Differential question

Peter Coomaraswamy

Peter Coomaraswamy

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Hello gurus, I'm remotely helping a friend with a 5-speed conversion and he's having a little trouble with a couple of things, he tells me that since the conversion the car will not go over 80 MPH and was wondering if the differential (pictured below) would have any bearing on that- assuming it's not slipping or the clutch is not slipping. The car is not near me or I would break it myself but any help would be appreciated.

Thanks,

Peter
toms diff.jpg
 
Oh, and another question, is there a particular Giubo/flex disk that I should get for a 2800 CS with the 5 speed conversion. I used to call Ben at LJI and he knew all this stuff in his head and usually had them in stock but he's not there anymore :-(
 
That's a 3.45 LSD. I used the M5 guibo (German part, not chinese) that Don suggested. Much better design than the stock exploding donut.
 
Speedo gear in 5 speed could be wrong and he may be going 110 but only showing 80. Doesn't seem like it would be that far off though. Does the car rev up to redline rpm in the lower gears? Not getting enough fuel?
 
As Sven says - have him check the indication of the speedometer vs a GPS measurement.

If it is a 265/5, the gear takeoff is probably matched to the differntial ratio of the car it was removed from. In MY case, that was a 3.07 diff. So, a 3.45 diff for me would mean The speedometer indication would be about 12% FASTER than the actual vehicle speed. The car had a 3.64 diff in it when I bought it, and the speedometer was 20% higher than the actual speed.

It does sound to me like the clutch may be slipping if the engine is revving higher than 5K rpm.
 
Thanks guys, It would be easier if the car was not 800 miles away, I put him in touch with another member in the VA area so they could beat their heads against a wall together :)
 
Was a new clutch installed during the 5sp swap? I think the most important bit of information that is missing is the engine rpm.
 
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