RS41 crown diff swap

[Casino Kid]

hi Ive just finished my 18rg/w50 conversion in to a 1965 crown and on my first test drive i have noticed that the diff ratio is short, meaning to do a 100kph i think it will be screaming its head off. so does anyone know of a bolt in diff center swap that would make it nice to drive

[Wildsupra]

hi Ive just finished my 18rg/w50 conversion

cool so we will be seeing it on the cruise today then


Someone please find this man a diff!!! cruising through the suburbs at 40k's in 4th was no fun!!

[roadsailing]

whats your final drive ratio?

if you know wat RPM it will do with a certain diff, then the new RPM will be proportional to the diffecence in ratio.

ie if you start with a 3.9 and go to a 4.1, the new RPM will be 4.1/3.0 higher

HTH

[gianttomato]

It'll be an E series diff. I suspect you'll have either 4.375:1 or 4.875:1 drive ratio, but it would be worth your while checking. What gearbox was your RS41 originally equipped with - 3 speed, 3 speed with electric overdrive or 4 speed? This will help us work out what diff ratio you have.

Get a diff from an MX32 or an MX62 - they should have an E series diff with a 3.9:1 ratio. I'm not aware of any easily available E series diffs with a taller ratio - perhaps others could chime in?

[rob_85]

he had 3spd with elec overdrive

[Casino Kid]

ah ok it was a 3spd with the elec overdrive. I got a crown manual but I cant find the ratio anywhere in it. All it says is that a RS41 diff is ment to hav the following spec

Drive pinion; 8 teeth
Ring gear; 39
diff pinion;16
diff side gear;10

Dose that help at all

[Wildsupra]

too easy dude.

Ring gear divided by drive pinion

39/8 = 4.875

if you can find a 3.9 that will be ample dude.

[gianttomato]

You have a 4.875:1 diff, which blows goats.

Fit the Cressida diff I mentioned - you'll be pretty happy with that.

[kingmick]

You have a 4.875:1 diff, because i blow goats.

Fit the Cressida diff I mentioned - you'll be pretty happy with that.

A 4.8 is very high as i have never used over a 4.55 for anything. 4.8 might be great for hillclimbs but it would suck for day to day cruise rev's.
Of the mark a 4.8 would work wonders for cars with no horsepower, but for anything with horsepower it will spin in 4th with the foot down.

What you have to choose between is "of the line, top end or cruise".If you do long distance driving most of the time, bring the cruise rev's down. If you want top end for the track lower the diff ratio. If you want of the mark speed, just look at what you have now and lower the ratio if its still spinning in 5th with 120hp or so!

[Casino Kid]

yeah well the car is a pure cruiser So i dont realy care that much about of the line go so hopefully the cress diff will be perfect