I'm new to this forum, in fact new to any forum, so hoping for some assistance.
My 1973 Jaguar XJ6 has delayed shifting into 3rd gear. It shifts around 30 mph, but only after driving about 3-5 miles from a cold start. The modulator has been changed but the Jaguar service manual indicates that if the BW T12 modulator is changed the pin must also be changed and I am thinking that the manual is indicating that the pin would need to be changed if the modulator was changed from non adjustable to adjustable modulator. The adjustment screw is almost all the way out, so no further adjustment is possible.

Any thoughts on the subject would be appreciated.

 

It *might* be old fashioned morning sickness that has been known to plague some transmissions...tho I'm not sure if the BW12 is one of them.

Old sealing rings on the shuttle valves, oil pump, etc get hard and prevent the fluid from going into all the right places. When a bit of warmth sinks in they soften....and...voilą !...starting doing their job again.

Cheers
DD

 

Thank you Doug. Hoping that is not the case as I am not able to rebuild the unit at this time. I had better response from the transmission after an incomplete fluid change with the shifting occurring after shorter mileage, after the change. Sucked about 2/3 rds of fluid from torque converter and pan. Helped quite a bit.

 

Doug is right, and you appear on teh right track.

Suck it out again, and it should be better still.

The 4 odd litres at each fluid service barely "refreshes" the total capacity at all.

Multiple "drop and refills" to about #7ish usually gets the new fluid concentration into the high 80% mark.

This has rejuvinated all of mine over the years.

Only trans I ever replaced was the BW12 in Sir Aurthur, when it became a 2 speed, 1st and 3rd only.

 

IF Valvoline Maxlife Dex/Merc is suitable for your transmission
you may want to use that in the recommended drop/refills. It is
available inexpensively at Walmart.

The Valvoline Maxlife line is targetted towards vehicles with higher
mileage and contains additives to swell seals etc. The specific one
mentioned above is compatible with most Dexron and Mercon specifications.

The complete information can be found on the Valvoline site or
the back label on the jug.