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diff R&P swap question


M3M3

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started the project to change from 3.91 Ring and pinion to 4.44 today.

questions for you experts..

on the pinion...there are apparently two kind of splines. pic below shows the pinion from a 72 diff with course splines for input flange. pinion on right is from small case e30 diff. it has fine splines for the input flange.

2012-12-08_16-01-59_633.jpg

2012-12-08_16-02-04_164.jpg

when did they change the splines on the 166 diffs? the dust cap on the flange needs to be different as the nose of the 02 case, e21 case and e30 cases are different sizes.

i did find this in a search, but it was not complete.

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,222161/highlight,diff+input+flange+spline/

second question.

the spacer inside the inner bearing set. i assume that stays with the case when changing R&P? the two pinions are identical in all the measurements i took, so it appears the spacer inside the inner bearing is to account for case production variance?

thanks!

2xM3

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All I know is, I hope you have a good relationship with the local constabulary. Because that's going to be too much fun.

;-)

Ray

Stop reading this! Don't you have anything better to do?? :P
Two running things. Two broken things.

 

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oddly enough, the final gearing in top gear with e21 5spd and 4.44 diff is nearly identical to a stock 4spd tranny and stock 3.64 diff. top speed at 7500 rpm will be limited to 138mph though....LOL...

1st gear will be kinda low, but 3/4/5 are much closer together and should optimize accel and shift points at Summit Point track.....:-)

2xM3

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The spacer stays with the pinion, to correct for the +- number etched in its nose.

At least, that's what I've found. Ideally, you set it up and check it to see if

it's running at the right depths, since the cases probably vary, too.

Ok, that pinion nose is odd. I've done about a half- dozen, going from

E30 and E36 r&p's into E21 cases and never had that problem.

And yeah, that larger round flange looks E36, but maybe late E30 too.

But what I think is that the coarse spline's a 2002- only thing,

'cause I've always been able to use the 'eared' flange that works better

with a 2002 driveshaft. I had to toss most of my 'remainder' parts,

but I think you might need an E21 flange....

fwiw,

t

ps, 4.44 is pretty pointless on the street. Good on the track, though,

with the 5- speed for longer tracks on taller tires.

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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ahhhh! was wondering what the + number on the pinion nose was.

diff i am swapping the gearset into is an e21 3.91, so hopefully has the fine splines on its flange. did not want to take that one apart until i had all the variables figured out.

correct, this is not for the street. track only mod! based on my data from using a 3.91 and a 4.10 at Summit Point, the 4.44 moves all the shift points to the right spot and keeps the S14 up in the power band on corner exit. the gearbox stays in the 3/4/5 close range. basically a band-aid for not having a CR gearbox.

thanks T!

2xM3

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Yup, your gearing calcs match what I found- 2nd is now only for rolling

start launches, and 3-4-3-4-3 seems to get you around most tracks,

with 5th for the straights.

This with the overdrive 5 and the 4.44.

Driveline balance and alignment gets a lot more important, as the driveshaft spins

damn near 10k rpm at redline...

It IS nice to be able to paddock crawl in first.

t

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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yeah, it's funny- I JUST got a bite on it when I did the 4.44's- the 4.56's

are probably completely impossible.

Is there a 4.56?

t

clearly I need a better bearing puller. the HF thing i have has no decent edge on it to get under that race.

what are you saying Ray? that i can't just leave something alone? that i must constantly fiddle with the car? LOL...guilty.

2xM3

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Here's something else to tempt you Marshall.

5.30

530gearset.jpg

Correct me if I am wrong, but I recall that numerically higher diff ratio R&P sets are weaker than the lower ratio R&P's. So a 4.56 R&P would be weaker than a 3.64. This goes back to my 4x4 days. Not sure about the BMW ones.

Jim Gerock

 

Riviera 69 2002 built 5/30/69 "Oscar"

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Correct me if I am wrong, but I recall that numerically higher diff ratio R&P sets are weaker than the lower ratio R&P's. So a 4.56 R&P would be weaker than a 3.64. This goes back to my 4x4 days. Not sure about the BMW ones.

Frankly, I don't know. I suppose its technically possible based on gear shape. BMW Motorsport offered ring/pinions in increments up to a 6:1 ratio. I'm assuming these were equipped on some alpina and other period cars.

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