BW66 in Mk2 dropping oil

Hi everyone,

I’ve recently had a BW66 gearbox from an XJ6 installed in my Mk2. All going reasonably well, but it seems to have a tendency to lose oil onto the garage floor. It doesn’t appear to be a weep as nothing is there within the 1st day or two after a run. However, leave it for longer, say a week or two, and I come back to the garage to find several 100 mL of fresh ATF in the drip tray under the car.

Does this make sense to anyone?

Thanks in advance…DT

Sounds like a slow leak to me , look directly above the oil in the tray , you should get a idea where it’s coming from , front , back !
Or could it be overfilled with oil , have you checked level after a day of sitting ?

a problem can be the shifter seal, wipe the area clean, and make sure,

its a waste of time changing pan gaskets, if its really the shifter seal,

other possible leaks can be front or rear trans seal, speedo o-ring

Thanks Ian,

I don’t think it’s overfilled. Just checked after a drive and while engine still running and it isn’t even showing on the dipstick, even though I put 500mL in before the drive, with less than that lost on the deck. Even if it was overfilled, where would the ATF come out?


Thanks Tony,

Indeed, the fluid is collecting on the left-hand drip tray (I have two :slight_smile: ), which may suggest the shifter seal. But wouldn’t that be a general leak over time?

Either way - I’ll get under and have a good look.


The shifter seal is a real mongrel thing to change, as it needs +4" clearance from the outside of the trans to sheetmetal, as the shifter shaft needs to come out. In my case I had to do this with trans out (on a bw8)

If the pan gasket was not leaking with trans on the ground, it probably wont be that.

anyway, wipe the area directly under the shifter seal perfectly clean with rags, come back later and inspect with a bright light, if there is red trail, you have found the culprit

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That’s great thanks Tony.

I’ll do all that…weekend job; here we come :grinning:

You can add a dye to the oil that shows up under black light. Really effective at identifying leaks. I got mine on Amazon but I am sure it is available from lots of suppliers. You can also get dye for adding to your water…

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Was the transmission rebuilt prior to installation? The pan is notorious for leaks. The used, yet to be rebuilt, BW66 I am using has a massive amount of sealer on the pan. Can you access the band adjusters?

I am currently making this conversion. Is your car LHD? Did you keep the steering column selector lever? If you did I would appreciate photos of the gear shift cable. Thanks.


My BW66 will leak after two weeks so the drip must come from above fill level. I assume.
The shift, or throttle cable is on the left, it has an O ring but sits quite high. You can just maybe make it out from above. The pan seal should leak all the time, shouldn’t it?

Thanks David,

Sounds like we may have similar issues. Certainly, my symptoms would align with oil settling above a given level over time and then leaking out from a seal, such as the shifter.


Thanks Bob,

Car is RHD (Australia). It was recently fitted, but don’t think it’s the pan. There is some fluid around the seal there, but fluid is from above and settling along the pan seal then dripping.

Yes - we kept the column selector. I put stainless extractors on it that are suitable for an E-type. However, they had to be slightly shortened to fit. As such, due to the clearance (or lack thereof), the shift actually works in reverse (Park is on the right). New indicator made up on the column shift.


If your BW66 is leaking transmission fluid after sitting for a period of time it may be that ATF is draining back into the transmission case from the torque converter. This will raise the level in the case and then if any of the seals to the outside are not working you will have a drip from that seal. Some BW66 have an anti drain back valve inside of the transmission to keep the torque converter from draining back into the case
Either way the leak is from a seal and or the pan gasket. Pete
Jaguar calls this valve a " non-return valve "

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It is a ball bearing ball with a little spring. Does not hold back all the oil. The question in case is though why his is spitting out so much! For me it is a few drips… did somebody forget the seal?

To get the column selector to function as normally the lever on the trans should be oriented 90 degrees from designed. The lever should point downwards rather than up. The BW66 was made to work with a console selector with the selector cable approaching from the rear.

What are e-type stainless “extractors”?



Hi jag060. I realise this is a very old post, but did you ever resolve this oil leak DT?
I’m looking to install a BW66 in my Mark 2 & would like to address all the leaking culprits before it goes in.

Thanks Pierre

It effectively went away by the looks of it. Can’t 100% explain it, but the theory is, when the car sits for a while unused (only several days to a week or so), the oil flows back from the torque converter and may have resulted in an overfill situation??

The mechanic who installed DID inspect and tighten a few bolts around one of the flanges/seals, though it did still leak afterwards…but now stopped. Maybe the combination of tightening and some seal swelling has resolved the “true” issue??

All the best with your BW install :smile:


Guys, with this conversion do I need to use the XJ6 Speedo Cable or will the 3.8L speedo be OK. Not sure on the Number of teeth variance on the drive cog?
Also, I think the XJ6 had a removable panel on the side of the tunnel to allow in car access to the throttle linkage on the side of the BW66. Did you guys cut this opening in the MK2?
appreciate your feed-back

Hi DT, I’m keen to know if you used a transmission mount from an XJ6. Can you confirm what mount you used & if you have a photo that would be very useful.