what would a 4.10 do to my M20?

[scumtrash]

i just bought my first e30 (1988 325is) and i am running everything stock other then my exhaust and a mark D chip. now i know with the chip i can rev 500 rpms higher in each gear. i just bought a 4.10 LSD diff for 100 dollars just because it was a good deal and i am considering replacing my current diff with the 4.10. if i replace my current stock diff with a 4.10 i will get better acceleration correct?
and it will also raise my rpms 500 right?

what im really trying to figure out is will putting the 4.10 raise my rpms a full 1000? and is that dangerous for my engine?

[NeedaE30]

make it uncomfortable for highway driving and ruin your 5th gear MPG.. 4.10's are best suited for auto x

a differential does not increase your rpms a differential determines where your rpms sit at any given speed

so say you were at 2,500 rpms at 60mph with whatever diff you have. Then change it to a higher numerical ratio diff you could be at 3,000 rpms at 60mph this is just an example and not based on any data or specific differential

[scumtrash]

why would it make it uncomfortable for highway driving?

[NeedaE30]

well, maybe not for some or most people.. but when i drive on the highway and i'm not trying to be speed racer.. i like my rpms to be as low as possible at the highest speed possible for a quieter ride, more gas mileage and less engine wear.. but i guess i could just be talking out of my ass so you should just ignore both of these posts ;)

[JinormusJ]

Post above is correct

A 4.10 will FEEL faster because there are less revs per gear due to having a taller ratio. So, I don't know where you're getting your information from, but it will make your cruising speed at 65 and 80 in 5th jump from 3450 to 3750 due to the shorter gears.

It won't push your rev-limited higher if that's what your asking. All a chip does is release the stock rev-governor and replace it with an aftermarket limiter. (AKA, increasing your redline from 6500 to 7000 etc.) This wont increase your revs in any range, rather, it will change when the rev-limiter kicks in and cuts fuel to the engine at a certain max RPM. So, instead of cutting fuel and "bumping redline" at 6500, a chip will allow the governor to rev passed that and "bump redline" at 7000 instead

A differential has nothing to do with the electronics/ECU in an e30 and will not modify your rev-limiter.


Knowing that, highway driving WILL be uncomfortable to most people, as most people would like to keep their revs slow 3500 for 80MPH for less engine wear, ride comfort, and low sound

[NeedaE30]

A Camshaft and appropriate tune i believe are what can increase your actual RPMS

[EatsHondas]

I have a 4.10 mated to a G260. Even though 5th is overdriven, it takes 3k RPM to let me cruise at 65. I also have undersize tires, so I'm probably going 58-60 mph. Damn quick when you're not on the highway, but you run out of legs so fast - as soon as you get comfortable in the powerband, it's time for another gear. 1st is pretty much a granny gear.

[scumtrash]

ok cool, im getting 90% of this info from other forums and the rest from an old guy i know who used to race e30s. none of which i want to quote as fact. but just to be clear, a 4.10 would just shorten the gears meaning higher revs meaning my mpgs are going to be lower and it will be louder. but it will also boost my acceleration?

is there a better way to boost my acceleration off the line?

would the 4.10 cause more wear on the timing belt or were you just suggesting that as good maintenance?

[NeedaE30]

it will turn 1st gear almost useless when trying to drag race.. it will lower your top speed and ruin your mpg at speed. supercharge it if you want to boost acceleration off the line...

[JinormusJ]

It won't increase wear to a timing belt. Really it doesn't do anything than add an increased wear to a ratio of about 200-300 extra revs per mile, which.. Is really non-existent. Some manual e30s were equipped with 4.10 LSDs from the factory (mostly verts, to help push all that extra weight around).

All a 4.10 will do is shorten your gear ratio, meaning less MPGs, louder ride because you are in a higher rev range per MPH, and your acceleration will be slightly faster. Be prepared to drop 2-3 MPGs, even more on street. Personally, I am against 4.10 in a manual Getrag coupe/sedan. There isn't any point to sacrifice that MPG for a borderline insignificant increase in acceleration


If you want a fast car, build a fast motor

[Danny]

It may or may not give it at least or as much as 50 more horsepowers.

[scumtrash]

It may or may not give it at least or as much as 50 more horsepowers.

what factors would go in to the 50+ horsepower?

[JinormusJ]

Horsepowers :nice:

[fanboi]

what factors would go in to the 50+ horsepower?

Oh no....

Poor kid

[scumtrash]

in all my ignorance level with me and explain to me what i missed?