Guest DISCUS Posted August 26, 2006 Share Posted August 26, 2006 I am installing Quaiffe and CV set-up! Need to choose gear set for the diff. My car currently has LT1 with 325 rw horsepower, torque is solid right accross the rpm band from 2800 to 6500 . The old diff is fine but would prefer the quaiffe. Old diff is R200 3.7 Lsd. Need some help understanding the benefits of going low gearing 3.36 or tall gearing 4.11. The tranny is a Borg Warner T56 with gears as follows first, 3.36 second 2.07, third 1.35, fourth 1.0 fifth .80, sixth .62. One consideration is that currently the tranny has a hum at approx, 1800-2000 rpm when running in sixth at approx 70 mph. When I slip into fifth and the rpm climbs a bit the hum disapears. I like to cruise at about that speed. How much difference will the 4.11 make to your 1/4 mile times as opposed to say the 3.36 diff.? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted August 26, 2006 Share Posted August 26, 2006 If you turn 2000 RPM at 70 mph with your 3.7 rear, then a 4.11 will put you at 2200 while a 3.36 will put you at 1800 RPM for the same mph. Another way to look at is the 4.11 rear in 6th will put you somewhere between 5th and 6th of your current set up. Guess you need to ask yourself how comfortable the car feels at speed with the current gearing, then go up or down from there. I imagine with your engine those would all seem like comfortable RPM's. Next you need to figure out how quickly you have to shift out of first when you are getting on it. Lower gearing will make traction that much harder to control. Quote Link to comment Share on other sites More sharing options...
Guest DISCUS Posted August 26, 2006 Share Posted August 26, 2006 Thanks for your reply! When I am autocrossing I find it necescary to start in second and stay in third! Way too sideways lack of control in first. Find it hard to start quick and controlled as well! So what you say makes sense! I am not out to chase the fastest quarter time, more to improve the handling aspect for autocross! You make a good point, I already avoid first for that reason, thanks again I realize the post was difficult to assess! Sometimes we start considering too many options and need to go back to the basic intention. Quote Link to comment Share on other sites More sharing options...
Guest DISCUS Posted August 27, 2006 Share Posted August 27, 2006 Ok finished my home work with the gear,rpm, mph charts. Had to adjust for the t56 being a newer model so first is 2.97 and sixth is .50 . My numbers are slightly different but the end result is similar. My summary is as follows: Current set-up gives a harmonic hum with the 3.7 at approx 66mph in sixth gear or 1596 rpm. Tires are 225/50 16. t56 is a 1995 camaro style rated for approx 450 ft lb. Change to a 3.36 diff gear would move the harmonic hum theoretically to a higher speed and changing to the 4.11 diff gear should move the harmonic to a lower speed approx 60mph. Seeing as I rarely cruise at 60mph then that should not be an issue and I am more comfortable cruising approx 70 mph where the 4.11 will take me safely out of that harmonic range. Recent dynojet results show best hp increase from 2100 rpm to 4800 rpm then steady to 5800 rpm where limiter is set. Torque is pretty even from 325 to 350 ft.lb. from 1200 rpm right accross to limiter. Engine , tranny and diff should all be well within the limits of the combination. Should not have any problems switching to the 4.11 gears except the further lshortening of first gear. Is that right! Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 28, 2006 Share Posted August 28, 2006 Couldn't you run it in 5th to get the rpms up a little to get out of the harmonic hum range when your speeds are lower? Don't really need to put in 6th if you don't need to. I wouldn't regear the diff if you have a double OD trans and you can get your desired cruise rpms with another OD gear. I would also think that with 225mm tires and your torque, a 4.11 would not be productive or fun in first gear. I would use either a 3.7 or 3.54. If you went with a 3.54 you could get some good $$ for your 3.7 LSD and help offset that Torsen. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 28, 2006 Share Posted August 28, 2006 You might also check with some other autoxers and find out what they think about Quaifes. I'd rather have the clutch style myself. Quote Link to comment Share on other sites More sharing options...
Guest DISCUS Posted August 29, 2006 Share Posted August 29, 2006 Hi Clifton, thanks for the comments, yes I do run in fifth to deal with the harmonics, just thought seeing as I am making a change I could address that issue. First is not overly useful with the 3.7 now , I was thinking more of possible increase in fourth and fifth gears with the change to 4.11. I sure do hope to get a fair price for the 3.7 lsd! Quote Link to comment Share on other sites More sharing options...
Guest DISCUS Posted August 29, 2006 Share Posted August 29, 2006 I appreciate the question, I do not know anyone who has run the quaiffe locally, I am up in Canada, west. Quote Link to comment Share on other sites More sharing options...
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