DS / SM Auto Box?

C

Chris Dunham

Member
Fellow Frogger
Joined
Aug 31, 2004
Messages
129
Location
Perth
I'm in the dark on these auto's.

Is the auto box as used in DS23's and the SM the same item and can you swap one with the other?.

Whats the max torque figure for this auto?. Are they any good?. Is the final drive ratio that same as the 4 / 5 speed manual or is it taller?.

Thanks in advance for any info,

Chris.
 
Hi Chris,

The box is basically a plain old Borg Warner 35, same as used in Jags, Rovers and Volvos of the 60s and 70s. The only change is that the output shaft comes out the other end - many of the parts can be bought for the above makes, but some of the gaskets etc are different. It is getting hard to source overhaul kits, but they can be found. We had to hunt for an inhibitor switch recently (leaking slightly), but found a source in Europe.

As to power - they were used on 4.2 Jags and V8 Rovers, so they should not be too stressed even on an SM 3.0.

The final drive is lower than the 5 speed (I think its about the same as a D Special), and the ratios on the DS at least are a bit weird - first is very (too?) high - nearly 80 ks flat out, so initial take off is sedate, then second to about 100 ks (110 if you are very insensitive), and they will supposedly do about 110 MPH (sorry the speedo is still imperial!) - I suspect higher, as I have seen 5000 in top and that was 100MPH - it felt as thought it would pull at least another 500+rpm easily, so I would think nearly 120MPH more likely.

The big failure problem on many of the early Autos was that the seal to the separate diff was no good and they leaked diff oil into the gearbox - bad things happened very soon after that :cry:. By the time they got to Australia on the ship many were already stuffed - straight to the workshop for repairs! All have been well and truly sorted by now.

The other issue is simple lack of maintenance -

1) You have to take off the undertray to service the box, so it doesn't get done.

2) It's a Sitrun - must be complicated :nownow:.

Mine was rebuilt about three years ago, and is still commented on as one of the smoothest BW35s around - it is a fairly ordinary Autobox, not the smoothest (but way smoother than the everlasting 4 speed in our W123 Benz :D), but there is no reason why 250K klms should not be a reasonable life if well serviced.

I am pretty sure you could swap one over - on the D the crankshaft for a manual and an Auto is different (and originally the Autos had softer main bearings - go figure :(). You can convert, but you need a good engineer to make up the bits- not sure about an SM though.

We have almost all the worlds remaining Auto DS' - I only saw 2 out of the almost 2000 cars that went by in Paris! We get more than that on a club run.

Paul
 
Last edited:
You must log in or register to reply here.
Top