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[gstylebaby]

Hi All,
Can i ask which is the better diff to have 3.7 or the 3.9 lsd ?? or what is the difference between the two as i know nothing about diff's lol.

[aaronjb]

That depends what you want from it.. the 3.9 is a shorter ratio (longer numerically) which means more acceleration but higher revs for any given speed, the 3.7 is slightly longer ratio (shorter numerically) which means slightly less acceleration but lower revs for any given speed..

So what do you want, acceleration or lower cruising RPM?

As for LSD .. you don't really "need" an LSD in the Omega unless you're planning on taking it on track and/or driving like TheBoy a loon IMHO, anyway.

[feeutfo]

4.2

[feeutfo]

Although I'm talking for a 3.2.

Haven't looked into the, er, <cough>"lighter"<cough> engined variants.

[serek]

4.2

if you have 3.0 or 3.2 with auto box thats its best option 

[gstylebaby]

So why is 4.2 the best one to have then fellas or do you mean the 4.2 is the lsd or are there different lsd as well. I looking into what to replace the hummy one on my estate with it has 3.7 one at the mo so not sure what to do....

[Kevin Wood]

The question is what you want to achieve by changing the ratio. If you're happy with the current gearing, then 3.7 is your answer.

Before considering a change, we need to know what engine and gearbox you have. If your 3.7 diff is standard, then I'm guessing it's probably a 3.0 manual, in which case, you'll find a 4.22 diff pretty tiresome IMHO because the manual box is geared shorter than the automatic.

Read this FAQ to see what effect the various diffs will have: http://www.omegaowners.com/forum/index.php?topic=90497.0

As regards an LSD, again, what do you want to achieve?

For road use, about the only advantage, IMHO, is that it will give you better traction out of a T junction when the inside wheel tends to slip and then only when traction control is off as that usually has cut in by then and stopped play. Downside is that it can make the car more prone to step out at the back end which might actually mean you end up taking it more easy in places, especially on wet roundabouts.

LSDs are rare, and only available in a couple of ratios. Whilst you can get them rebuilt with the CW&P from another diff to choose the ratio, that's a skilled and potentially expensive job. 2nd hand LSDs are likely to have a lot of miles on them these days, so might be worn, requiring an overhaul for best performance. Again, an expensive business.

You'd need to be sure it's a mod you want to do before going to the trouble, IMHO.

[zirk]

In my experience most plod forces that fitted LSD, had the correct ratio for Autos and Manuals to bring it in line with a standard setup, although a few Forces did fit different ratios presumable to gain acceleration over standard, although having driven a few now I cant honestly say it improves acceleration, certainly feels strange doing 70mph at just over 3000rpm in top though.

Agreed, dont really need LSD, unless track or drifting is in mind, having said that LSD is handy though, last xmas when we had the snow, had to pick someone who was stranded, the Elite Auto couldn't get up the Hill, so spun around and got the 3.2 Manual, no probs at all, quiet funny really seeing all the Mercs and BM's stuck half way up, OK so its not the same as a proper 4X4, but saved the day for me on that occasion.