new gearbox - what do i go for ?

Fri Jul 25, 2008 2:51 pm

my track car box is on its way out. the guy who does my work for me reckons i really shoudl change it before something goes bang big time. problem is i have a dogleg box fitted (??from an M3 ?). i also have an LSD. I didnt convert the car myself so am a bit in the dark about ratios etc.
I dont really need the dogleg box. its a pain remembering which gear you are in and also i never use 1st as its too short. i thin kit was set up for getting good starts off the line when it was raced.
I am thinking that i shoudl simply put a standard 325 box in and have done as it will be cheaper and easier to source. I find with my current box many corners are between gears - in 3rd i hit the limiter mid corner, in 4th i dont quiet get enough acceleration. I almost run of revs in 5th on long straights.
can anyone advise on the suitability of the standard box for track days (i know my diff ratio comes into play - i will try and find makings on the casing tonight). or can you recommend any alternative box.
thanks

Fri Jul 25, 2008 9:39 pm

Diff ratios make a big difference. Sounds like you've got at least a 4.10 in there if you running out of revs. What car have you got? 325? Try dropping to a 3.91 or less.

How bads the box? Dog legs are ideal for racing so could be worth getting reconned and punting it out.

Fri Jul 25, 2008 9:52 pm

its making a whiring noise which stops when you dip the clutch. apparently its a sign of the main bearing on its way out ???? how much will a recon cost me ??
dont want to change the diff as its an LSD and seams to be ok.

Fri Jul 25, 2008 10:02 pm

I'm no mechanic but could it be the clutch bearing? Would be a shame to junk the box for that.

Not sure on recon prices but someone in the techy bit would know.

Fri Jul 25, 2008 10:12 pm

i am told that if the whiring noise stops when you dip the clutch its the box and if the whiring noise stops when you lift the clutch its the clutch release bearing. the guy i use is a BMW specialist with years of experience working for the main dealer so i trust his judgement. did a track day yesterday and it was fine - just worried i will let go during a track day in the future.

Fri Jul 25, 2008 10:17 pm

Yeah your probably right then. As I say I'm no mechanic.

If your cars an ex race car then it's probably had a good ragging over the year's. Try googling for recon boxes and see what comes up.

Fri Jul 25, 2008 10:27 pm

yeah it has been "used " / "abused" . the engine let go big time last year at croft. "days of thunder" white cloud of smoke moment. one of the pistons ended up being a small ball of metal inside the cylinder. looked like solidified lava !!! i dare say that was a product of its previous life !!! i put in a box standard engine and just changed the cam and put in an E3zone chip. its runs really well. maybe its time for a new box !!

Fri Jul 25, 2008 11:56 pm

Sport close ratio box?

Sun Jul 27, 2008 10:16 am

oze30 - what are you saying ? are you asking if my box is a sport close ratio box or are you suggesting this might be the best option for me ?

Sun Jul 27, 2008 10:24 am

i would say standard box is good as any, the sport box is only close ratio in the first 3 gears and the same as the other box in 4th and 5th

Mon Jul 28, 2008 7:40 am

Holinger RD6-H for the win!

Mon Jul 28, 2008 11:45 am

If you want a cheap close ratio box get a 320i box, they are closer ratio than the standard 325i box.

You will also need the prop shaft though.

Mon Jul 28, 2008 12:03 pm

sorry if this is a silly question - what practical advantage will i notice with the close ratio box. bearing in mind the torque of the 6 pot engine is it necessary to have close ratio. i am not racing - just track day fun. changing the propshaft sounds like a whol load of hassle to me - will it fit the LSD i have as well ? maybe a std box for now and if i dont liek it i can change in the future.

Mon Jul 28, 2008 12:53 pm

Changing the propshaft is like an extra 3 bolts, you have to take most of it off to get the box off anyway.

I have a standrd 325i box in mine and i really notice it bog down when i hit 3rd because of the large jump the stanadard 325i box has between second and third.

with a closer ratio box the gear ratios are close together so there is less of a jump in gearing from the top of one gear to the next.

In other words it makes you faster!

What you may notice if you put a standard 2.5 box in is your car will get slower.....

Mon Jul 28, 2008 1:23 pm

mmm. food for thought. i guess my car is different due to the LSD - i have no idea of the diff ratio. i will try and see if i can see any markings on the casing. if i get a 320 box and propshaft will it fit my diff - ie is the back end of the prop shaft the same ?

Mon Jul 28, 2008 1:24 pm

what is your car though?

is it a 325? 323? etc etc

Mon Jul 28, 2008 6:36 pm

If you want to play with gearbox and diff settings down load the diff calculator from here.

http://www.diffsonline.com/techinfo/index.shtml

If your attached to your gearbox this place specialises in recon getrags.

http://www.bmw-gearboxes.co.uk/

Fri Aug 01, 2008 11:48 am

car is a 325
box is dogleg. markings imply it is a getrag 242 but i dont think this exists. i wonder if is a getrag 262 (dog leg fited to the 323 and the guy who took down the markings for me whilst it was up on his ramps made a mistake / couldnt read the numbers ?).

Fri Aug 01, 2008 12:00 pm

update :
aparently there is such a thing as getrag 242. its very similar to the 262 for the "user" but is internally different. the guy at "all gears" (thanks to shorty73 for the link..bmw-gearboxes.co.uk) was really helpful and gave me lots of advice.
think i will go for the tech1 sport box as a " refresh recon" on my box will be £350 and full rebuild will be £700