2015 STU Discussion!
Jun 15, 2015, 09:45 AM
#168
The breakaway torque on my re-stacked rear differential came down a bit after break-in, but it was still higher than I was comfortable with. My car was still chirping and clunking excessively during any low-speed turns.
I bought a cheap replacement LSD locally, re-stacked it, and put it on the car. Same method, but this diff is substantially quieter and more well-behaved. I just hope it behaves the same under autocross conditions, because my next even is the Utah match tour and I won't have a chance to practice before then.
I think I'll send the old diff in to TRE or Shep and have them do a proper stock rebuild on it. They must have plenty of stock LSD plates lying around after doing so many 12-plate builds, so hopefully they can get the 8-plate diff set up just right for me.
I bought a cheap replacement LSD locally, re-stacked it, and put it on the car. Same method, but this diff is substantially quieter and more well-behaved. I just hope it behaves the same under autocross conditions, because my next even is the Utah match tour and I won't have a chance to practice before then.
I think I'll send the old diff in to TRE or Shep and have them do a proper stock rebuild on it. They must have plenty of stock LSD plates lying around after doing so many 12-plate builds, so hopefully they can get the 8-plate diff set up just right for me.
Jun 15, 2015, 11:24 AM
#169
The breakaway torque on my re-stacked rear differential came down a bit after break-in, but it was still higher than I was comfortable with. My car was still chirping and clunking excessively during any low-speed turns.
I bought a cheap replacement LSD locally, re-stacked it, and put it on the car. Same method, but this diff is substantially quieter and more well-behaved. I just hope it behaves the same under autocross conditions, because my next even is the Utah match tour and I won't have a chance to practice before then.
I think I'll send the old diff in to TRE or Shep and have them do a proper stock rebuild on it. They must have plenty of stock LSD plates lying around after doing so many 12-plate builds, so hopefully they can get the 8-plate diff set up just right for me.
I bought a cheap replacement LSD locally, re-stacked it, and put it on the car. Same method, but this diff is substantially quieter and more well-behaved. I just hope it behaves the same under autocross conditions, because my next even is the Utah match tour and I won't have a chance to practice before then.
I think I'll send the old diff in to TRE or Shep and have them do a proper stock rebuild on it. They must have plenty of stock LSD plates lying around after doing so many 12-plate builds, so hopefully they can get the 8-plate diff set up just right for me.
Jun 15, 2015, 07:41 PM
#170
The breakaway torque on my re-stacked rear differential came down a bit after break-in, but it was still higher than I was comfortable with. My car was still chirping and clunking excessively during any low-speed turns.
I bought a cheap replacement LSD locally, re-stacked it, and put it on the car. Same method, but this diff is substantially quieter and more well-behaved. I just hope it behaves the same under autocross conditions, because my next even is the Utah match tour and I won't have a chance to practice before then.
I think I'll send the old diff in to TRE or Shep and have them do a proper stock rebuild on it. They must have plenty of stock LSD plates lying around after doing so many 12-plate builds, so hopefully they can get the 8-plate diff set up just right for me.
I bought a cheap replacement LSD locally, re-stacked it, and put it on the car. Same method, but this diff is substantially quieter and more well-behaved. I just hope it behaves the same under autocross conditions, because my next even is the Utah match tour and I won't have a chance to practice before then.
I think I'll send the old diff in to TRE or Shep and have them do a proper stock rebuild on it. They must have plenty of stock LSD plates lying around after doing so many 12-plate builds, so hopefully they can get the 8-plate diff set up just right for me.
Jun 16, 2015, 07:01 AM
#171
Shep and TRE must have plenty of stock plates going through their shops, so hopefully they'd be able to come up with a cheap solution if any of the plates do need to be replaced.
My new restacked diff behaves a whole lot better than my old restacked diff. It still locks up just right as soon as I really get on the throttle, but there's no low-speed chirping and steady-state bind like the first one I restacked. I'm tempted to pull the original one apart one last time before I send it to a professional and measure all of the plates and tolerances to see if I can figure out why it has so much more steady-state bind than this new one. I'm guess the stack height is just taller for some reason, as I've already confirmed that the spring plates are installed correctly in the last tear-down.
Jun 17, 2015, 04:05 AM
#172
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Has anyone gone and restacked/replaced the plates so that the diff is at the upper spec limit? I'm curious to know if the lockup at maximum is significantly better than the lockup in the middle or low end of the spec.
It sounds like a potentially spendy experiment for me to do, especially on a car that I don't seem to race anymore.
-Bryan
It sounds like a potentially spendy experiment for me to do, especially on a car that I don't seem to race anymore.
-Bryan
Jun 17, 2015, 07:57 PM
#173
Has anyone gone and restacked/replaced the plates so that the diff is at the upper spec limit? I'm curious to know if the lockup at maximum is significantly better than the lockup in the middle or low end of the spec.
It sounds like a potentially spendy experiment for me to do, especially on a car that I don't seem to race anymore.
It sounds like a potentially spendy experiment for me to do, especially on a car that I don't seem to race anymore.
I'm guessing my bad diff was actually out of spec (somehow) and I'm not sure you'd be able to get as much lockup as I had if you actually measured everything to spec. That said, I'm not convinced the extra lockup was an advantage, either. Having the diff always in semi-lockup meant that it was always dragging/binding a little bit. It was enough that I the driveline bind and parasitic drag was barely palpable while coasting through turns. I guess the only real advantage might be the lockup under decel, but I'm not sure if I noticed anything helpful there.
Perhaps I'm missing something or my old diff was somehow broken in some other way, but so far I'm happier with the in-spec, properly-behaving rear diff.
Jun 17, 2015, 08:38 PM
#174
Register for Wilmington! Quick!
http://www.motorsportreg.com/events/...al-tour-822559
Or at least, as quick as the software will let you.
We are up to 10 in STU already. 253 total registrants to a max of 325.
http://www.motorsportreg.com/events/...al-tour-822559
Or at least, as quick as the software will let you.
We are up to 10 in STU already. 253 total registrants to a max of 325.
Jun 18, 2015, 04:09 AM
#175
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I'm not an expert, but I did just rebuild and drive on two rebuilt diffs back-to-back that had different amounts of base lockup. The diff with too much breakaway torque, perhaps due to too thick of a stackup, didn't feel any better under hard acceleration.
I'm guessing my bad diff was actually out of spec (somehow) and I'm not sure you'd be able to get as much lockup as I had if you actually measured everything to spec. That said, I'm not convinced the extra lockup was an advantage, either. Having the diff always in semi-lockup meant that it was always dragging/binding a little bit. It was enough that I the driveline bind and parasitic drag was barely palpable while coasting through turns. I guess the only real advantage might be the lockup under decel, but I'm not sure if I noticed anything helpful there.
Perhaps I'm missing something or my old diff was somehow broken in some other way, but so far I'm happier with the in-spec, properly-behaving rear diff.
I'm guessing my bad diff was actually out of spec (somehow) and I'm not sure you'd be able to get as much lockup as I had if you actually measured everything to spec. That said, I'm not convinced the extra lockup was an advantage, either. Having the diff always in semi-lockup meant that it was always dragging/binding a little bit. It was enough that I the driveline bind and parasitic drag was barely palpable while coasting through turns. I guess the only real advantage might be the lockup under decel, but I'm not sure if I noticed anything helpful there.
Perhaps I'm missing something or my old diff was somehow broken in some other way, but so far I'm happier with the in-spec, properly-behaving rear diff.
I was asking about a diff that's in spec, just at the high end of the stack up height.
My interest is primarily in creating on throttle oversteer in corners. That's easily the biggest difference in the handling between the ASP Evo and the STU Evo.
If I can actually get that behavior in STU, it'll be well worth a few hundred dollars in plates, and it'll calm down the unrealistic desire to send my car down the classing road.
-Bryan
Jun 18, 2015, 12:39 PM
#177
Evolving Member
We're thinking about swapping out our rear diff fluid this weekend. Dallas, you used the Redline 75W140 "NS" ?? How much noise, honestly? We're looking for a little more lockup from our TRE restacked/rebuilt OE diff... but, not looking to mess it up, or shorten it's life either.
Other suggestions? We've been using Diaqueen.
Doug
Jun 18, 2015, 04:22 PM
#178
I was asking about a diff that's in spec, just at the high end of the stack up height.
My interest is primarily in creating on throttle oversteer in corners. That's easily the biggest difference in the handling between the ASP Evo and the STU Evo.
If I can actually get that behavior in STU, it'll be well worth a few hundred dollars in plates, and it'll calm down the unrealistic desire to send my car down the classing road.
My interest is primarily in creating on throttle oversteer in corners. That's easily the biggest difference in the handling between the ASP Evo and the STU Evo.
If I can actually get that behavior in STU, it'll be well worth a few hundred dollars in plates, and it'll calm down the unrealistic desire to send my car down the classing road.
If you want more lockup, I'd give the Redline NS fluid a try. It lacks the friction modifiers of traditional LSD fluid and thus should result in more lock-up. More friction means more wear, but that's to be expected.
I may try the Redline NS fluid after the Utah match tour.
Jun 19, 2015, 05:41 AM
#179
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I'm not sure if changing the stackup height within the spec range would make any difference in lock-up. As far as I can tell, the amount of pressure applied to the plates is a function of the ramp angle and the torque input to the differential. The only difference the stackup thickness would make is in how far the shells would have to separate before applying that pressure to the plates.
If you want more lockup, I'd give the Redline NS fluid a try. It lacks the friction modifiers of traditional LSD fluid and thus should result in more lock-up. More friction means more wear, but that's to be expected.
I may try the Redline NS fluid after the Utah match tour.
If you want more lockup, I'd give the Redline NS fluid a try. It lacks the friction modifiers of traditional LSD fluid and thus should result in more lock-up. More friction means more wear, but that's to be expected.
I may try the Redline NS fluid after the Utah match tour.
Hmmm. Thanks for the info.
Jun 19, 2015, 06:51 AM
#180
I'm not sure if changing the stackup height within the spec range would make any difference in lock-up. As far as I can tell, the amount of pressure applied to the plates is a function of the ramp angle and the torque input to the differential. The only difference the stackup thickness would make is in how far the shells would have to separate before applying that pressure to the plates.
If you want more lockup, I'd give the Redline NS fluid a try. It lacks the friction modifiers of traditional LSD fluid and thus should result in more lock-up. More friction means more wear, but that's to be expected.
I may try the Redline NS fluid after the Utah match tour.
If you want more lockup, I'd give the Redline NS fluid a try. It lacks the friction modifiers of traditional LSD fluid and thus should result in more lock-up. More friction means more wear, but that's to be expected.
I may try the Redline NS fluid after the Utah match tour.