Bw 35 and 65

Tony58

Member
Hi All. There seems to be a glut of Bw 65 boxes on ebay and elsewhere, my 35 is sat on the bench and I'm wondering whether to swop it, cost wise I know a guy in Keighley who will rebuild my 35 box for £300 and I'm also aware that if I buy another box I've no guarantee if it will be any good. What to do, the 65 looks differant to 35, can anybody offer advice and why can't I view the pictures of the 35 rebuild that was posted last year on the forum tony
 
I haven't seen a P6B BW65 on EBAY for a long time, they're mostly Jag, and they won't be a straight swap. The proper Rover one is a straightforward swap with just a few minor mods. Secondhand boxes come with risks.
 
Hi Harvey, I'm showing my ignorance I thought a 65 out of a jag would be a suitable swop by changing the bellhousing
 
I'm showing my ignorance I thought a 65 out of a jag would be a suitable swop by changing the bellhousing

Not that simple, the tailshaft and tailshaft housing are different, so you'd need those from a P6B BW65, and you'd have to totally dismantle the box down to the main components to swap them over.
 
Harvey, What cars were fitted with the BW45 4 speeder? I've wondered if that might be an easier swap but suspect they will be like hen's teeth to find.
 
BW45 was fitted to Chrysler UK models, but it won't really give any benefit as the fourth gear isn't an overdrive.
 
Then perhaps it might be worth for a 4 cyl Rover in combination with the V8 final drive.

Could be, but you'd have to research the ratios. If first was about the same as the 35 the 4 pot would probably struggle to pull the taller diff. I would imagine they used the same size clutches and bands as the 35 & 65.
 
Some info on the BW45. The gear ratios were suitable, but the fact that it was a very different animal altogether, makes it unsuitable for any Rover application.

Motor Sport Magazine, October 1972:

Page 58 of October 1972

A new Borg-Warner automatic gearbox.—We went down to Port Talbot, braving the distinct possibility of getting irretrievably lost in Swansea on the way home, to see the impressive factory which Borg-Warner have erected on the new Kenfig Industrial Estate just off the A48 (M) road, where they are introducing new methods of production of their automatic transmissions in a fine new building of some one-million square foot floor space.

The main purpose of this move to Wales is manufacture of the new Type 45 four-speed Borg-Warner automatic gearbox, for cars of up to 2-litres, which will eventually supersede the well-known Type 35 three-speed box. We were able to sample the Type 45 transmission in a fuel-injection Volvo 144 which, together with a 1.3-litre Morris Marina, are being used for development and demonstration purposes, and the smoothness of the changes in this closer-ratio gearbox was most apparent. It marks a notable step forward in using plate clutches instead of the difficult to keep in adjustment band brakes of the earlier gearbox and it is significant that pressings replace castings for many of its components. The design, it is pleasing to note, stemmed from this country rather than from America and the new Type 45 box will also be made as a three-speed Type 55, which Toyota are using at present, the casing being sent to them from the Welsh factory.

The production methods at this impressively spacious factory, where 1,500 operatives work, a number to be doubled when the full production of 1,000 Type 45 and 500 Type 55 gearboxes per day is achieved, are most interesting. For instance, there will be an 83-stage transfer machine, supplied by Lamb of Ontario, for machining the aluminium gearbox casings, which needs but three operatives to oversee it. Two 1,000-ton Wilkie & Mitchell presses stamp out clutch cylinders, to a ready-to-use state, with no subsequent machining involved. There are nine stations per press. In contrast to this automation, women operatives fit the rotor blades by hand. Components will be conveyed about the factory on roller-coasters, and J-pattern travelling jigs will facilitate assembly, right up to the dispatch stage. Completed gearboxes are all tested on A. T. & T. dynamometers, having been balanced electronically while revolving at 1,100 r.p.m., their heavy-point marked with a blue spot for the guidance of the car manufacturer fitting the box to his engine.

The gear assemblies are electron-beam welded, each being completed in 4½ seconds, the weld being made in a vacuum, using Scieky apparatus, which obviates any distortion or interference with the heat treatment of the gear pressings. Before welding, the components pass through a Raydne washing vat.

Even a brief inspection of the new Borg-Warner plant shows that the company plans a big expansion. Apart from the new gearbox, it supplies BMW, Saab and Citroen with automatic transmissions, while the applications of the Type 35 B-W box to British cars are too well known to need enumeration. B-W claim to have well over 5-million units in use and to serve more than 80 manufacturers in eight countries. They are seeking customers for the new Type 45 transmission, which has ratios of 3:1, 1.94:1, 1.35:1 and direct-drive, against those of 2.39:1, 1.45:1 and direct drive of the Type 35 box. Aluminium is now used for all automatic gearboxes intended for cars of up to 4-litres, although cast-iron casings are found in the XJ6 and XJ12 Jaguar transmissions.

There is also a SAE paper on the design:
Borg-Warner Automatic Transmissions Model 45 and Model 55
 
I've just looked and the 45 & 55 used bigger diameter clutch plates than the 35 & 65, but the 55 was only used by Volvo, and I only ever came across one 45 in a Singer Vogue, and one in a batch of new Chrysler gearboxes I bought, so the plan for the 45 to take over from the 35 never happened.
 
I had a trip in a Sunbeam Talbot (crappy Avenger derived hatch) with a 45. I remember being surprised it actually had 4 speeds and how smooth it was. I wonder what the internals are rated at.

The obvious answer is fit the ZF. Better than all of these as you would expect for 30 years development over the BW. I can't stress enough how much a difference the lock-up makes while cruising. Remember you lose 40-45 bhp with the auto and only 20 or so with a manual transmission. Basically you get all that back which helps keep you in top gear. The solution isn't quite perfect as overall the diff is about 10% too tall. Rover stretched that 3rd gear with the BW box which isn't needed when you have a 0.73:1 ratio in the box. 33.7mph per 1000rpm is just silly.
 
I was told that if I wanted to swap my 35 for a 65 I would have to change to a shorter drive shaft, is this incorrect?

That is incorrect. You just to need to use all the parts associated with the BW65 which means fitting a bracket to the underside of the tunnel to mount the selector cable.
 
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