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| 88BlackZ51 | Gears and Transmission for the 421 and Top Speed. | ||
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Gears and Transmission for the 421 and Top Speed.
Right now the car sits stored in the garage with the 4+3, and 3.07s gears. My motor is not far away from being completed so I need to think what gears its going to like with the black tag ZF6 I purchased. I have been talking to Vic89, and I am pretty sure I am going to purchase his old 3.45s. I am not sure if its the optimized gear for the car, but I am sure it will be better then the 3.07s. I also have a friend that has a set of 3.33s that I am going to get. I might leave the 4+3 in the car and see if it will handle the torque, or I might just do both of them at once. The latter seems like the smartest thing, then maybe I cam recoup some money selling the 4+3 since it has no issues what so ever. With the ZF6 here is the MPH from http://www.f-body.org/gears/ I am hoping this site is accurate, and I think it is. I plan on shifting at 6300, but that is on paper. 3.07s 1stGear-58 MPH 2ndGear-86MPH 3rdGear-120 MPH 4thGear-155 MPH 5thGear-207 MPH 6thGear-1200 RPM at 60 MPH (wow!) 3.33s 1stGear-53 MPH 2ndGear-80 MPH 3rdGear-111 MPH 4thGear-143 MPH 5thGear-191 MPH 6thGear-1300 RPM at 60 MPH 3.45s 1stGear-52 MPH 2ndGear-77 MPH 3rdGear-107MPH 4thGear-138MPH 5thGear-184MPH 6thGear- 1400 RPM at 60 MPH 3.73s 1stGear-48 MPH 2ndGear-71 MPH 3rdGear-99 MPH 4thGear-128 MPH 5thGear-170 MPH 6thGear- 1500 RPM at 60 MPH It appears that my top speed with 3.45s will be 184 MPH. Do you think I will have an issue getting to that speed? It looks like for pure top speed the 3.07s gear would be the one to go with, but since I cant drive on the airport strip every day, the 3.07s doesnt make sense, but 0-60mph (6400 shift) would be neat in one gear. If I went with 3.07 gears, do you think the car would be capable of reaching speeds close to 200 mph? Or do you think it would need more power? For all out ¼ mile it appears that the car would run the strongest with 3.73s as it would be capable of trapping 128 mph on the big end in 4th, but if I am going to put a 100-150 shot on the car, the 3.73s would be too much, and the 3.45s would be more in the cards since 138 mph would be top of 4th. I am thinking the 3.73s might be too much for the street. With the miniram it will have a very flat TQ curve, and make in the area of 400-420rwtq at 2000 rpms so I dont need a gear to get the car rolling especially with the smaller cylinder head ports. Its a very interesting decision. I will probably go with the 3.45s as they seem like the best overall gear. But then again, I wont know foresure until I drive the car. I also don't think there is a perfect gear with the ZF6. Have a good one guys! |
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Posted on: 2008/11/13 17:39
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| bogus | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Grand Imperial Pooh-Bah
 
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You might come close... but I kinda doubt it... aero drag is a bitch.
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Posted on: 2008/11/14 1:34
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| pr0zac | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Elite Guru
 
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my car would hit 138 like it was its job stock in 4th. and have done 150 stock fairly easily. since geting a ticket for 95 in a 45 and since i haven't bothered going that fast. i now have 4.10's so i don't know how that is going to be with the new motor. haven't driven it except on and off the trailer at the exhaust shop.
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Posted on: 2008/11/14 1:49
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| cuisinartvette | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Gear it where the cam is going to like it the most, dont do it for top or cruising speed.
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Posted on: 2008/11/14 1:53
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Come close to what 200 mph? Wonder how much power it takes for a C4 to reach 190'ish? Not really worried about 200. I know it won't have that kind of power! |
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Posted on: 2008/11/14 1:56
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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That is probably 3.73's. 4.10's would be way to much for the stroker. The issue is the 3.73's will be great at the track with a hook. I bet it would get deep in the 11's, but I have never been worried about e.t. It will be fun anyways. Nothing like a manual tranny with over 500hp, and shifting like you stole it. |
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Posted on: 2008/11/14 1:57
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| CentralCoaster | Re: Gears and Transmission for the 421 and Top Speed. | ||
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With the right gearing, 200 doesn't take as much as you think. I posted the breakdown somewhere else, I'll see if I can't find it. http://www.corvette-guru.com/modules/ ... =ASC&type=&mode=0&start=0 My posts in that thread have 200mph happening at about 450rwhp in a C4 with proper gearing and enough track. |
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Posted on: 2008/11/14 2:05
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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You have about 600hp as well, lol!! Kevin did you get my email. I'd would think Jim will get back to us with the dyno graph. |
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Posted on: 2008/11/14 2:11
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| jsup | Re: Gears and Transmission for the 421 and Top Speed. | ||
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If this is a street car, why not street gears...just wonderin...
The goals seem to be all over the place...1/4 mile, top end, street... Pick one and go with it. There is no one all around solution. |
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Posted on: 2008/11/14 2:29
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Probably just go with the 3.45's. That way I have room to grow if I ever decide to spray it. The bottom end will certainly handle it! 3.73's would be fun however! |
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Posted on: 2008/11/14 2:36
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| jsup | Re: Gears and Transmission for the 421 and Top Speed. | ||
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That sounds as close as you're going to get to an "all around" gear, from what I understand, which, ain't much.
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Posted on: 2008/11/14 2:43
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Not following you. What "ain't much"? |
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Posted on: 2008/11/14 2:52
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| jsup | Re: Gears and Transmission for the 421 and Top Speed. | ||
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What I understand, ain't much.
I hear the 6 speed guys saying 3.45 works for them, anecdotal, but seems to work. Is there not an expert you can find locally on the issue? Someone who's core business is trans and rear service? |
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Posted on: 2008/11/14 2:57
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| cuisinartvette | Re: Gears and Transmission for the 421 and Top Speed. | ||
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What does your builder recommend?
Personally Id go for 3.73s on drag radials at all times. 3.45 may get you by though. Forget about all that top speed crap, its going to pull 5th well anyway due to sheer CI size. |
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Posted on: 2008/11/14 3:10
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| jsup | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Why would he ask an engine builder? Do you mean in terms of getting the engines operational range of the cam to match the gears? Wouldn't it make more sense to go to a trans/rear guy? He said all along it was a "street car" which I would assume would not be on drag radials. If the goal is streetable, 3.45, no? I think he said "occasional" track use. |
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Posted on: 2008/11/14 3:19
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| cuisinartvette | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Im sure 3.45s would work well....Recommended he consult his builder as he apparently does a lot of these 420/421 cube motors and probably knows where it will like to run better than most would is my guess.
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Posted on: 2008/11/14 3:29
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| CentralCoaster | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Top speed is never a consideration, just a "what if"
A good 1/4 mile gear (assuming you finish in 4th) will also be a good street and highway gear. But I need a dyno curve before I can be your gearing "expert". |
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Posted on: 2008/11/14 3:44
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Posted on: 2008/11/14 4:05
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| bogus | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Grand Imperial Pooh-Bah
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pulling 5th isn't the problem... it's pulling 6th. 5th is ~.75:1 OD, that is where top speed is seen; 6th is ~.50:1, the amount of torque needed to overcome that gear is staggering. |
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Posted on: 2008/11/14 15:22
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| cuisinartvette | Re: Gears and Transmission for the 421 and Top Speed. | ||
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True..from what I understand they dont recommend topping these out in 6th as some damage reults, something about the reverse gear seizing up. Sure ZF doc can explain it better.
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Posted on: 2008/11/14 15:49
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| LT4BUD | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Can you post it??? |
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Posted on: 2008/11/14 16:55
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Don't know how 2. I sent it to CentralCoaster.
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Posted on: 2008/11/15 0:47
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| CentralCoaster | Re: Gears and Transmission for the 421 and Top Speed. | ||
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My simulation with a ZF6, 26" tires, 3400 lb race weight, 1.70 60ft:
Shift point: 6350 RPM 3.45 rear: 10.56 @ 128.4, top speed 191mph in 5th 3.55 gear: 10.56 @ 128.5, top speed 188mph in 5th 3.73 gear: 10.61 @ 128.3, top speed 193mph in 6th 3.90 gear: 10.65 @ 127.2, top speed 196mph in 6th 4.11 gear: 10.70 @ 127.0, top speed 199mph in 6th Anything above that requires shifting into 5th. |
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Posted on: 2008/11/15 3:49
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Kev thanks!
Is it possible for the car to pull in 6th? What 60 foot did you use? Thanks again. That was cool! |
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Posted on: 2008/11/15 4:01
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| jsup | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Stupid question, on a 6350 shift, aren't you testing the limits of a hydraulic roller? I believe 6500 is about the hairy end of an HR setup. Riding it to 6700 isn't about the capacity of HR? Or am I just over cautious? For the time differences, and since this was built as a street car, I'd go 3.45, the gains aren't enough on the other gears to tool around at high RPMs. |
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Posted on: 2008/11/15 4:03
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| CentralCoaster | Re: Gears and Transmission for the 421 and Top Speed. | ||
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My sim isn't good at figuring 60' times, because in reality dumping the clutch puts a lot more energy to the rear wheels, more than than the peak torque of the engine, and I haven't figured out how to model that yet.
I went back and edited them all to a 1.7 60' and see which wins out. Makes more sense this way, as the 4.11s were way past the power curve. How does gearing effect the 60'? Is a shorter gear always better? |
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Posted on: 2008/11/15 7:15
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| Josh | Re: Gears and Transmission for the 421 and Top Speed. | ||
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I think deeper gears will be more fun, so I would go 3.9XX or 4.09. For me, fun = number 1. Everything else is secondary to how fun the car is to drive.
If you drag race, I think the deeper gear will be faster, regardless of what the sim says. The steeper gears make wheel spin infinitely more manageable, and makes the car much easier to launch effectively. If you put a sticky tire under it that can handle a 4-5K clutch drop, the 3.45's might be faster, but even then I have my doubts. |
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Posted on: 2008/11/15 14:54
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| jsup | Re: Gears and Transmission for the 421 and Top Speed. | ||
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He's maintained this is a street car first, pulling 3K on the highway isn't attractive to me, but it's his car. Also, this thread asks about top speed. So it's hard to tell where his head is at. Do we believe his original claim of street car, his thread on top speed, or his current position of 1/4 mile. It's all so confusing to me. |
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Posted on: 2008/11/15 14:59
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| AKS_Racing | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Although I agree that with a 6 speed the deeper gears are more fun around town, I ran into issues with running out of gear in the 1/4 mile. I have a set of 3.54s, a 3.7 and a 4.10 all spare chunks, and I could make none of them work. With the tires I run at the track, if I get much faster, I will have to go to a 3.33D44 (which I really don't want to do). Aaron |
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Posted on: 2008/11/15 15:10
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| Josh | Re: Gears and Transmission for the 421 and Top Speed. | ||
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3,000 RPM's and a 4.09 gear works out to 116 MPH in 6th gear with a ZF6. No one cruises the freeway at 116 MPH. At a more reasonable 75 MPH he would be turning an entirely livable 1950 RPM's. If he goes 3.92, 75 MPH would be 1875 RPM's, which is also entirely livable. Where do you come up with 3K? He could run a 4.88 gear and still only be turning 2350 RPM's at 75 MPH. To see 3,000 RPM at 75 MPH he would have to run a 6.13 rear gear. |
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Posted on: 2008/11/15 16:41
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| jsup | Re: Gears and Transmission for the 421 and Top Speed. | ||
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ooops, You're right, my frame of reference is my 700R which runs about 2200 RPMS with the 3.07..at about 70ish I find more than that annoying...Sorry, frame of reference issue, gotta get my head out of the auto. |
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Posted on: 2008/11/15 16:45
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| Josh | Re: Gears and Transmission for the 421 and Top Speed. | ||
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No worries man. :cheers:
As far as him running out of gear in the 1/4 mile, as long as he is willing to turn 6500 he should be able to go 130 or so in 4th with the 3.9XX or 4.XX gear. |
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Posted on: 2008/11/15 16:57
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| bogus | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Grand Imperial Pooh-Bah
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I still question the ability of the 6th gear to do much... even with more rear gear...
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Posted on: 2008/11/15 18:18
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| Josh | Re: Gears and Transmission for the 421 and Top Speed. | ||
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I don't think it'll pull it in 6th regardless of rear gear.
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Posted on: 2008/11/15 18:35
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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I don't think so either, but then again it's going to have a very flat tq curve. Topspeed isn't really important, but I do have an airport near by that has a very long runway. I was on it 2 years ago, but the car was mainly stock. It would be cool however for it to do in the 19x mph mark, and run the 1/4 somewhere in the 11's. Somewhat sleeper territory if you ask me. |
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Posted on: 2008/11/15 19:24
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| bogus | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Remember... the new ZR1 has 640hp/575ft-lbs and still gets to 205 in 5th.
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Posted on: 2008/11/16 2:00
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| CentralCoaster | Re: Gears and Transmission for the 421 and Top Speed. | ||
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That's ridiculous. The engine doesn't care how many teeth are in the trans, all it sees is the overall ratio. The numbers I posted pretty much show that 6th overtakes 5th if the rear is short enough. Obviously it'll take forever to get that last few mph though. |
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Posted on: 2008/11/16 3:41
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| Josh | Re: Gears and Transmission for the 421 and Top Speed. | ||
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All I meant was that 6th gear has a torque reduction/speed increase as opposed to speed decrease/torque increase like the lower gears. I realize 5th does the same thing, but I've never seen 6th gear actually used for top speed. You've shown that it is doable though, so I apologize for the ambiguous statement that I made.
In our particular application, 6th gear can't be used as the top speed gear due to design issues with the ZF6 transmission, so it's really a moot point for this discussion. |
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Posted on: 2008/11/16 16:27
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| 88BlackZ51 | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Did you have any issues with the 3.07's/ZF6 combo? |
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Posted on: 2008/11/18 10:35
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| CentralCoaster | Re: Gears and Transmission for the 421 and Top Speed. | ||
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Way too tall. You couldn't use 6th until about 85mph. So I ended up driving 90 everywhere whether I wanted to or not!
Its first gear is a little taller than the 4+3 also, better suited to a 3.33/3.45/3.55. I went with the 3.45 as it made the most sense in the 1/4 mile and does 75 mph at 1800 rpms. In the 1/8th I would've been better off taller. |
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Posted on: 2008/11/18 15:12
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