Auto gearboxes in the S Type.

[Glyn Ruck]

Yes ~ I've read somewhere amongst my Jag stuff that the Model 8 was in fact an older design than the BW35. The 35 produced more refined change characteristics. Might be another reason they made it possible to lock out that first to second or vice versa change on the model 8. That large first to second ratio change was always a little rough & ready on older transmissions with the possible exception of the good old Chrysler Torqueflite.

So the FG nomenclature remains unresolved and is not a clear indicator of a Model 8 transmission.

[cass3958]

So the FG nomenclature remains unresolved and is not a clear indicator of a Model 8 transmission.

That appears to be correct. So even though my car is in the chassis range according to Davids research and has the FG suffix it has the alloy casing and BW35 on the ID plate.
I have a friend with an even later S Type to mine who I am going to call and get him to check his.

[cass3958]

Ok I done some phoning around chatting to some very nice and knowledgeable people in the Jaguar world and have learnt the following.

Having been passed around a bit I finally got on the phone to Ken Jenkins. Ken is very well known in the Jaguar world , has been a Jaguar engineer since 1967 and know runs his own company http://www.ukjag.co.uk/store/ repairing and supplying parts for Jaguars. Fantastic guy who offered his time to explain the following to me in great detail.

The BW35 gearbox fitted to the S Type was known as the BW35 plus. The BW35 was used in several less powerful cars prior to Jaguar getting hold of it and originally it only had three clutch plates. The BW35 plus had four clutch plates to allow it to be used on more powerful CC cars including the S Type Jaguar.

Ken was fully aware that the Model 8 gearbox that was fitted to the 420 was although older a stronger design to take the power/torque that the 4.2 engine could throw out. The model 8 was also used in the series one XJ6 but Ken has never seen a model 8 gearbox in an S Type and he has worked on hundreds of them. He has no knowledge of the serial numbers but agrees with me that if my gearbox is alloy and has BW35 on the identification plate it is a BW35 not a Model 8 even though the serial number starts with an FG.

We then discussed the fact that my gearbox had been changed and the fact I could not find the 2nd gear hold. I had drive and 1st but nothing in between gearwise just a gate which had to be lifted over to select 1st. Ken stated that that was because more than likely my gearbox after it destroyed itself and was changed the new one came from a Daimler 250V8. They used the same BW35 plus gearbox with the four clutch plates but for some reason the daimler gearbox did not have the 2nd gear. Ken stated that one of the reasons the BW35 gearbox failed was that people would pull away in 2nd rather than 1st. The gap in the selector between drive where you would pull away in 1st and 2 for 2nd gear was so small that many would not notice pulling away in 2nd and this put a lot of strain on the clutch plates cause expensive failures and repairs.

So conundrum solved with regards to my gearbox it is from a Daimler 250V8 of the same period.

Other information Ken gave me was never remove the sump on the BW35 gearbox unless you are doing some serious maintenance as the sump, being made of a very thin material, will warp and leak for ever more unless machined flat. Always use Dextron2 gearbox oil not the more modern Dextron3 synthetic oils. Also the oil should be changed every 10,000 miles, not that many of us will do that amount of miles even in ten years but should be considered if you do not know the service history of your gearbox after purchase.

I will put a link to Kens JAGUK in the suppliers list. He is very helpful and can often supply hard to find parts or suggest alternatives if the original part is no longer available.

[Glyn Ruck]

That is very interesting & Ken is obviously most knowledgeable. Thanks

Regarding lubrication of the 35 plus it's obvious that the friction material on the clutch plates is sensitive to the friction modifier additive packs that are used in Dexron III and above. It has nothing to do with the synthetic base oil that would be a positive. But rather the controlled slip & lock up of the clutches.

While many manufacturers used it, Dexron II was specifically designed for General Motors transmissions ~ Dexron is a GM trademark. Dexron III and above are really Universal ATF formulations that try & meet most requirements, GM, Ford Mercon, old Mercedes etc. etc. From a frictional perspective this makes them a compromise by trying to do too many things. Back in the day Ford & GM ATF requirements were diametrically opposed.

All that said the Borg Warner 35 was designed for use with Type F or G Automatic Transmission Fluids. Fluid meeting Ford specs M2C33 F & M2C33 G. This product offers far greater wear protection than Dexron II & is designed for very little clutch slip & quick lock up. One would expect Dexron II to allow too much slip with potential clutch damage. Of course it would make for smoother clutch operation but at the expense of wear & high temperature generation.

I would run this box on Type F or G Fluid as designed & recommended. If your Dexron II fluid darkens appreciably in service I would get it out of there & replace with Type F or G.

I have also been talking to some experienced Jag people including an old chap that lives close by & used to work at Browns Lane.

So far they have all said that the Model 8 was never fitted to the S Type. What worries me is that they mean SA built S Types which all fall outside David's number range

Is Ken the guy Orlando knows from his incontinent DG service/rebuild?


For Interest see attach. Not the greatest scan but kindly sent to me.

BW_35_manual.pdf

(5.53 MiB) Downloaded 225 times

[Orlando St.R]

Is Ken the guy Orlando knows from his incontinent DG service/rebuild?

Hi folks

No, the chap I have always gone to for help with my DG is Graham Whitehouse at http://www.gwautos.com/.

[Glyn Ruck]

Thanks Orlando.

[JCS]

Glyn and Rob

……”So the FG nomenclature remains unresolved”……

Sorry I am late getting back on this one, but I think it is easy to solve.

In the distant 60’s I worked on a number of auto transmissions and vaguely remember most, but in particular the Hydramatic. That is the GM version built for R-R and the licence built version by R-R themselves, the former type which I ran for 28 years myself in a Bentley.

Some 20 years ago I decided to examine in detail the Hydramatic history with R-R in the RREC archives, taking up about 7 days of research. This included their research on other transmissions and a little on oil types. Leading me at that time, to look at other, now generally forgotten, transmission types, including Borg Warner.

The EG series BW transmission was fitted to the Jaguar 240, whilst the FG type you have, was listed for the Jaguar 340 model, incidentally, I know this data is listed by Jaguar themselves and it is not second or third hand information.

It would not surprise me if that FG type was also fitted in the Jaguar / Daimler, and also if it had additional clutch pack plates to handle increased torque.

Most automatics in the late 50’s to mid 60’s passed through a period of having to design in additional clutch plates. As Glyn has said the Dextron oil range was brought to the market by GM. Others initially unwisely tried to use similar ATF, designated originally by GM for the Hydramatic fluid flywheel transmission that had multiple and simultaneously changeover of the brake and clutch plates between 2nd and 3rd gears. Those companies quickly found the slip characteristics of the Hydramatic clutch and brake packs and fluid flywheel, combining four major movements, were completely different to their own transmissions.

Norman G

[John Quilter]

And there was a four speed BW45 as I recall. The only application I know of was the Hillman Avenger but it did not go into the Morris (Austin) Marina, Rover 2000/2200, or Triumph Stag as I recall. Any other applications out there?

[cass3958]

I think the BW45 was also in the Hillman Hunter. Both Rootes cars.

[Glyn Ruck]

Rob ~ See my question in Harrie's thread. That car looks as though it has a Model 8 fitted due to D1 & D2 in Auto selector quadrant. Would be interesting to know how the transmission is marked on it's plate.