I have an 81 xj12 he. Not working in d. Moving in 1 & 2 and reverse but not on a slope. Oil and filter changed. Still not solved. Is there an adjustment band in these gear boxes? Or am I looking at disc and gearbox issues?
Hi Shane, the transmission is the common TH400. Has bands as far as i know and you can find a lot about that on the forum, certainly, or on the internet. There’s also a failure chart in the shop manual and someone might be able too look that up for you. I can check tomorrow if you want…
David
Thanks for the reply. I’d appreciate if you had a look. This is my first vintage model so any help or suggestions are welcome. Thank you
I can send you a pdf scan of the workshop manual that has everything about the 400 including failure charts and so on if you message me your email address (click on my user name and you should be able to send it to me in private). Anyways, said workshop manual is worth its weight in gold if you want to maintain and diagnose that car. I’m glad to have it, and this forum of course.
David
I can’t seem to message you David. Could you message me and I’ll reply.
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No external adjustments are listed in the Jaguar manual, Shane - except for the selector linkage…
As far as I can see; the selector linkage adjustment just ensures that the gear lever detent for the gear selected, matches the detent for the selector arm at the gearbox - which controls the internals’ shifting within the box. In principle, that slightly moving the gear lever will move the selector arm to a different position - which may or may not make a difference. However, with a slightly different reaction to ‘D’, ‘1’ and ‘2’ linkage adjustment check should not be omitted…?
‘Slipping’ means that the engine revs up but car not moving…right? I assume that you can ‘feel’ the box engages when ‘D’ selected - some drop in rpm, and possible ‘jerk’? Any difference in ‘1’ or ‘2’ engagement? One thing for sure; if the box is slipping, engine reving up with no motion - it is not advisable to go on beating that horse. Slipping will cause very rapid wear of the band and clutch linings - which will require extensive repairs.
The cause for slipping may be worn linings, simple wear, but also by incorrect pressures due to too high or low fluid levels, internal leaks - or a fault in the valve body…to mention the obvious.
I assume that correct procedure were used in checking fluid level after changing? Idling the engine for several minutes to warm up the transmission fluid (since you obviously cannot warm it up by driving) - then move the gear lever slowly through all gears and back to ‘P’. Then immediately check the level with the engine idling…?
Incidentally; did you notice anything unusual in the drained off fluid, colour, debris or smells…?
Frank
xj6 85 Sov Europe (UK/NZ)
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Only just bought car. It seemed to drive home without a problem. Then when I took it out again it started acting up. Not driving in d. 1 and 2 it moves but not as it should. Brought to mechanic. He changed oil and filter. He said oil was dirty and filter wasn’t fitted correctly. Sorted these issues but problem still occurs. If I’m looking at big money to sort this I’ll be bringing it back.
Presuming that you have enough fluid in it, correct dipstick, checked while running…
Check the operation of the shifter linkage first. See if the positions of the cabin lever correspond to correct positions on the trans shifter.
There is a vacuum modulator that plugs into the right side that could be bad.
This is a very common trans so any trans shop should be familiar with it.
Plenty of them on the used parts market if you need one.
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With fluid clean and level correct, Shane - the only thing externally adjustable is the shift linkage. It is essential that this is carried out first - it costs nothing, anything else likely will…
Basically, during drive-off the same internal components are used irrespective of gear lever position - that there is a difference in box behaviour in ‘D’ or ‘1’, ‘2’ selected, may relate to shift linkage. But it is essential that you confirm if the box is slipping - or misbehaves in other ways…
Slipping means pressure is not fully applied to bands or clutches - or worn band/clutch linings, in the latter case; driving will aggravate the situation. If reverse works normally, slipping in forward only, points to the forward clutch malfunction. However, that is only an assumption - requiring deeper investigation…
The main diagnostic tool is oil pressure tests, initially confirming that adequate pressure is available and properly regulated. Further on road testing may indicate source problem - but repairs will require strip-down. Loss of oil pressure might be caused by a failed seal - which in some cases may be accessed remedied through removal of the oil pan and filter with out gearbox removal. However, whether such a leak may affect only forward gears is uncertain…
A possible source of trouble is malfunction of the valve body, which controls how pressure is directed to bands and clutches in the proper sequence during shifting. The valve body can be separately removed with the box in the car - and can be replaced or disassembled and inspected/cleaned. While replacement is fairly straight forward, overhauling the valve body requires care and some competence - only nominally a DIY operation…
If there is no change with shift lever adjustments; the problem may cost money…
Frank
xj6 85 Sov Europe (UK/NZ)
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