without lifting up my 335. What are the chances that i have a 4.10 lsd in it? I am at 4k going 78mph. and first gear is useless but second hold on! The car also has a distinctive whine to the gearing. It has a close ratio 5sp.and a m90 engine so. I don't know if its just the tach maybe they never changed it to a 6 cylinder. let me know


jim

Hey come on guys. Anybody know anything? layne? hello? :help

This is the sort of thing that can be figured out with about 5 minutes of research. I did not know the answer to you question, but used all the tools that you have at your disposal to figure it out for you.

According to Metric Mechanic, the 6 cyl close ratio gear box is the 262 with gear ratios of 3.717, 2.403, 1.776, 1.263, and 1.000. This tranny is usually paired with a 3.07 diff.

Enter your tire size, gear ratios, and see what gear ratio matches the speed you're seeing.

http://www.f-body.org/gears/

Assuming you're running a 205/50 r 15, I figure you have a 3.64 rear end which says you should be running 75 mph at 4000 rpm.

If you do get under the car, there will be a tag hanging off the diff cover that should list it as a 4.10 or 3.91. It should also list the number of pinion gear teeth and ring gear teeth. Divide the larger number by the smaller number and it should give you the ratio.

Or, get the back wheels off the ground enough to spin them. Count the number of drive shaft rotations vs. wheel rotations. if its a 4.10, the drive shaft should spin 4.1 times for every complete rotation of the wheels.

thanks that will help. any idea about the the old tach.i think some one said that if they diddnt change it. it would run at 33% higher.

Correct, it would read 33% higher since it would see 6 ignition pulses instead of the 4 its looking for.

I doubt they would have done a 6 cyl conversion without swapping tachs. If you did happen to have a 4 cyl tach right now, 33% of 4000 would be 1320 rpms. That would mean the motor would be turning an actual rpm of around 2700 at 80 mph, which would mean your diff would have to be somewhere around a 2.3 which is highly, highly unlikely so rule that out as a posibility.

Both the 3.64 and the 3.45 are factory e21 diffs, if its not those 2 you either have a larger diff out of a 5er or something custom. If you plug the 3.45 in you should be doing 80 at 4000 rpm, so that may be more likely.

You could see a difference of 2 mph with just swapping to a different brand of tire in the same size or swapping from the stock 185/70r13 to a 205/50 r15.

Why do you think there's an issue? With the close ratio box you don't have overdrive, 4000 rpm would be normal at 80mph with a 3.45 diff. With the 3.5 m30 in a 2500 lb car, 1st gear should be useless. I would have thought 2nd would be near useless for you as well. In my car, 1st is useless and I have wheel spin in 2nd.

i bought this car off a guy who has owned since the 80s. i am pretty educated with bmw engines except this one. its a 3.5 m90. euro so i am in the dark. not to metion it is carburated. i am not used to the gearing I don't want to blow anything up. going 80mph I feel i sould have a 6th gear. but my other car is 535is, witch the gearing is a lot different so maybe it will take some time to get used to. this car has surrvived this long the way it is. so i guess I will just role with it. yes ,first and second are useless. The rest are fast as hell 4th to 5th are insane. terry hall built this car. and he knows what he is doing . he built The Hitman. and those 635 funny cars.

If this is a Dietel car I blieve that they used the e12 diff.

no this is a Hall engineering car. but looking up dietel, I wish it was 345i :D

Dietel did a few 335's IIRC.

I dont know HALL engineering was all i was told and then I spoke with terry hall, he said it was a long time ago but he modded it to beat the h35.and the thing moved like hell. witch it does:devillook

Why not get a pic of the diff? Maybe they did change it for a beefier one. It would make no sense at all to have a 4.10, that kind of ratio is to make up for a lack of power (which I don't think you have). Something in the low 3 range should be nice, you might consider changing it, but thats going to depend on what is installed.

ill snap a pic tomorrow