Hi, I bought a 1972 XJ6 Series 1 about a month ago.

Everything is all good with it, but today I went to reverse out the driveway and..... nothing.
Reverse has just gone overnight.

It's a 4.2 automatic, not sure if it's the Borg Warner model 8 or 12.

My friend at Toyota said it might just be the band is loose,
I thought I would ask some people with a bit more knowledge with Jaguars as
this is the first one I have owned.

Any help is appreciated.

 

Loose band is entirely plausible

I don't know the specific adjustment procedure on either the BW 8 or 12 but someone here will chime in. If not, just Google it. I'm sure the info is out there.

Lacking anything at all I'd gently bottom out the adjuster and then back it off one turn....and call it good.

Cheers
DD

 

I'm assuming BW transmissions work on the same principles as Mercan transmissions. If that's not the case then ignore the following:

If it also doesn't move when you select first gear (Low, wherein the low/reverse band applies) not D which applies a clutch pack, then it is indeed a band issue. But if the band is that loose now it's been slipping for some time and you might have bigger problems.
(';')

 

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As for your transmission

Series 1 up to chasis No 7L.8163 were BW8
Series 1 from 7L.8164 - 7L.16497 were BW12A
Series 1 from 7L.16498 onwards were BW12J

The only book I have available tonight says "No movement when R selected", Incorrect rear band adjustment.

Adjusting rear band, Model 8(BW8) and Model 12(BW12) transmissions
1.The adjuster screw is located on the right hand side of the trans casing. release the lock nut and undo it two turns.
2.Lubricate the screw and tighten to a torque setting of10 lb/ft(14Nm),and then loosen it exactly 1 104 turns and tighten the lock nut to
35 lb0ft(48 Nm)

I have a much more detailed book in the boot of my car but we have a tennis ball size hail storm coming over so I have put 3 cars in a mates garage for the night. Always a problem when we have 3 cars parked outside.




Elinor, the BW12 is basically a ford FMX, when I bought a pan gasket and vacuum modulator for mine they were labelled FMX/BW12.

 

Borg Warner has/is made auto boxes for decades. an American company as far as I know. many brands bought the various versions in the early years of slush boxes.
So, the ford FMX is a BW!!


In addition to a band check, I'd checkout shift lever vs shift lever on the box. The swaging on the cable can fail and result in gear selection anomalies. or the clamping may merely slipped.