Quick diff question

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Paul02

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Will the diff from my 3.0 cs auto work with a 3.5 with 5-speed manual .
Not sure of ratio as diff not here ,
Cheers Paul
 
Paul,

the answer depends on which 5 speed you have. if it is a close ratio (dogleg box - 1st is down and to the left) or the overdrive box (1st is up and to the left). if you have the overdrive box, everything will be fine with your standard diff. it will work ok with the close ratio box, your revs will just be higher.

good luck with the tranny swap. happy holidays
scott
 
Paul02 said:
Will the diff from my 3.0 cs auto work with a 3.5 with 5-speed manual .
Not sure of ratio as diff not here ,
Cheers Paul
Click to expand...

Odds favor an auto 3.0 being originally equipped with a 3.64/1 rear drive gearing. With wide ratio overdrive and the additional torque produced by a larger displacement engine, the combo would be practical in everyday driving including long autobahn stretches.

Of course - assumptions can be wrong since there is hardly any control over special orders or modifications by prior owners. You can determine what you have by counting teeth on ring and pinion gears, or looking for markings on differential case, or comparing drive shaft rotation to half-shaft/tire rotation. Transmission gearing can be narrowed down by shift pattern, model number, and/or by comparing input rotations to output rotations in each gear.

Lots more in archives.

148_0208_gear_1_z.jpg

http://www.chevyhiperformance.com/techarticles/148_0208_gear_ratio_calculating/viewall.html
 
I'm having a real blonde moment here chaps, can someone explain how the lock up percentage works on a bmw LSD? I see LSD diffs for sale and its either a 25% lock up, or a 75% lock up, how does this work...!
??????....

And the LSD I'm putting in is out of the M6 E24, the ratio is 3.07, i should be able to light the tyres up and leave 11's still won't I, or is that ratio to high?? I'm after a ratio that will be rapid through the gears. What's the best to get??










And after all these years, I still struggle to understand how a bloody clutch works!!......honest!!:neutral:
 
Even a 3.25 is not enough unless you live a block from the autobahn.
For a od tranny you need a 11/38 or a 11/40.
 
The percent lock up is percent of torque transferred to the wheel with the most traction. That means if the wheel with the least traction is being driven with 40 ft-lbs the wheel with the most traction will have 10 ft-lbs to drive it if you have a 25% LSD. That also means if one tire is on ice (or is in the air) and it takes near zero torque to drive it, the other wheel gets zero torque.
 
gwittman said:
The percent lock up is percent of torque transferred to the wheel with the most traction. That means if the wheel with the least traction is being driven with 40 ft-lbs the wheel with the most traction will have 10 ft-lbs to drive it if you have a 25% LSD. That also means if one tire is on ice (or is in the air) and it takes near zero torque to drive it, the other wheel gets zero torque.
Click to expand...

So what's better, high percentage or low percentage?
 
mr bump said:
So what's better, high percentage or low percentage?
Click to expand...

Depends on your typical driving conditions. If you were to weld the differential and lock it for 100% torque to both wheels - all of the time (as is often done in certain racing applications) you would eat up your tires under normal street driving conditions. "Fishtailing" and more difficult to control handling might also result on the street - whenever you lose traction. From memory, the factory-offered stock lockup percentage was 25%. Higher percentages were available via special order - mostly because the vast majority of E9s were designed for street use rather than rallying.

http://www.drivingfast.net/technology/differentials.htm
 
I am pretty sure the 3.0 CS LSD was 25% but the 2800 CS was higher. I think it was around 45%. I like a higher % LSD but care needs to be taken on the street. The inside tire is easier to chirp or momentarily brake loose when accelerating from a stop and going around a sharp corner. When the street is wet, powering around a corner can result in total loss of traction in the rear. This can bring around the rear quickly if you don't let up on the 'go' pedal immediately.

The advantage of having a higher % LSD is when taking corners at high speeds under power, you will be less likely to spin the inside rear tire as its weight is unloaded on it due to the roll of the car. This means you can accelerate better out of a high speed corner with a high % LSD. As noted by nashvillecat, it all depends on you driving habits.
 
the later style diffs that came in M6's will not bolt into an earlier car
you would need to modify your subframe or install one from a latter car
early cars have whats called a side loader while the later cars have the "rear loader" what that means is the access panel to the guts is on the side or the rear, most cars after 82 are rear loaders
and the factory lock up on those cars I believe to 25%
only modified LSD units have higher lock up %, Personally I pay more attention to how many clutches the unit has and what the ramp angle's are
the factory units all come with 2 disc's
 
bdigel said:
the later style diffs that came in M6's will not bolt into an earlier car
you would need to modify your subframe or install one from a latter car
early cars have whats called a side loader while the later cars have the "rear loader" what that means is the access panel to the guts is on the side or the rear, most cars after 82 are rear loaders
and the factory lock up on those cars I believe to 25%
only modified LSD units have higher lock up %, Personally I pay more attention to how many clutches the unit has and what the ramp angle's are
the factory units all come with 2 disc's
Click to expand...

When racing F2 stock cars, I tried to get used to a LSD, but in the end I welded the diff up, but that's not an option with this car. The diff I'm putting in is a side loader, I'm just putting the cwp and LSD unit.
 
3.45 with OD 5-speed box

This is a very good combo for most driving situations. 3.64 will make you want another gear on the motorway/freeway/autobahn, even though you will smile on take off at the redlights.
I have one car with 3.25 and the OD box. Very comfortable for longer drives.
I have 3.15 with OD on one car which has the 3.5 L engine. Super quiet on the motorway.
I have one with 3.07 and CR box, just like the 635 CSi. You want the 3.5L engine here.
40% LS is ideal in my view. They tend to wear down with useage.
As changing the diff is a 2 hr job, you can easily change if not satisfied. The minimal inaccuracy on the speedo is ok, if you cannot be bothered to do the work needed.
 
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