BW65 bolt-on overdrive

[DanDanTheGardeningMan]

On page 112 of the technical reprints in the members area, Paul Todd writes of an overdrive conversion for the BW65 box, basically adding a J-type laycock overdrive, shorter prop and different rear casing for the BW65.

Does anyone know more details of this conversion. Who did the kit etc?

I want to keep the BW65, and fancy being able to switch in the overdrive when and if needed. This American company does much the same thing:

http://www.gearvendors.com/custom.html

I don't want to change the diff to a 3.45 or change to the ZF box, so any info on this conversion appreciated -unfortunately it dates from 1986!

Thanks

Dan

[alan_thomas]

imported post

I know there was a Volvo version of the BW35 that had an overdrive unit fitted to give if 4 speeds. It was fitted to the 240 and some other models.I think itwas called the AW70 . But before you go and hunt one down the overdrive was fitted between the bellhousing and the main autobox casing and added about 8 inches to the overall length of the box.

The american link you posted mentions they can fit an overdrive onto the back of a ZF box but they menetion it must be the 4x4 version (like the P38 rangerover boxes). I assume that would make 4 + overdrive and give it an impossibly high top gear!

- Alan

[KOY 23]

imported post

Dan.

In response to your earlier comment about the "ZF constantly changing gears on A roads" I think the answer depends on how tight you have adjusted the kickdown cable. The ZF is much more responsive than the BW 35 and will change down as you slow down, it also has "part throttle kickdown". If the cable is tight it will change down earlier and hang onto revs. A loose cable will give a much more relaxed change pattern. So if you have it tight and driving method is heavy on the accelerator then I am sure it will be up and down like the proverbial. Progressive accelerator action and looser cable and it is everything you want.

John.