I have a 1975 series 2 (4.2) fitted with a BW T65 tranmission.
Since I got the car it is slow to up-shift. Basically, it hangs on
to each gear until approx 3600RPM. I have adjusted the forward band
and the fluid level is correct and still no difference. The
downshift is working well but the slow upshift is driving me crazy.
Backing off the throttle slightly at 3000RPM makes little
difference to the change rpm.
While you most likely have an issue, Fergus - you’re too unspecific…
Point here is that the shifts relates to the pedal position; with full
throttle the box will hang on to the lower gear until rpms reaches
3000+. The gas pedal tells the box what the driver wants from the engine
- full throttle means power is wanted, only available at higher revs.
Light throttle means that the driver wants economy - and quick upshifts.
Just like the way a driver would shift on a manual box…
A valid test is to note shift points at light throttle; the box should
then shift seamlessly 1/2 at some 8 - 12 mph and 2/3 at some 13 - 19 mph
- give or tale a tad. If it doesn’t comply; something is definitely awry…
Daniel’s points are spot on; a sticky governor or a downshift cable
adjustment fault are the usual culprits. While some itsy bitsy trial and
error adjustments on the downshift cable may work for minor
discrepancies - the best idea is to set the downshift cable by pressure
readings. Any transmission shop can do this in a jiffy, or you can use a
pressure gauge for DIY ditto - if you are so inclined…
The point of this adjustment is that it may, apart from correct setting,
also reveal if there is some internal valve body anomalies affecting
shifting. If the pressure readings are correct, and the high shift
points remains; the likely cause is a stuck governor. As the box works
on oil pressure differentials; the governor modifies pressures according
to road speed. Stuck, it tells the box that you are moving slowly -
which, regardless of rpms or pedal position, delays upshifts…
Band adjustments has no bearing on this; with no internal faults -
upshifts are approached by downshift cable adjustments, and with no
improvements then the governor is the next in line…
xj6 85 Sov Europe (UK/NZ)===================================================
The archives and FAQ will answer many queries on the XJ series…
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