XJ6 & XJ12 Series I, II & III 1968-1992

BW66 Shift points

 
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Old 06-28-2019, 07:54 AM
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Default BW66 Shift points

Now that I've been driving my XJ6, it's time to iron out the shift points. It's shifting out of 1st at about 5mph and out of 2nd at 10mph. If fact, with a rolling stop at a stop sign (nobody around, or a rolling right turn at a stop light), it never downshifts. I'm not a spirited driver. I know, I know, the Jaguar is meant to be driven, but since I'm the one who has to fix it, I don't want to break it. As much as I like working on it, I also like driving it. Anyway... any ideas as to how to get the shift points higher?

Thanks, Bill
 
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Old 06-28-2019, 09:00 AM
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Further info - I've changed the trans fluid with the recommended. And done it 5 times; filter change twice. But these low shift points were there before I changed the fluid. So I'm reasonably sure it's not fluid. The old fluid looked good. No gunk. Also, the up shifts and down shifts are smooth as silk. No clunking.
 
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Old 06-28-2019, 10:51 AM
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page 44-17 of the BW66 Auto Transmission section of the Service Manual shows the more-or-less gear change speeds depending on the axle your car has.
 
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Old 06-28-2019, 10:59 AM
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As the SII came with either the 12 or the 65, my service manual only covers those two. I don't have a service manual that covers the 66.
 
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Old 06-28-2019, 12:38 PM
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go to my website to download it gratis.
 
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Old 06-28-2019, 09:22 PM
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Originally Posted by yachtmanbuttson View Post
As the SII came with either the 12 or the 65, my service manual only covers those two. I don't have a service manual that covers the 66.

The 66 is just a slightly beefed-up version of the 65. They're almost identical.

If you have a 65 (do you?) the shift points can be set higher by ever-so-sightly increasing the tension of the detent cable/shift valve cable. The procedure is the same for 65 and 66 transmissions, so a manual covering the 66 will do.

Technically speaking this adjustment requires a pressure gauge but if you don't go wild with the adjustment you'll be OK.

Cheers
DD
 
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Old 06-28-2019, 10:27 PM
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As Doug said.

I did all mine by "feel", and 3 flats of the double nut arrangement at a time. Sounds boring, its not, as that small adjustment does make things change.

Fiddly as hell and time consuming, but well worth it.
 
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Old 06-29-2019, 06:25 AM
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Also... I just noticed last night. When they swapped out the BW65 and put in a BW66 over a decade ago, they still used the 65's trans dip stick. It is imprinted with a 65. Should I go by it for my 66?

Bill
 
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Old 06-29-2019, 07:37 AM
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This "detent cable/shift valve cable", is it the same as the "down-shift cable"?
 
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Old 06-29-2019, 07:57 AM
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Originally Posted by yachtmanbuttson View Post
This "detent cable/shift valve cable", is it the same as the "down-shift cable"?

Yes ....and no

We're talking about the same cable, yes. But, technically, "downshift cable" isn't quite correct.

The nomenclature gets muddled when discussing transmission cables. Often the terms are used interchangeably.

Some transmissions have a cable specifically (and exclusively) for downshifts. "Downshift cable". "Kickdown cable". "Detent cable"

Others, such as the BW65/66 have a cable that actually controls both upshifts and downshifts. Jaguar (rather erroneously) calls it a downshift cable. Elsewhere it might be called a "throttle valve cable" or "TV cable" or "shift control cable" or similar. The cable actuates a valve in the valve body which alters internal pressure....which dictates when shifts take place.

Anyhow, yes, again, for the purposes of this discussion we're talking about the same cable. I'm just doing some Saturday morning blathering

Cheers
DD
 
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Old 06-29-2019, 09:41 AM
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I'll assume it's only adjustment is up near the carb's linkage. Judging from what I've said about my problem, what thoughts do you have as to whether I first adjust it tighter or looser?
 
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Old 06-29-2019, 09:57 AM
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Originally Posted by yachtmanbuttson View Post
Also... I just noticed last night. When they swapped out the BW65 and put in a BW66 over a decade ago, they still used the 65's trans dip stick. It is imprinted with a 65. Should I go by it for my 66?

Bill

The way the parts are listed in my Series III catalog makes it hard to confirm if the 65 and 66 used the same dipstick. I suspect they are the same.

Cheers
DD
 
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Old 06-29-2019, 09:58 AM
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Originally Posted by yachtmanbuttson View Post
I'll assume it's only adjustment is up near the carb's linkage.

yes

Judging from what I've said about my problem, what thoughts do you have as to whether I first adjust it tighter or looser?
Tighter, as I recall, I'll try to find my old notes

Cheers
DD
 
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Old 06-29-2019, 06:12 PM
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Upon closer inspection my lockdown cable adjustment threaded portion is broken, so I can't do any adjustment. Looks like my best bet is to replace that whole cable before continuing to troubleshoot. So... how complex is it to replace that cable? I've already had the trans pan off a while ago, so if that's part of the process, then no big deal.
 
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Old 06-30-2019, 02:24 AM
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OOPS.

Seen that a few times.

Pan off for cable replacement, and inside the trans the inner simply rolls around a cam, very simple once you eyeball it.

The outer at the trans casing, FORGOT, really, it was so long ago, but will not be rocket science, as the same system was used on the BW35 trans.
 
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Old 07-08-2019, 04:39 PM
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Your broken cable adjuster is the culprit. With a slack or loose cable the trans will shift thru the gears very quickly as your does. With proper tension on the cable, the pressure will increase, thus increasing the shift points and making it shift correctly.
 
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Old 07-08-2019, 05:06 PM
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I presumed that so I ordered a new one and am awaiting it. Then I would need to find the time and inclination. I've had the pan off more times than I care to. But it's what I gotta do. Thanks for the confirmation.
 
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Old 07-08-2019, 05:27 PM
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To set up the TV cable or whatever you may want to call it.
Perform the following:
Throttle Wide open.
Pull the TV cable out as far as it would go.
Tighten adjusting nuts.
The idea being that the throttle cable and the TV cable must be able to work in unison with each other.
If at WOT you still have movement outwards on the TV cable, you have to adjust it to take up the slack.
WOT = TV cable out all the way. The proper geometry of the two cables already exist.
An incorrectly adjusted TV cable will cause considerable wear on the clutches and bands.
A loose TV cable will have the early shifts you are experiencing. Tightening the TV cable will change the shift points. Too tight and you would have a harsh shift.
Once you get it where the throttle cable and the TV cable are working in unison, you can then tweak it to get the shift points where you want it.
 
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Old 07-08-2019, 06:45 PM
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Makes sense to me. The adjustment sounds fairly straightforward. It's the installation that is always daunting. But, I'll get it done. Thanks.
 
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Old 07-11-2019, 06:47 PM
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I don't believe it!! Replacing that cable was an easy job. Took me longer to jack up the car and put the four jack stands under it. Can't check adjustment yet until I get the alternator back down to 12v instead of the 18v. Will do that job while it's still up in the air. Have ordered a alternator rebuild kit.
 
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