Jump to content

3.92 diff


westy turbo

Recommended Posts

As a newbie am kinda confused :bangshead: the 3.92 gives a higher speed than a 3.62? which will you recomend for track use,and also if the diff hasnt have that little label on in,how i can regognize which one is it...IF i can :down:
Link to comment
Share on other sites

Hi Westy

A 3.92 diff will give you a lower top speed but improve the acceleration of the car.

If the part# tag is missing the only way to tell is to turn the input shaft and watch the outputs. I would mark one side on the case and output turn the input shaft and count how many revolutions are needed to turn the output around once.

Or if the diff is stripped then you can count the teeth on the pinion and on the crown wheel and then divide the no of teeth on the crown wheel by the no of teeth on the pinion.

Hope this makes it all clear

Richard

Link to comment
Share on other sites

Thanks Richard! you know about how many turns will give the numbur for each(3.62-3.92)
Link to comment
Share on other sites

As a newbie am kinda confused :bangshead: the 3.92 gives a higher speed than a 3.62? which will you recomend for track use,and also if the diff hasnt have that little label on in,how i can regognize which one is it...IF i can :down:

Not sure if Ive just been lucky but Ive always found the ratio written in yellow pen in the crown wheel. Access is fairly easy by removing torx bolts on back of diff. You will need some RTV silicone to re-seal it however.

Before you settle on a diff ratio I would work out what your peak rpm is likely to be along with what size wheels you will be running.

If you are running 15" wheels you shouldn't have a problem but if you go for 13" wheels you may end up with a very low top speed compared to what the car is actually capable of.  

For example Ive got a 3.36 diff with 235x45x13" rears (i.e. small overall diameter) and a T5 gearbox which gives an attainable speed on the road of around 155mph @ 6600rpm.  If I were to fit the 3.92 diff the top speed drops to a rather pathetic 135mph @6600rpm.  

The diff ratio has a big influence on top speed especially when  a turbo motor is unlikely to be pulling as many revs as its gutless normally aspirated cousin.  

All of the above is utter tosh however if you have some fire breathing 500 bhp lump reving to 9000 rpm which I hope you do   :D

Gear Calc is an excellent program for working out what diff ratio will suit you better. Pre-programmed into it are all the gearboxes you are likely to see in a Westfield so it is easy to play with the numbers.

Cheers

Mark

p.s. Best time with the car was when I converted it from NA throttle bodies to the Turbo XE.  Diff ratio was 4.27 with a 4-speed dog box that was 1:1 in 4th. Top speed was 105mph but it did get there very quickly if you could keep the car in a straight line.   :D

Link to comment
Share on other sites

QUOTE
a rather pathetic 135mph @6600rpm.

Some of us can oly dream of such speeds. 129 @ max revs in top using a 3.54 for me :(

If it only revved to 6600 I'd barely be able to break the speed limit :(

What engine / box / wheels are you going for?

Link to comment
Share on other sites

a rather pathetic 135mph @6600rpm.

Some of us can oly dream of such speeds. 129 @ max revs in top using a 3.54 for me :(

If it only revved to 6600 I'd barely be able to break the speed limit :(

What engine / box / wheels are you going for?

sorry forgot to write...its gonna be a drysumped let with MBE 967,T5 box and 7x15 and rear 8x15

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

Please review our Terms of Use, Guidelines and Privacy Policy. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.