Help! Crusing @ 60mph 5th gear 4000 revs

[supkev]

I have a euro cluster and I have a 3.73 lsd, anyone know what might be the problem? everyone thinks I got a 4.10 but thats not the case I went underneath my car and it says 3.73? anyone know what could be the problem?

[Kershaw]

coding plug issue?

[supkev]

Hmm I'll check that out but I highly doubt its that. I lined up with my friends car at 60 mph and it sounds like my car is at 4000 revs.

[A Sucked Orange]

Its either not 4k, or its tiny wheels, or its your diff.

[supkev]

I'm thinking might be my diff, I have stock weaves.

[nando]

there is no diff ratio that would result in 4krpm at 60mph, even with slightly undersized tires.

something else is wrong.

[e30loverSC]

what should it be?

[supkev]

Yea thats what I thought even a 4.10 is like at 3500-3700 I can barely keep up though my car is a stroker I can hit 110 mph but I'd be at 7k or beyond (I have no redline) but the only other thing I can think of is transmission gearing? I'mma change the diff fluid soon see if it helps

[supkev]

Now if I had a 4 banger 318 I would understand but in my I6 hmm I get like 22mpg combined 16-17 city but I know other people with 3.73 are getting better than what I get.

[nando]

a 4.10 is about 3000rpm at 60mph, not 3500-3700. 80mph is about 3750.

[supkev]

Damn what could be the possibilities for my high rev on freeway's :/

[nando]

your tach is probably not reading correctly

[zxert]

I don't think that fluid will have anything to do with it, though changing it is always good. Think about it, a differential is either engaged or it isn't. Fluid or lack of fluid doesn't play a part in RPMs. I honestly think there isn't a problem. It sounds like you have a 4.10 diff with a 3.73 cover. What year and model E30 do you have.



Here are the gear ratios for different models (SEE ATTACHMENT)

Heres a calculator that will tell you RPM. Just input the data for your model and BAM! You're pregnant. I mean, your RPM.
http://www.f-body.org/gears/

I put in the numbers for a 325i 5 speed w/ a 4.10 and got 60mph @ 3100rpm just as nando says.

Post what transmission you have and we can help you.

Also post which differential you had before and RPM at speed with that diff.

[joonsup]

a 4.10 is about 3000rpm at 60mph, not 3500-3700. 80mph is about 3750.

on my 3.73 lsd i'm hitting 3000rpm at around 80mph in my 5 speed stock transmission

[nando]

I'm telling you - there is no way a 4.10 will do 4000rpm at 60mph. Not unless you're running rubber band tires on 13" wheels.

I get 2800rpm at 60mph with 205/55-15 tires (23.9" diameter) and a 4.10 with the .81 G260 5th gear. with my 235s it just a hair lower.

and a 3.73 with stock diameter tires is 3400 at 80, not 3000. people exaggerate a lot.. 4000rpm with stock diameter tires and a 4.10 is over 85mph, not 80mph as many claim.