rpm drop at gear change??
#2370953
09/14/17 10:09 PM
09/14/17 10:09 PM
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Joined: Jan 2004
Posts: 13,247 Mt. Vernon, Ohio
dartman366
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OP
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what is a normal/acceptable rpm drop at gear change? my dart has a 8" 5200 stall ultimate behind the 512 and 1st to second shift drops 570 rpm and so does second to third,,does this sound about right? more info upon request.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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Re: rpm drop at gear change??
[Re: dartman366]
#2371068
09/15/17 01:25 AM
09/15/17 01:25 AM
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Joined: Aug 2003
Posts: 43,317 Bend,OR USA
Cab_Burge
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What is your shift RPM? I would try upping the shift rpm by 500 RPM and see if the RPM drop is the same as before If so that is all you are going to get with that tranny and converter If it widens out the RPM drop then you need to think about what you want to do, shift it higher or take the converter out and have it work on so it drops the normal % RPM which should be around 1200 to 1300 RPM on a stock 1st and 2nd gear set in a 727 at or above 6000 RPM
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: rpm drop at gear change??
[Re: dartman366]
#2371122
09/15/17 09:47 AM
09/15/17 09:47 AM
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Joined: Nov 2011
Posts: 289 PA
Harry's Taxi 2
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We don't seem to have a clear opinion on this question. A range of 570-1500? I'm trying to find the answer to this question myself right now.....3 converter changes and a rear gear change(don't know the result of the gear change yet)so far. I have learned that a 300 rpm drop is not the answer......and a 600 rpm drop isn't quite the ticket yet either. In looking at some in-car camera shots of a SS/AH car on an 8.60ish run, it looks like around 1000 rpm drop or more seems closer.
Just to clarify this, I assume we're talking 3-speed's in everyone's reply?
'86 Maple Grove KOS Mopar low qualifier......true street legal with no power adders.
NOS-used when losing since 1940.
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Re: rpm drop at gear change??
[Re: dartman366]
#2371183
09/15/17 12:45 PM
09/15/17 12:45 PM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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There is no single correct answer for this. Every combo will have it's own requirement.
My opinion on the OP's combo......511, small heads and intake(std port window), not a huge cam...... Is that 570rpm drop is not enough. I would think a 6500-ish rpm shift point, along with about a 1000rpm drop after shifting would work a bit better(assuming the reworked converter doesn't give up any multiplication or efficiency).
Member Wookie was fighting some converter issues last year with his Charger.
He had a couple of good you tube videos of the tac with the two different converters. The first one you could see the motor was just driving right through it. The second one really allowed the motor to work with the big mid-range tq numbers and had way more drop between gears...... Along with much better top end efficiency....... And the car was quite a bit quicker and faster as a result.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: rpm drop at gear change??
[Re: dartman366]
#2371228
09/15/17 02:47 PM
09/15/17 02:47 PM
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Joined: Dec 2005
Posts: 11,747 Fulton County, PA
CMcAllister
Mr. Helpful
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RPM drop on the gear change is a simple math problem using gear ratios and engine RPM to figure what driveshaft RPM should be IF the clutch or converter were direct drive with zero slippage. Slippage in the bellhousing makes the answer anything but cut and dried.
Shift points vs. converter stall/slippage is used as a tuning tool for some folks. Some want the RPM to fall back below the stall speed to get the converter back into torque multiplication a bit. Others want to stay above that point with engine speed. Depends on the combo and what you are trying to accomplish. Usually, with the correct converter for the application, a shift point 1000 to 1200 above stall speed - maybe a bit less with a 3 speed - is a good place to start.
If the results don't match the theory, change the theory.
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Re: rpm drop at gear change??
[Re: dartman366]
#2371233
09/15/17 03:09 PM
09/15/17 03:09 PM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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Slippage in the bellhousing makes the answer anything but cut and dried. Not only that, but you can take two converters from different suppliers that exhibit nearly identical characteristics(flash stall, drop between gears, slippage in high gear), and find they produce different ET's. Of my own combos, the one I did the most experimentation with shift points on was the 383. The best ET's with that came from shifting 1-2 @6000, 2-3 @6500, trap rpm 6900-7000 depending on weather. This was with a 5400 flash stall converter. The 1-2 shift came really quick, and would just put the motor back on the converter(400rpm drop). This was about .02 or so quicker than shifting the 1-2 @6500. Shifting @7000 really felt awesome...... Like you were setting the world on fire..... But it never resulted in a good number on the time slip. Shifting 1-2 @6000 felt like you just killed it..... But it always put up a good number.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: rpm drop at gear change??
[Re: dartman366]
#2371243
09/15/17 03:28 PM
09/15/17 03:28 PM
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Joined: Dec 2005
Posts: 11,747 Fulton County, PA
CMcAllister
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Getting back into torque multiplication on the 1-2 change can help the engine recover. That's the theory, as told to me. Longer strokes, bigger cubes, flatter torque curves - it's not as helpful.
If the results don't match the theory, change the theory.
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Re: rpm drop at gear change??
[Re: dartman366]
#2371278
09/15/17 04:05 PM
09/15/17 04:05 PM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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Same converter, same car, but with 5.13's instead of 4.56's...... And a higher strung 340 instead of the 383. 500rpm less flash stall, and if you shifted any lower than about 7200 the ET's fell right off.
I don't recall what the rpm drop was with that motor in the car, but the combination of less tq, higher rpm shifts(more converter lock up), and lower gear resulted in a much larger drop after the shift. The best ET's with that combo came from shifting at about 7500.
That motor had about 65ft/lbs less tq, and it peaked about 500rpm higher than the 383.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: rpm drop at gear change??
[Re: DoubleD]
#2371334
09/15/17 05:49 PM
09/15/17 05:49 PM
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Joined: Nov 2011
Posts: 289 PA
Harry's Taxi 2
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The more the drop the looser the converter will be - i.e stall speed - if you shift below or near your stall speed you are going to see a bigger drop - every converter is different and no two are identical - its what works for your combo - only true way to know what converter is best for your car is to have a dyno sheet from the engine and have the converter built to the specs of your car weight, rear gear etc. - even then its still a bit of an art and S.W.A.G - I have watched Marco Abbruzi test ten different converters in his car in a single day - just to find the right one I think you have that a little backwards....tighter converter will drop the rpm's more on the shift. With some of the converter suggestions/results I've seen from some well advertised converter companies, I'm not sure I'd trust the newer kids on the block.
'86 Maple Grove KOS Mopar low qualifier......true street legal with no power adders.
NOS-used when losing since 1940.
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Re: rpm drop at gear change??
[Re: Harry's Taxi 2]
#2371448
09/15/17 10:05 PM
09/15/17 10:05 PM
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Joined: Jan 2004
Posts: 13,247 Mt. Vernon, Ohio
dartman366
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to add a little more info, the car has 4.56 gearing and 14X32X15 phoenix slicks, weight is around 3150# race weight, I launch off the T-brake at 3500 and shift at 6500, this is up from 6200 and resulted in a quicker ET and allowed the car to pull further down track, this info is is from using my LM-2 checking my AFR's,,,,which is another story.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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Re: rpm drop at gear change??
[Re: dartman366]
#2372591
09/18/17 10:29 AM
09/18/17 10:29 AM
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Joined: Mar 2003
Posts: 2,527 PA
moparacer
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Never liked a tight converter in anything. And just about everything I loosened up went quicker. But I shoe polish race. Car I been running drops 400 rpm at the shift.
67 Barracuda street/bracket car 11.27-119 68 Dart 502 BB 8.70s-152 414 cid SB Dragster 7.65-174
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Re: rpm drop at gear change??
[Re: moparacer]
#2372760
09/18/17 03:20 PM
09/18/17 03:20 PM
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Joined: Aug 2003
Posts: 43,317 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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Never liked a tight converter in anything. And just about everything I loosened up went quicker. But I shoe polish race. Car I been running drops 400 rpm at the shift. I wouldn't have let that rascal live in my car more than one race, way to loose for me Or is this a glide? I've had the opposite experiences with a Art Carr 8 inch loose converter that drop less than 1000 RPM on the gar change shifting at 7000 RPM, it would flash to 7000 in 1st gear and drop back to 6000 RPM or so and then drop back to 6000 RPM on both gear changes, NOT GOOD We ended up with a BM O69J nine inch in that car and it picked up .6 et and 5 mph I've also had the same experience you have had with a looser converter in my old pump gas Duster, took out a tight 10 inch converter and put in a T/A SS Hemi 8 inch converter and picked that car up .23 in the 1/8 mile and 2 mph If you don't test, you don't learn
Last edited by Cab_Burge; 09/18/17 03:26 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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