4 speed SD1/P5 V8 gearbox ratio's.

dyno · Post by **dyno** » Sat Oct 17, 2015 7:21 pm

To avoid going off topic in my other question I've opened this new topic.

For easy setting up engines on my dyno I always try to use a gearbox in between the dyno and the engine. Easier to fit and engine. (auto boxes are very difficult in use on the dyno)

Plus, I use direct drive in the box for all full load tuning but when I have to map light load, I step down to 3de or even second gear. The reason is, my minimum load of my dyno is not zero. And go up with RPM. At 7000 RPM, minimum load is 150 Bhp !!!. So for tuning (mapping) with almost zero load at 6000 RPM or even more, I switch to second or 3de gear so dyno is making a lot less RPM's. And can even put in neutral for absolute no load.

I've bought an all alloy Rover V8 4 speed gearbox but I have no idea what ratio's are in there. I have to tell the dyno the ratio and this way he calculate the engine RPM to my screen. Anyone?

Second question, are these strong boxes? All I can find on internet about these boxes is, they are very slow if you change gear (not a problem on my dyno) and you better avoid because no overdrive (also not a problem). Is this box as strong as the LT77 or a lot weaker?

thanks in advance,

Dirk

harvey · Post by **harvey** » Sat Oct 17, 2015 7:42 pm

dyno wrote: I've bought an all alloy Rover V8 4 speed gearbox but I have no idea what ratio's are in there. I have to tell the dyno the ratio and this way he calculate the engine RPM to my screen.

Third gear is 1.391:1

Second gear is 2.133:1

dyno wrote:Second question, are these strong boxes?

No, they are made of Lead and Plasticine.

dyno · Post by **dyno** » Sat Oct 17, 2015 7:47 pm

Thanks a lot for the info.

Lead and Plasticine !!! Does not sound strong to me. I hope just strong enough to handle the power on my dyno. Normally water brake dyno's like mine are gently to gearboxes. Hope it will work. It was the only gearbox I could find at a normal price.

unstable load · Post by **unstable load** » Mon Oct 19, 2015 4:47 pm

Try to find an R380 box from a Sherpa (I think it is) and it will be a lot stronger.

dyno · Post by **dyno** » Mon Oct 19, 2015 5:16 pm

Totally impossible to find here. And I believe, even difficult in UK.

ChrisJC · Post by **ChrisJC** » Mon Oct 19, 2015 5:56 pm

Can you not get an R380 from a Land Rover, and throw away the transfer box?

Chris.

dyno · Post by **dyno** » Mon Oct 19, 2015 6:35 pm

Landrover without autobox is also very rare here and when you take of the transfer box you still don't have the drive flange for the propshaft. Possible this can be fixed with 2WD gearbox parts but again, there is nothing to find over here.

unstable load · Post by **unstable load** » Tue Oct 20, 2015 12:01 pm

The Land Rover box is very different. It has a longer input shaft and the output shaft is also vastly different to mate to the transfer case.

What may work is to find the R380 input and output shafts from someone like Ashcroft and fit them to a Landy box.
Ashcroft do a 2 wheel drive R380 but it's sold out for now...
http://www.ashcroft-transmissions.co.uk ... shaft.... http://www.ashcroft-transmissions.co.uk ... parts.html
These guys offer a 2WD R380, but whether they have stock is another issue.... http://www.freewebs.com/tmtransmissions ... his helps.

DaveEFI · Post by **DaveEFI** » Tue Oct 20, 2015 12:46 pm

I'm wondering if a P6 V8 four speed would last a bit longer if all you're doing is selecting a gear when stationary? Of course it will never handle much more torque than it was designed for.

dyno · Post by **dyno** » Tue Oct 20, 2015 5:00 pm

Full power will only be in 4th gear (direct drive in the box). Second and third gear will only be used for light load measuring.

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4 speed SD1/P5 V8 gearbox ratio's.

4 speed SD1/P5 V8 gearbox ratio's.

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