I have a 40,000 mileage 420G with the BW 3 speed auto box. I just want to get an idea of what sort of speeds should produce what revs as the car has a really high rev at motorway speeds.

As I pull away and accelerate, it feels that I get two gear changes, one around 10mph then another at 20-25mph then that is it. As a result, the car is doing approximately 4500 revs for 65mph - which is almost red lining and I'm sure is completely wrong.

The car has had some changes over the years (No major changes under my watch, except electronic ignition) and I don't know if the rear diff may have been changed? I'm not a great technical man, so any suggestions may have to be explained with kid gloves, but I chatted to a Bentley owner the other day who also had the 3 speed and he said he cruised at 70mph with 1800 revs, (I appreciate different engines/torque) but it seems a much more appropriate level!

Someone has suggested that it may not be moving up into third gear - but I do feel two changes - should there be three changes?

Any suggestions would be gratefully received!

 

Apart from somebody fitting completely the wrong diff, the only other thing could be the torque converter is slipping due to wear in the one-way clutch. Then there are the brake bands in the gearbox, these might need adjusting but that's a rather longer shot.

 

 

Thanks for the replies - first stop... Looking at the rear diff and finding out what it actually is...

 

From the Mark X manual:

In D1: Upshift from 1st to 2nd at 6-7, 2nd to 3rd at 10-12. Starting in D2, shift into 3rd at 10-12. These are both for minimum acceleration.
The BW8 has a 3.54:1 rear axle ratio. The manual shows 2780 rpm at 60 and 3241 at 70mph. My Mark X tach shows 3200 at 68 mph.

Phil

 

Stupid related posts. Mods, please make this “feature” optional!