Upgrading the P6 gearbox - Plans to fit new gearbox

G

gully

New Member
Hi there,

I have plans to upgrade the existing 3 speed automatic gearbox in my 1976 3500 P6 to either a 4, 5 or even one of the latest 6 speed automatics from a suitable donor vehicle.

This upgrade will be done when I install an upgraded Rover motor (with stroker kit).

I would appreciate knowing if any other owners have placed upgraded automatics (as above) in their cars and lessons learned.

Thanks



GULLY (In Sydney)
 
Hi Gully

Easiest modern auto to use is the 4 spd ZF HP22 as used in the Range Rover (4WD Rear casing) and LDV 400 Ambulance (2WD rear casing) in cable control form and the Jag XJ40 in both cable control (check - not 100% certain on that) and in electronic control J Gate form.

This box has a nice tall overdrive 4th ratio and lock up on the torque convertor. It is arguably a little weak (Despite also being used in the p38 4.6) if you have a really stonking 5 ltr to run with it, but it is possible to upgrade the internals to HP24 spec after which you have massive torque capacity.

Installation of the box is not really difficult at all. You'll need a new engine end for the exhaust of course to get round the differently shaped bulk. We used a mildy chopped BW35 rear cross member without difficulty. And you'll need to shorten the prop.

Biggest advantage is the availability of the bell housing, engine to torque convertor mountings etc ex LDV ambulance and Range Rover.

The two areas where thinking caps did have to go on were the change lever arrangement on the transmission tunnel and the speedo drive. Initially we used a Range Rover Classic change lever, but this stands very high above the tunnel and I wasn't happy with it aesthetically. Cable routes to the box were difficult as well. That and a knackered box needing an overhaul has persuaded me to change horses and go for a Jag electronic box. Jury is still out on the ease or otherwise of sorting out the wiring loom! The speedo drive we solved for the ex LDV box by machiing a BW35 speedo drive to fit into the ZF box. I haven't checked yet with the Jag box.

Note you must start with an automatic car as the transmission tunnel is much larger! (ditto if you wanted to put in a 5 or 6 speed manual box!)

Happy to help with any other specific questions if needed!

Regards

Chris
 
Hi chris,

Thanks so much for this detailed response to my 'gearbox' post which I will now pass onto my Rover mechanic who has given me fantastic support to date as I continue to develop my car.

I took the Rover to the trimmer yesterday about an hour north of Sydney and expect to have the car back in about 4-6 weeks with a full leather refit including doors and new carpets.

My Rover is indeed an automatic.

I have also been contacting some auto tranmission specialists here in Sydney to see what options they come up with, and want to explore the potential to install a triptronic gearbox for my car........anything is possible if you do enough research !!!!

Again many thanks !!!!

GULLY (In Sydney)

Many thanks
 
Hi chris,

Thanks so much for this detailed response to my 'gearbox' post which I will now pass onto my Rover mechanic who has given me fantastic support to date as I continue to develop my car.

I took the Rover to the trimmer yesterday about an hour north of Sydney and expect to have the car back in about 4-6 weeks with a full leather refit including doors and new carpets.

My Rover is indeed an automatic.

I have also been contacting some auto tranmission specialists here in Sydney to see what options they come up with, and want to explore the potential to install a triptronic gearbox for my car........anything is possible if you do enough research !!!!

Again many thanks !!!!

GULLY (In Sydney)

Many thanks
 
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