A Dunny Door Question

[101RRS]

I have fitted a 5 speed getrag manual gearbox out of a V8 VT Commodore to the back of my V12 Jag engine.

While the conversion went OK one of the things I didn't take into account was that the commodore has an electronic speedo and as such the gearbox does not have a speedo drive. It has a magnetic sensor on the back of the box that counts either the prop shaft uni knuckles or something else to provide the pulses to the speedo. I have a programmable VDO electronic speedo but the speedo guy seems to think that four pulses per revolution is not enough to provide accurate speed inputs - the more pulses the more accurate the speed readout, particularly at higher speeds.

I have tried to get information out of the local holden dealer without luck - so does anyone know what the speedo pickup counts or where I might be able to find out the information - such as a forum. The gearbox was also fitted to V6 holdens until recently. The gearbox was used in the V8s for a short period of time after the T5 was used in the VS but before the 6 speed was introduced when Commodore went to the 5.7l V8s.

Any ideas would be appreciated.

Thanks

Garry

[BigJon]

Get hold of Mal Wood, he is a gearbox and conversion guru. I will try to find a number for him.

[BigJon]

(07) 4661 3548
(07) 4667 0548

[rangieman]

First off why a getrag ?:eek: yuk they are almost as bad as a T5 in my opinion and i should know i work for holden but the info you request i cant help with but i will say pm (moose) he might be able to help you:D

[101RRS]

First off why a getrag ?:eek: yuk they are almost as bad as a T5 in my opinion and i should know i work for holden but the info you request i cant help with but i will say pm (moose) he might be able to help you:D

Thanks BigJohn.

Rangieman - at the time it was the only gearbox that was realistically available. It was brand new and real cheap. I appreciate the gearbox as marginal for the V8 but the V12 has less torque and the getrag has a decent 5th gear.

The old T5 could not handle the power in 5th gear, the more modern Supra Gearboxes were not available at the time, the bottom 4 gear ratios of the Getrag are almost the same as the jag 4 speed and most importantly the gearbox is short and doesn't have a long tailshaft housing with the gearshift inbuilt - the gearshift is not part gearbox housing which is important in a jag as the gearshift sits right up near the bell housing. Likewise the holden V8 at the time only produced about 10kw less than the jag but a lot more torque so the gearbox is able to handle what the jag had on offer. Its biggest downside is that the bell housing is part of the gearbox housing.

For sure if I was doing it now - I would look at other options but at the time there was not much available that could handle the power at a reasonable price. The box came from HSV and was pulled out of a Holden being converted into a HSV where they pulled out the new gearboxes and put in Hollingers.

I wouldn't mind putting in a 6speed but the holden V8 with its torque has problem pulling it in 6th gear and any reasonable speed so I doubt the lower torqued V12 would be able to pull 6th gear reasonably at anything resembling legal speed.

Cheers

Garry

[rangieman]

Thanks BigJohn.

Rangieman - at the time it was the only gearbox that was realistically available. It was brand new and real cheap. I appreciate the gearbox as marginal for the V8 but the V12 has less torque and the getrag has a decent 5th gear.

The old T5 could not handle the power in 5th gear, the more modern Supra Gearboxes were not available at the time, the bottom 4 gear ratios of the Getrag are almost the same as the jag 4 speed and most importantly the gearbox is short and doesn't have a long tailshaft housing with the gearshift inbuilt - the gearshift is not part gearbox housing which is important in a jag as the gearshift sits right up near the bell housing. Likewise the holden V8 at the time only produced about 10kw less than the jag but a lot more torque so the gearbox is able to handle what the jag had on offer. Its biggest downside is that the bell housing is part of the gearbox housing.

For sure if I was doing it now - I would look at other options but at the time there was not much available that could handle the power at a reasonable price. The box came from HSV and was pulled out of a Holden being converted into a HSV where they pulled out the new gearboxes and put in Hollingers.

I wouldn't mind putting in a 6speed but the holden V8 with its torque has problem pulling it in 6th gear and any reasonable speed so I doubt the lower torqued V12 would be able to pull 6th gear reasonably at anything resembling legal speed.

Cheers

Garry

I like your theory and i wish you luck:angel:

still id send a pm to moose:cool:

or jump on that ls1 forum if you can get thru all the big heads and chest beating

[BigJon]

I fitted a Tremec (proper original one, not their version of the T5) to my injected WB. I thought it was a beautiful box, 5th gear was pretty tall though (0.68 to 1 from memory). The engine was putting out somewhere in the region of 300 kw, with torque to match and I never had a drama. All manner of bellhousings are available and the shifter location is optional too. Mal Wood sourced all the bits for me and freighted to Adelaide.

[moose]

Don't bother pm'ing me, coz I don't know!:D

However there is plenty of info on all sorts of stuff on http://www.ls1.com.au as rangieman said.

You didn't ask for opinions, so I won't give you one on the getrag. ;)

[101RRS]

Thanks for the thoughts - I will go on the website - won't mention jag etc - I will just ask the basic question.

The getrag is on the back of the V12, and has been for a number of years but without a speedo - it goes really well - has a nice smooth gear change. I suspect the gearbox better matches the smooth power and lower torque of the V12 as against the lumpy approach of the old 5 litre V8.

Would have loved a Tremec but the $6000 at the time was off the planet. I appreciate the issues with the getrag on the back of the V8 but seems to work better on higher revving lower torque engines.

As I said in 1998 when I did the conversion not much other than a T5 was available.

Thanks

Garry

[awabbit6]

If you have no luck on the forums, my father-in-law is an instrument technician. He does a lot of speedo (Mechanical and Electronic) conversions. Could ask him if you like.

Otherwise, I found this catalogue from the Rod Shop in Vic.
http://www.rodshop.com.au/catalogues/Speedos.pdf
Seems they have alot of ready made solutions.

[101RRS]

Thanks Paul - you have actually answered my question - the top right picture on the web site has a pickup ring gear - the yoke has a special ring on it - the one I used doesn't - I just need this yoke or ring gear.

Thanks

Garry

[awabbit6]

I suspected that you didn't have the yoke . Pleased to help.

[the big fist]

I like your theory and i wish you luck:angel:

still id send a pm to moose:cool:

or jump on that ls1 forum if you can get thru all the big heads and chest beating

*beats chest*

Hey I am a regular on that forum !

[the big fist]

I wouldn't mind putting in a 6speed but the holden V8 with its torque has problem pulling it in 6th gear and any reasonable speed so I doubt the lower torqued V12 would be able to pull 6th gear reasonably at anything resembling legal speed.

Cheers

Garry


I have the T56 in my clubby and with a diff ratio of 3.7 I cruise at about 1600rpm in 6th on the freeway at 100kmh. No problems at all. You just need the right diff gearing for it. A lot of guys run 3.9's and think it is great.

[101RRS]

I have the T56 in my clubby and with a diff ratio of 3.7 I cruise at about 1600rpm in 6th on the freeway at 100kmh. No problems at all. You just need the right diff gearing for it. A lot of guys run 3.9's and think it is great.

Thanks - my comments were based on motoring reports and the experiences of a couple of mates with their SS utes. My jag runs a 3.02 rear diff and at 1600 rpm produces bugger all torque - a 3.9 diff starts to defeat the advantage of having the gearbox.

Cheers

Gazzz

[rangieman]

*beats chest*

Hey I am a regular on that forum !

hehehehe :D i didnt point the finger at any one person:angel: