Borg Warner model 12 gear 2 vibration

[Rafa]

1971 US spec. FHC

Vibration felt through car and steering wheel when in gear 2. Gears 1 and 3 drive smoothly.

I have had the car for 6 years, and it’s a recent phenomenon. A removal of the sump cover, clean up, and new Dextron 2 added, plus an auto gear box additive, has not made any difference.

Many thanks.

[Heuer]

You need to check at what RPM the vibration occurs and then drive at that RPM in first and third to see if it is still there. That will eliminate engine speed from the diagnosis.

[Rafa]

Hi David, thanks for the reply.

I’ve driven it selected in 1, no vibration through rev range, and then 2, with continued vibration at all rpms.

I live in Granada, Andalusia, and no-one seems willing to touch classic auto gear boxes!

I’ve been told the ‘band’ might need adjusting but I have no knowledge or understanding of this, sadly.

[AussieEtype]

Check the fluid level as per the handbook - I had a similar issue and it was just low fluid.

[Sdinse]

Band adjustment is relatively simple. Just read up on it in the manual. I believe this is the most likely cause of your vibration.

[Rafa]

Thanks for the replies and sorry for late acknowledgement. Fluid level is fine as I just renewed it, cleaned everything, and added a conditioner; all done as my first step at tackling the issue, but it still persisted.

I’ll research what band adjustment involves!

Cheers, Rafa

[Rafa]

Going back to fluid level, which I've always checked using the rather long-winded published procedure, is there any possibility of false readings due to an air lock of some sort?

I only say this as the amount of gear box oil replenshed after removing sump and changing the oil was perhaps less than expected.

Thanks.

[johnetype]

A significant proportion of the gearbox oil remains in the torque convertor when you drain the sump which is probably the cause of the lower quantities than you were expecting.

[Rafa]

Thanks John, that would explain it. Sadly I had to change the oil as last year a mechanic put Dexron III in instead of Dexron II, which I learnt is a big no-no for this gear box.

I guess if Dexron III was still hanging around in the torque converter, I haven't fully solved the issue!?

[johnetype]

You can get towards a complete change of the oil by doing several drain/refills and driving the car briefly in between, that way the old oil in the torque convertor will be diluted and replaced.

The best way to change the oil completely in one go is to break into the oil cooler circuit and arrange for the old oil to flow out and fresh oil to be drawn in. Normally as the colour changes, you can see when the new oil has made it around the gearbox. At the same time, by selecting drive and reverse (keeping the car stationary) you purge the hydraulic control block. This isn't easy from a safety or technical perspective and involves two people, the car level and potentially up in the air.

I haven't given complete instructions as I haven't done this procedure on a BW 12 gearbox myself, I have done it on "sealed for life" GM boxes. I suggest you do a search including YouTube for any more specific information on doing this on a BW 12 gearbox. Clearly it is very important not to let the gearbox run dry at any point in the procedure.

Personally, I doubt that Dexron II versus Dexron III is the cause of your issue but I can't be authoritative.