A New Auto Transmission Option for P6B and P5B

PeterZRH said:
Can anyone actually confirm it fits the tunnel?
Click to expand...
I've got a Toyota W58 behind the v8 which is a match made in heaven; the single best modification you can do to a p6 IMHO. the ratios are perfect but like all small v8/v6 could use a 6th gear. The Auto P6's are the best donors since the BW is massive and the tunnel is consequently huge.

I'm in the process of grafting a 1uz with an 8hp70 behind it so will let you know how that goes.

EDIT: The ZF TCU's can be replaced with only analogue inputs required for speed & map if desired.
 
Another observation. Until recently I had a 1983 Porsche 928 Euro S - 4.7L, 300hp, 3 speed auto derived from the MB box used in their Grosser 600(5.7L). The rear axle was 2.75 giving 26.9 mph/1000. First gear would run to 100kph at red-line of 6200rpm. The impressive part was that in normal suburban driving the changes were very close to imperceptible.Despite the engine being fairly peaky - it didnt start to boogie until 3500rpm - you could drive quite fast on windy roads without ever worrying about what gear you were in. There was an electric kick-down switch under the throttle that fired a relay on the box to go down a gear if the road speed was acceptable. Many users fitted an extra switch so you could downshift without going full throttle - very civilized.
Anyway, for a 3 speed box it did an excelent job, easy to live with at any speed, probably because its change points had been well matched to the engine's characteristics. Later models with bigger engines (5.4L DOHC 4 valve) had 4 speed boxes, but their deafult mode was to start off in 2nd, despite having final drives as low as 2.2.
Best option for us might be a modern auto with an ecu that has been hacked and one could play with change points to suit their engine and driving style.
 
some time ago i swapped my diff for a 2200 diff gearset. 3.54:1 instead of 3.08:1 I've still got the three speed and run a 2200/2000 speedo for accurate speed readings. The difference in pick up was immediately noticeable, right out of the driveway. The whole car feels lighter and the engine is far more responsive. I do have some ZF 4HP22/24s to put in when I have time however their gearing in the first three speeds is very similar to the BW and GM boxes so there is no gain in pickup other than a smoother operation and the overdrive top is clearly a cruising gear. the half ratio increase will lower the revs at cruise in 4th but provide 3500s ratio first gear with the consequent easier driving and pickup.
 
mikecoombs said:
some time ago i swapped my diff for a 2200 diff gearset. 3.54:1 instead of 3.08:1 I've still got the three speed and run a 2200/2000 speedo for accurate speed readings. The difference in pick up was immediately noticeable, right out of the driveway. The whole car feels lighter and the engine is far more responsive. I do have some ZF 4HP22/24s to put in when I have time however their gearing in the first three speeds is very similar to the BW and GM boxes so there is no gain in pickup other than a smoother operation and the overdrive top is clearly a cruising gear. the half ratio increase will lower the revs at cruise in 4th but provide 3500s ratio first gear with the consequent easier driving and pickup.
Click to expand...
I've long maintained this is the way to do it. Both the LT77 and ZF4HP have MASSIVE overdrive gears. In combination with a tall final drive, they don't work well. Relaxed cruising is one thing, usable gears for driving is another. If it's slightly too low, you could gear it back up slightly with bigger tyres.

I went down from 185s to 185/70s on the original 3.08. That's a 6% drop. The difference is massive because the legal speed limit here on most roads is 80kph/50mph. Before it wouldn't quite hold lock-up and would "hunt" a bit between 3/4. Now it cruises smoothly.
 
colnerov said:
According to my Haynes manual for the Range Rover -

first..........2.480 : 1
second...1.480 : 1
third........1.000 : 1
top...........0.728 : 1
Plus TC lock-up
Click to expand...

There is another gearset option which is
....
First ......2.733
Second .1.562

The remaining gears are the same as per the above post.
Hard to get a hold of now, but I have a few left.
 
Thanks all

I bought one a while ago for the Cresta, but as we're going a different route with that now, I may let Sparky have it.
 
I just remembered, if buying a 2000/2200 diff set, their was a change in the mounting bolts. I forget when or for which diffs but its clear in the manual and parts book.
 
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