12 replies to this topic

[Ricky Bobby]

Hi,

I'm doing an LS1, T56 conversion for my hatch back. I will be using 14" 50 series tyres

and am about to order a nine inch diff. Can anyone recommend a diff ratio that would suit a power cruising style of car?

I'm in Hobart and was thinking of using Chris's differential services (Melb). I haven't spoken to him yet and would like to go to him with some recommendations. Or can anyone recommend another supplier?

Thanks.

[myss427]

With the .6 overdrive with 3.91 and 25.5inch rolling diameter you can get 1800revs at 100Kph, thats what mine does.

Edited by myss427, 05 March 2016 - 12:19 PM.

[ls2lxhatch]

Once you have confirmed what ratios are in the T56 use Gearcalc to compare diff ratios.

 

http://locost7.info/gearcalc.php

[MARKL]

Once you have confirmed what ratios are in the T56 use Gearcalc to compare diff ratios.

 

http://locost7.info/gearcalc.php

Thanks for that! I know there are others but that one is quick and easy to use. I have been undecided about what diff ratio to go with for ages and that one made it super easy.

 

Taller tyre, VS T56 + 4.11 diff = 1,700rpm at 100km/h which is perfect in my book.

Edited by MARKL, 11 March 2016 - 04:48 PM.

[ls2lxhatch]

This table will give you a rough idea of how your ratios compare. I guessed you plan to run a 25.5 tyre based on 1700 rpm at 100 km/h.
 


https://en.wikipedia...56_transmission

[MARKL]

Cheers. The 1st and 6th gear ratios are the same as my understanding. The engine for now will be a fairly stock injected 304, as much as I would like to go nuts with the engine the car is being built as a cruiser more than anything else. 4.11 seems a reasonable compromise for getting off the line a little better and reasonable cruising.

 

Every time I look at modding the 304 in any substantial way I come to the same conclusion you guys have, that an LS motor is better value. Anyhow I will worry about that later I ned to get the car moving again...

[neglectedtorana]

When I was buying bits Mal Wood recommended changing 5/6th from the .75 and .5 to higher ratios. I think the numbers were .85 and .75

Was not going to be cheap but sounds like a good idea to have 6 ratios closer together

[MARKL]

There are different ratios, including 1st and 6th. Some are .65 for 6th gear. Mine is .5

Yes, the numbers that LS2LXhatch put up agreed with my research for my T56 from a VS.

[ls2lxhatch]

The wiki link below the table lists the ratios and Tag Ids for 39 T56 applications (including Commodore). According to the table there are four different 6th gear ratios and four different 1st gear ratios.

Based on the table I guess MYSS427 has a T56 Chevy Magnum which has a 0.63 top gear.
https://en.wikipedia...56_transmission

Edited by ls2lxhatch, 13 March 2016 - 11:40 PM.

[gtrboyy]

My ol' stock engined vn grp a was horrible 6th gear 110km/h it struggled,..only had 3.4 gears I think iirc where as my m6 vy ss could do it easily on cruise control.

 

Definately should go shorter gears if holden 5l...if ls1 do it anyway they love shorter gearing lol.