I have not done anything to her, either ā¦ WTH?
In that I hadnāt talked to the friend in awhile, I immediately called her and she confirmed for me the guyās story was total hogwash. WTH? 
Sounds like the gent had a few screws loose, and weāre not talking in his transmissions ā¦ 
So, Iām totally discounting anything he told me that day ā¦
). As to the second TBS ā actually, the 3-4 shifts and IIRC, the shift to/from reverse are not affected by the issue - the very harsh shifting is limited to 1-2 gears (or, is the harsh 1-2 gears thing the car being in ālimp homeā mode?). 
Possibly the towing co. gent was a Jager or former Jager (or really liked the car) and gave me considerable leeway the first time w/o towing her off. 
This is over several days (some of which the outside temps were over 100 F., btw), driving day and night, and having gone many miles. btw, I have not done anything to her, either ā¦ WTH?