Borg-Warner Velvet Drive Transmission

[Guest]

I have a Ford Leyman Super 90HP engine with a Borg-Warner Velvet Drive Transmission. Recently I have had to top up the transmission with about a quarter of a pint of ATF every 30 hours of running. There are no external leaks visible or any ATF in the bilges. I have tested the gearbox oil cooler to 7 bars and am confident that its OK. There is no drain plug in the bellhousing so I cannot see if the escaping oil is gradually filling it up. The gearbox works perfectly. Has anyone had a similar problem with this gearbox and can give an indication as to what I can do to trace the leak before I take the drastic step of taking the gearbox out.

regards,

Colin

 

[david_bagshaw]

We have Bws & have had BWs since 1970, &have never had to top up in season.

Are you absoutely sure no oil is escaping from the cooler?

is it the type with end caps or the solid type?

What condition is the gear oil, dirty/ burnt etc,

leaks to the bell housing will leak out near starter motor, & if in doubt remove SM for a look.

is the box vent jammed / oil residue near it, if latter would suggest perhaps the plates are slipping.

Gear box temp under load? temp difference across the cooler in operation.

If there truly are no leaks the oil can only be going by evaporation, which could indicate dirty cooler, insufficient water flow, slipping plates.

am suprised the cooler stood a 7 bar test as they normaly operate on a low pressure / return I think.

There is an excellent BW agent at penton hook on the thames, we had a suspect box serviced some years ago, (it was ratteling just in gear, turned out to be one blade out of pitch)

David
www.yachtman.co.uk

 

[Guest]

Thanks for your reply.I am currently degreasing the bilges and will then spread absorbent paper under the gearbox and run the engine/gearbox under load for half hour or so to further check on leaks. The fluid was darker than new stuff but no water or white deposits so I am still confident about the cooler. I am lying in Aguadulce in Spain so cannot easily use your repairer. The cooler is the solid type so an oil inlet and outlet and a water inlet and outlet. We blocked one oil inlet and put the compressor hose on the other oil outlet. then submersed the wholelot. No bubbles came from the water outlets so the oil circuit looks sound. I have not found a box vent? I will remove the SM if the leak test is negative.

regards,

Colin

 

[david_bagshaw]

Box vent is on the top usually near gear selector , looks a bit like the top of a biro, and wobbles around.

Your test of the cooler sounds conclusive, would look for slipping plates or lack of oil pressure. leading to slipping & oil vapourisation
You will need a test gague for that, screws into the top tappings near box drive plate flange

Unfortunately BW books on board. How many Engine hours?

Fluid can be dark, not black ,nor smell burnt.

David
www.yachtman.co.uk