A New Auto Transmission Option for P6B and P5B

#1
There is news from Down Under in Australia...... A second automatic gearbox has been identified that fits and works readily in P6B (and P5B). In the UK and Europe, the upgrade to a ZF HP22/HP24, sourced from a Range Rover, is an established retro fit. That gives an additional overdrive 4th gear and lock up on the torque convertor. Both highly desirable. But the ZF has a very clear idea what gear it's going to let you drive in, it isn't possible to back off the throttle to encourage the box to change up.... So while it's a huge improvement, it isn't the perfect solution.

The Holden VN model Commodore came with a 5 litre V8 and a GM Turbo 700 4 speed auto, cable controlled and with torque convertor lock-up. The big news is that an adaptor has been identified to couple this transmission to the Rover V8. I've linked the supplier in the first reply below.

Given this adaptor, it should also be possible to source the transmission from the USA.

22310181_10212379623019201_2100221757685790346_n.jpg

The adaptor is supplied here:

Rover v8 - BELLHOUSINGS & ADAPTORS

Further info on the transmission here:

GM Transmission Resource

and here:

Turbo-Hydramatic - Wikipedia
 

PeterZRH

Well-Known Member
#3
I did wonder whether the SD1 GM180 housing would allow other transmissions without such an adaptor. I'm not sure either any of the non-electronically controlled GM transmissions have a lockup function. Which would be a huge downer.
 

unstable load

Well-Known Member
#4
The 700R4 has a locking tq converter, plus I am certain that some enterprising hot rodder has found a way to
manually shift the later boxes to use in his muscle car without the electrickery boxes.
 

ghce

Well-Known Member
#9
There is news from Down Under in Australia...... A second automatic gearbox has been identified that fits and works readily in P6B (and P5B). In the UK and Europe, the upgrade to a ZF HP22/HP24, sourced from a Range Rover, is an established retro fit. That gives an additional overdrive 4th gear and lock up on the torque convertor. Both highly desirable. But the ZF has a very clear idea what gear it's going to let you drive in, it isn't possible to back off the throttle to encourage the box to change up.... So while it's a huge improvement, it isn't the perfect solution.

The Holden VN model Commodore came with a 5 litre V8 and a GM Turbo 700 4 speed auto, cable controlled and with torque convertor lock-up. The big news is that an adaptor has been identified to couple this transmission to the Rover V8. I've linked the supplier in the first reply below.

Given this adaptor, it should also be possible to source the transmission from the USA.


The adaptor is supplied here:

Rover v8 - BELLHOUSINGS & ADAPTORS

Further info on the transmission here:

GM Transmission Resource

and here:

Turbo-Hydramatic - Wikipedia
Cool more options is always good, my only concern is that we are replacing old boxes with only slightly newer ones when we could be using 6 speeds and up, I know that there is a reticence to get involved with electronic shift computers but the shift computers on offer are aftermarket and designed to be user/ amateur friendly for install and set up.

**EDIT** here is a link to an earlier thread 6 speed auto should be now possible, also some interesting options especially for Toyota boxes as there are some bell housing conversion kits available to fit Rover V8's

Graeme
 
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unstable load

Well-Known Member
#10
Cool more options is always good, my only concern is that we are replacing old boxes with only slightly newer ones when we could be using 6 speeds and up, I know that there is a reticence to get involved with electronic shift computers but the shift computers on offer are aftermarket and designed to be user/ amateur friendly for install and set up.
Here's a crowd in SA that does controllers.
Gearbox Controllers
With the exchange rate these days, it'll likely be cheaper than a case of beer...:rolleyes:
 

PeterZRH

Well-Known Member
#11
Interesting. Clearly the more gears the better. One of the big problems I identified with the tall rear axle is that you really don't have usable gears at real road speeds. The 1:1 gear is still 24.7mph/1000rpm. This means you only really have two actual gears in the power/torque band of the engine at legal speeds - in fact really only a single gear if you think of first as a "get you moving gear". You really feel this on twisty roads, coming out of corners, you simply don't have the right gear to accelerate out and the car feels ponderous. Similarly raw acceleration is very much more modest than you'd expect - this of course remains true for the standard BW transmission or the ZF which simply adds an overdrive ratio. What is obviously needed are intermediate gears.

I'm hoping to put the 4 cylinder final drive in my ZF car which hopefully will alleviate the situation somewhat. As a word of caution, many transmissions with more than 5 gears tend to offer extra overdrive ratios. There's a danger that you simply end up with more unusable ratios at normal road speeds and gain little in drivability without similarly changing the final drive.

There is no car with the RV8 engine which attempts 33.85 mph/1000rpm gearing that the ZF transmission gives. In fact I know of no car except those with genuine 160mph+ performance and actually need this or some very recent models with 7, 8 or 9 speeds to play with.

In other words there's more to this than dumping a complex transmission into the car because at the end of the day it is compromised by the original set-up. Ultimately a standard Rover V8 only puts some 100bhp on the road through n auto.
 
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#12
Sounds a bit like lorries with a dozen or more gears. When empty the majority of them aren't needed. Only when loads are carried do they become necessary. Obviously extreme weight differences are inherent in that application but rather less so in a P6. Five gears would seem more than adequate to me. :D
 

PeterZRH

Well-Known Member
#13
Well GM have a 10 speed transmission now. The first car I didn't miss a manual gearbox was a 5 speed BMW 528 (E39), it was notable superior to the 4 speed ZF in in the earlier E34 I had.

It would seem to me it's about efficiency. Mercedes claim the 9 speed gives 16% better efficiency than the transmission it replaced. I guess that's only possible with tight integration with the engine management and not likely something you'd achieve at home with a 3rd party box of tricks and a 50 year old engine.

So I'm supposing 5 would be a real improvement on the 4 speed ZF but I doubt going further would delivery much appreciable benefit. These boxes also feed back to the engine an feather the throttle for smoother changes and many other things. In fact it is better to think of the engine/transmission as a single unit.
 
#14
Any gearbox with an overdrive top gear - less than 1:1 - is going to leave you very high geared.............

But there's a double win available. It isn't only the diff and box that determines overall gearing - the rolling diameter of the tyres is in there too.

So, fit tyres that are undersize on rolling diameter. Gearbox raises the gearing a lot, smaller tyres brings it down a little. PERFIK.

Better still. Smaller rolling diameter tyres reduce significantly the problem of fouling on the inner side of the D Post........... You might even find you can go bigger than 205 width as a result....... Or be able to use wheels of non ideal offset..........
 
#15
Peter is a fan of modern multi gear auto transmissions.
So am I.
But not behind a Rover V8 that retains most of it's broad power band. There isn't really a "sweet spot" in the engine's power delivery, so it's silly to try and keep the engine spinning at a particular rpm.

I reckon four gears is more than adequate. But I'd be open to persuasion to go for five. Seven or ten is just silly and ruins the character of the car without delivering any noticeable gain.

So my selection criteria is based on:
1 - overdrive top gear
2 - lock-up on at least top two gears
3 - minimal aggro in the control department.

Unless you've converted the engine to run with a proper aftermarket ECU and fuel injection, you risk having to install a good raft of the sensors for an ECU just to operate an electronic control box.

So I'm inclined to aim for that sweet spot where boxes have lock up and overdrive top but are still on mechanical control. And they seem to be all four speed. ZF and the GM 700R4 are known. Other offers more than welcome..............
 

PeterZRH

Well-Known Member
#16
I's agree with that. One of the nice things about the 4HP is that it doesn't alter the fundamental character of the car. Indeed put it in "3" and you are exactly where you were with the standard transmission. Actually perhaps not really as you seem to have less control over the shift with the throttle than with the BW. Maybe that's a question of adjustment in my case but it seems to want to change up and stay there more than before.

It's a slightly odd experience driving a modern 9 speed car as it shifts about much more than you'd expect as it optimizes for economy. Certainly at motorway speed, it shifts between 3 gears with very small changes in throttle or road conditions.

As far as the gearing is concerned. If you fitted 195/60 tyres it's be about right. No doubt on 6" SD1 rims this would would do wonders for handling but 60 profile I fear would look daft.
 
#18
"I'm sure you need to adjust your kick down (throttle position sensor), it really does make a big difference to the behaviour....."

Is Peter's box electronic, then? I thought he had a mechanical control box? HP22/24, not HP22/24E?
 

PeterZRH

Well-Known Member
#19
It's the same as Warren's all mechanical. I think some adjustment might be necessary bu the engine itself needs tuning first. It noticeably leans out with aggressive throttle and this I think work against the box which expects a more linear power delivery.

The one real reason I can really think of with a multigear auto in a P6 is if you can also rig-up a tiptronic and play!
 

Cafcpete

Active Member
#20
"I'm sure you need to adjust your kick down (throttle position sensor), it really does make a big difference to the behaviour....."

Is Peter's box electronic, then? I thought he had a mechanical control box? HP22/24, not HP22/24E?
No it a normal box, I simply put TPS because in reality that's what a "kick down" cable is. When the cable is set correctly the box is a joy. I have 3 months left to go on my medical driving ban, but my nephew has driven it and says how responsive the box is to changes in throttle. Can't wait till I can try it myself!
PeterZRH is right, It does help having you engine in a good state of tune, but that is the same with any box.
 
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