Re-gearing 5th gear?, Can it be done? |
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Re-gearing 5th gear?, Can it be done? |
ahdoman |
Jan 21 2007, 11:06 PM
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#1
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It's phonetic...Ah-D-O-Man (Audioman) Group: Members Posts: 667 Joined: 7-November 05 From: Santa Clarita, Ca. Member No.: 5,084 Region Association: Southern California |
Is there a way to re-gear 5th so that it acts more like an overdrive? On the freeway at 75 the RPM's are around 3500 and with the Bursch exhaust it is quite loud in the car. Anybody ever done this?
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Aaron Cox |
Jan 21 2007, 11:09 PM
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#2
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
witha 4 banger.... you dont want to go any taller.....
any fewer RPM's and it will overheat..... rpm's turn the fan... which in turn cool the motor... 3200 rpm seems to be the magic number..... wont cool well below that under load... |
Twystd1 |
Jan 21 2007, 11:15 PM
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#3
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You don't want to know... really..... Group: Members Posts: 2,514 Joined: 12-September 04 From: Newport Beach, California Member No.: 2,743 |
Put a quieter muffler on the car...
Your gearing is correct right out of the box. C |
Aaron Cox |
Jan 21 2007, 11:19 PM
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#4
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
fifth is already pretty dang tall....
as tall as i would go with a 4... or even a 6. factory 6's were geared SHORTER to keep em cool... and get em into the RPM they were designed to cruise at.... Attached image(s) |
nebreitling |
Jan 21 2007, 11:26 PM
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#5
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Member Emeritus Group: Members Posts: 3,314 Joined: 26-March 03 From: San Francisco Member No.: 478 |
aaron and co. are correct, but to answer your question, yes -- there are taller gears available. the v8 guys use them for cruising. ill-advised for your /4, even if you drive really really fast.
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Aaron Cox |
Jan 21 2007, 11:30 PM
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#6
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
technically NO. there are no taller ratios...
you have to FLIP or reverse the ratio of 4 speed second gears.. such as flipping an H, HA or HB.... |
PRS914-6 |
Jan 22 2007, 12:01 AM
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#7
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Excellence Magazine Project 914 3.6 Group: Retired Members Posts: 1,278 Joined: 20-May 06 From: Central California Member No.: 6,031 Region Association: None |
Yep, I took an "I" gear and flipped in for 5th
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Mueller |
Jan 22 2007, 12:16 AM
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#8
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914 Freak! Group: Members Posts: 17,146 Joined: 4-January 03 From: Antioch, CA Member No.: 87 Region Association: None |
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ClayPerrine |
Jan 22 2007, 08:03 AM
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#9
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Life's been good to me so far..... Group: Admin Posts: 15,469 Joined: 11-September 03 From: Hurst, TX. Member No.: 1,143 Region Association: NineFourteenerVille |
If you are on stock 165SR15 tires, then no, you don't want to change the 5th gear. If you are on shorter tires, like 195/50-15 or 205/50/15 tires, then you might want to think about changing 5th. The RPM you turn on the freeway is directly related to both tire size and engine gearing. If you mess with the tire size, you can get back to a lower RPM by changing 5th.
It is an involved process to change 5th, as you have to disassemble the whole gear stack. But if you do it right, it is worth it. |
Eric_Shea |
Jan 22 2007, 10:42 AM
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#10
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PMB Performance Group: Admin Posts: 19,275 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains |
QUOTE witha 4 banger.... you dont want to go any taller..... any fewer RPM's and it will overheat..... rpm's turn the fan... which in turn cool the motor... 3200 rpm seems to be the magic number..... wont cool well below that under load... Solution... drive faster (IMG:style_emoticons/default/w00t.gif) |
Aaron Cox |
Jan 22 2007, 10:44 AM
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#11
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
i do (IMG:style_emoticons/default/smile.gif)
thats my chart up there.... i have a shortgeared box with a big gap to ZD fifth for cruising.... |
smontanaro |
Jan 23 2007, 07:52 PM
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#12
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Senior Member Group: Members Posts: 1,190 Joined: 3-June 05 From: Evanston, IL Member No.: 4,197 Region Association: Upper MidWest |
Can the drive ratio of the fan be increased so the fan spins at the same speed at lower RPMs (/6 or /4)?
Skip |
Aaron Cox |
Jan 23 2007, 08:52 PM
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#13
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
on a /4 its crank driven... use shorter gears or shorter tires to spin it faster....
im sure you can get overdrive pulleys for a six |
Eric_Shea |
Jan 23 2007, 09:10 PM
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#14
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PMB Performance Group: Admin Posts: 19,275 Joined: 3-September 03 From: Salt Lake City, UT Member No.: 1,110 Region Association: Rocky Mountains |
I'm in the thought process here for my GT clone.
Tranny's are Urdu to me. I have Greg Dondero's close ratio short box. I was thinking I would probably never see 5th at a track with that so 5th could actually be set for best mileage (cooling as well, but I do have a front cooler) at 75-80mph. Would a -4 5th gear work? (IMG:style_emoticons/default/confused24.gif) From looking at that chart a ZA would be right at the edge of my powerband. |
brant |
Jan 23 2007, 09:51 PM
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#15
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914 Wizard Group: Members Posts: 11,624 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
eric,
if your going to bother opening that box.... then don't make 5th into a highway gear instead make it into a useable race gear. you likely won't be using 1st gear very often on the track anyways so don't cripple yourself and turn your car into a 3 speed. at a minimum make 5th useable so that you at least have a useable 4 speed. its really really nice... trust me. brant (using all 5 speeds on the track F/J/O/S/V) |
McMark |
Jan 23 2007, 10:01 PM
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#16
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
I'm with Mueller, 205/50s really raise the cruising RPM. How about a set of 'cruizer' wheels and tires? Probably quite a bit cheaper than tranny work.
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SGB |
Jan 23 2007, 10:28 PM
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#17
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just visiting Group: Members Posts: 4,086 Joined: 8-March 03 From: Huntsville, AL Member No.: 404 Region Association: South East States |
I was thinking about a flipped 908 2nd gear ("I" ratio, I think), but it was too much gonna be some large $ b/c a new mainshaft is also required. Instead, I think my next tires may be mismatched. Maybe 205/55 in back and 205/50 or 195/55 in front. Hmmmmm.
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Aaron Cox |
Jan 23 2007, 11:18 PM
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#18
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
correct - you cannot change 5 speed's 2nd gear due to the gear being part of the mainshaft.... (F, GA)... you need a splined 904 shaft... OR you can CUT the second gear off and try to have one welded on (talk to brant or foley)
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