mg axle ratios

[Roger King]

I have a Jag Powr-lok 3.54 in my sbf-powered car, same ratio as the original street 289. Works very well, although that's with a T5 'box with 0.68 overdrive.

Roger

[greenmachine]

You are right Dave, it is a specialised job. The crown wheel and pinion and planet gears are mounted in the axle housing with a access plate on the back. Hardy engineering will carry out the machining and fitting plus supply the new crown wheel etc for approx £ 500.00. All I now need to do is tke the axle to them minus the brake back plates, half shafts and brake lines.
If anybody would like to borrow a puller for the half shafts, please e mail me as I have one.


Keith

[clive]

Clive with a SBC

[David Large]

I see I am mixing post submitted by Keith and Peter but Clive what diff ratio are you running?

DL

[petercharman]

David

Never thought about checking what TVR run on their rear axel.

What I have found out is that there final drive on 5.00L chimeara/griffiths are 3.31 and there top gear ratio is 0.8

My gearbox is a 5 speed LT77 I have a listing somewhere of the ratios of that box, but can't put my hands on it at the moment, anyone know what they are or could ponit me to the right web site.

From the threads above I am right to assume that only the crown wheel needs to be changed ? rather than the whole diff to achieve a different final drive ratio. Not that it's any easier, still a specialist job.

Peter

[David Large]

On an MGB diff you need to change the crown wheel & pinion, bearings, shims, oil seals. The crown wheel & pinion sit in a carrier, that may need to be changed or modified. Definitely a specialist job. I have a feeling (but not sure why) that 5th gear on an LT77 is 1:1...............but needs checking.

I am not an expert on all of this, just been through it.

David

[Tony 289]

When I built mine in 1984, I used a Sherpa van pinion and crownwheel. The diff ratio is 3.33 and works well. The pinion gear was wider than the original so I had 1/8" milled out of the crown wheel and 1/16" turned off the carrier. 70 mph @ 2500 revs with a LT77 box (seen the remarks) However, I give the transmission quite a bit of abuse and it has never broken, see me out drag a 427 and get off the line quicker than a Skyline http://www.youtube.com/watch?v=dpQu9X0Yxg4 and http://www.youtube.com/watch?v=mKalpx-Te_4

[v8bassman]

When I built mine in 1984, I used a Sherpa van pinion and crownwheel. The diff ratio is 3.33 and works well. The pinion gear was wider than the original so I had 1/8" milled out of the crown wheel and 1/16" turned off the carrier. 70 mph @ 2500 revs with a LT77 box (seen the remarks) However, I give the transmission quite a bit of abuse and it has never broken, see me out drag a 427 and get off the line quicker than a Skyline http://www.youtube.com/watch?v=dpQu9X0Yxg4 and http://www.youtube.com/watch?v=mKalpx-Te_4

Hey Tony,
When you handed me the keys at Le Mans last year and told me to take it for a spin, I didnt realise what a demon machine it would be my privilege to drive. Thanks mate!

[Wynterburne]

Hi

Just for interest, if you log onto the Members section and go to "Technical Information" and under "Gearbox, Clutch and Axle" heading you will find a Gear Ratio Calculator.

It allows you to compare two sets of data on Tyre size, gear ratios and axle ratio. It provides speeds at specified rpm which can also be amended.

May be of interest to see what changing ratios etc can do.

Regards

Richard

PS - if you cannot remember the log-on you will have to email me!

[Tony 289]

Hi Dave

Was a pleasure, glad you did not drive it like I do. fab time in LeMans, hope the build is going well, hope to see you at Silverstone.