1/4mi results in, how do they fair though?

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Jun 20, 2005 | 05:13 PM

#21

endo

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From: Socal

Let me disclaim the following by first saying that I'm the farthest thing from an expert here, so take it with a grain of salt...

While I've never personally seen such a thing happen, it almost sounds to me like its going from second to fourth. Is there any other way to see that kind of RPM drop? If the torque converter were locking up it wouldn't account for all that right?

What's the RPM cruising at 75mph....and what happens to the RPM when you then floor it from that 75mph cruise? (I'm assuming it will only kickdown to 3rd in such a case, but if 3.42s hit 2nd in such a case from 75mph, then replace the 75 figure with 80 or somesuch where it can only use 3rd).

Quote:

Originally Posted by s3gulit

I know i wasn't letting off before the end of the track, im 98% sure it has to be the 2-3 shift.

1st gear shifts at 5700 or there about, and shifts into second. Second gear starts at about 3400-3500rpm, and shifts at 5500 or thats what it looked like at a quick glance, then it shifts into third. Third gear starts off at 2000-2300 rpms, which then takes forever to get up in the MPH which is why everyone is saying that my trap speed is way below what it should be, and i believe if i have nelson change the 2-3 shift to have 3rd start off in 3200 then i should have raised trap speeds and a lower e/t. correct?

Please help me, its starting to **** me off that im .5-.8 slower than what most 4.8L's are running.

Dave

Jun 20, 2005 | 05:15 PM

#22

s3gulit

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Launching!

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From: IL

Quote:

Originally Posted by jleews6

I think we both have the same problem and that is the low rpm shift to third gear.

Yeah im pretty sure we do, lol, i emailed nelson performance about the pcm reprogramming and the 3rd gear rpm being so low, i'll tell ya what he says when i get an email back from him.

Dave

Jun 20, 2005 | 05:17 PM

#23

s3gulit

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Launching!

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From: IL

it's hard to shift into 4th when you have your shifter on 3 so the OD doesn't kick-in. Which is why im trying to resolve this problem...somehow. Sure a new converter is on its way in the next 3 weeks, but i doubt its going to solve my low-rpm problems in 3rd gear.

Dave

Jun 20, 2005 | 05:48 PM

#24

endo

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From: Socal

I just don't see how you can get a 4L60E to drop from 5500RPM to 2300RPM from 2-3. Just based on the math of the ratios, i.e., 1.75 vs. 1.00 it should be 3142RPM. Factoring in the torque converter lessens the accuracy of that math, but not to the extent of ~850 RPM. Again, my no means an expert, grain of salt, etc.

Quote:

Originally Posted by s3gulit

Jun 20, 2005 | 09:51 PM

#25

420

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i have an 02 rcsb with a 4.8 and the 3.42's. your 60' time is about right, the best i could get was a 2.405. your 1/8 mile time doesnt seem right at all, i was getting 10.4's all night in the 1/8, and i was even holding the gears manualy. what speed did you trap in the 1/8? i was getting 16.0's all night, but i was trapping in the high 88 mph range. the only thing i have done is a single in/dual out muffler. i think i could hit 15.8's or so on a different day, the humidity was at 85% and it was about 80 degrees out.

Jun 20, 2005 | 10:33 PM

#26

white1

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From: Sittin on jackstands

Try manually shifting. My 5.3 runs 15.5's and only uses 1st and 2nd with 3.73's When are you hitting 3rd? Try to shift 300 rpm past your peak power. Or and a old timer told me this. Shift 300 rpm's less than you go thru the traps. I only use 1st and 2nd, so its not possible for me to try.