automatic boxes

[Colin McA]

Hi,

I am looking for some information relating to my autobox.

I don't have a reverse gear so will need to take it out for a repair.

I have been offered a BW box from an Aston Martin, ( year and model unknown). it does look like a bw35.

Does anyone know if this will be a bw35 an is there any difference between the AM and the rover specs? obviously the bellhousing.

I would love to get my own refrubed but the aston box will cost me much less.

Any suggestions.
Colin

[harvey]

If you've only lost reverse it might be worth taking the sump off and having a look inside. There are things that can fail which can be fixed with out removing the box.
If the AM box is BW 35 the bellhousing will interchange but I would think the tailshaft is different.Changing this is a box strip.
You could if you were lucky use the parts from the two boxes to make one good one, but you'll still need at least a gasket and seal kit, plus labour for someone to do it.Whatever anyone else tells you there are some things that need doing when overhauling that can't be done without special tools.

[Phil Nottingham]

Model per model eg BW65/BW45/BW35/DG are all the same interenally but they have differnt outpu/input and valve bodies to suit the manufacturer.

The BW35 is readily available and can be reconditioned to as new Rover spec so there is no need to swap.

G Whitehouse can do conversions I understand - I do not know whar model of box the AM had it may not even be BW - could a GM Hydramatic or a ZF

[Colin McA]

The box is definatley a borg type but the numbers are all on an aston martin plate.

It was just one option I am looking at. the other is a auto box from a p4. If I got a box the aston box for £75 it is a bit of a saving on the hundreds to overhaul, it would also give me an option to drive the car and get the original done in time.

The only other fault with my box is that it doesn't seem to have park either so it may be a rod somewhere.

I have a copy of the autobox manual so will have a look.

Cheers
Colin

[Phil Nottingham]

The "auto box" from a P4 is not like any other auto box its just an electrically operated manual box/overdrive with a torque converter. quite ingenious really but not suitable at all for a V8. It was designed for a 2.6ltr engine anyway.

if there is no Park its likely that the sprag has broken off due to some engaging it while the car was moving. Unlike the DG box there are no safety devices to prevent this.

The reverse gear could if you are vey lucky be an adjustment of the brake-band (easily sorted) - faulty valves again substitution of another valve block is dead easy or a broken servo. I think this can be replaced without removal and stripping down as can the valve block.

Using the box in this condition will only make matters worse

[Colin McA]

I saw a guy selling a p4 box on ebay.

It looked like a bw35, I checked the number and it is a bw65 so he is wrong.

What I want to know is, the bw35 was fitted to various cars like the triumph 2500. are the internals all the same? did the manufatures then match the box and engine with a rear axle ratio?

Colin

[Phil Nottingham]

I think the internals are basically the same model per model the differences being on the output shaft extension housing and the valve bodies to give the differing shift patterns.

The plate on the side will give the model eg 3FU, 7FU amd 330 etc. I think its safer to use one that was fitted to the V8 Rovers - they were also used on the Mk3. The Mk3 used the box with a rear pump as well as the front pump which means it can be tow started.

The BW 35 was used from the mid 60's to late 70's on all sorts of cars but improved all throughout this time eg self adjusting bands etc. The BW 35 was a lightweight and was suitable for smaller engined cars like the Austin Cambridge. The torqu converters may also differ

The BW 35 was never used in P4's as it was not in production at the time of the P4 - the only BW box was the DG which is much bigger and heavier this too was used in many up market British cars of the late 50' early 60's like Mk1 Jags

[harvey]

The best BW35 box to use is the 303 series, this was introduced by Rover into both the P5B and P6B, so both models had the same unit. At the time of its introduction if you purchased an exchange box from Rover you always got a 303, regardless of what you had to send back on exchange, so a lot of the FU and 267 series disappeared back to the factory, never to be seen again!

[Colin McA]

I am sure I read on the borg warner website that the bw35 was introduced in '61.

colin

[Phil Nottingham]

May be but it was untested and as I said aimed at smaller engined cars - Rover stuck with the DG till late 65

[dorsetflyer]

1961 could probably be about right as my 61 Ford Zodiac MKll had a BW35 fitted, and I cannot remember them any earlier.