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Benefits of a higher first gear ratio transmission #1167544 01/29/12 12:50 AM 01/29/12 12:50 AM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Looking for real world experience with using a trans that has a higer ratio than the stock 727's 2.45? For example the 904 has a slightly higher 2.74 and some of the GM stuff has a 3.06 or the new TCI 6x speed that has a 2.97. FYI - running 3.73 gears, 28" tire, 3800Lb car. Thanks -C

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167545 01/29/12 01:17 AM 01/29/12 01:17 AM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog Striving for excellence
Kern Dog Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	John Kunkle would know for sure, but I think that all 904 transmissions were the 2.45 ratio first gear. It was the 998 and 999 transmissions that utilized the lower first and second gear set. They looked identical on the outside and used the same trans pan though. I had a 999 in a Duster. The original 904 lost 1st and reverse, so I went with an '83 999 trans from a Diplomat police car. The deeper gear made the car feel as if I just switched from the 3.21 axle gear to a theoretical 3.50 ratio. Better off the line performance with the same final drive ratio of the standard 904. Not bad, except the lockup torque converter would sometimes shudder when slowing down in 3rd. That trans finally took a crap and I went back with a standard 904. Wow... the LOSS felt more dramatic than the gain I once had.

Re: Benefits of a higher first gear ratio transmission [Re: Kern Dog] #1167546 01/29/12 02:28 AM 01/29/12 02:28 AM
Joined: Aug 2007 Posts: 1,819 Middle of A Field O OrangeProwler top fuel
OrangeProwler top fuel O Joined: Aug 2007 Posts: 1,819 Middle of A Field	I was told about two tenths in the 1/4 mile. The later 904s I think starting in the very late 70s maybe 1980 started using the lower gears in the transmission. I had a 90 Dakota with the small 3.9 and A500 and that's low first gear got me off the line good especially with 3.55 gears.

Re: Benefits of a higher first gear ratio transmission [Re: OrangeProwler] #1167547 01/29/12 11:54 AM 01/29/12 11:54 AM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Quote: I was told about two tenths in the 1/4 mile. The later 904s I think starting in the very late 70s maybe 1980 started using the lower gears in the transmission. I had a 90 Dakota with the small 3.9 and A500 and that's low first gear got me off the line good especially with 3.55 gears. So if I had a 727 with a 2.45 first vs another trans option with a 3.09 the second one would definitely have a significant advantage and definitely feel the difference - right? -C

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167548 01/29/12 04:40 PM 01/29/12 04:40 PM
Joined: Feb 2003 Posts: 415 Indiana P Pentastar440 mopar
Pentastar440 mopar P Joined: Feb 2003 Posts: 415 Indiana	The advantage of having a lower (higher numerically) 1st gear , would be a heavy car with a high geared rear end. A lighter car with a low rear end like 4:10 might not like a low 1st gear and may have excessive tire spin. That low 1st gear is to help a heavy car to get moving. '65 Belvedere II - 446-Indy,727 transbrake,Dana 4.56 '38 Plymouth 4Dr - 408SixPack, A518, Dana60 4:10

Re: Benefits of a higher first gear ratio transmission [Re: Pentastar440] #1167549 01/29/12 10:01 PM 01/29/12 10:01 PM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Quote: The advantage of having a lower (higher numerically) 1st gear , would be a heavy car with a high geared rear end. A lighter car with a low rear end like 4:10 might not like a low 1st gear and may have excessive tire spin. That low 1st gear is to help a heavy car to get moving. So If I were to say have a 67 Belvedere wagon it would probably be a good thing - right

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167550 01/29/12 11:18 PM 01/29/12 11:18 PM
Joined: May 2004 Posts: 1,377 Back In Iowa B belv2vert66 pro stock
belv2vert66 pro stock B Joined: May 2004 Posts: 1,377 Back In Iowa	My 66 dart which is relatively light has a a low gear set in the 904 with 3.91 gears in the rear. The car leaves decently and hooks well with drag radials. I am running a 318 built to the 400 hp recipe. I like the low gear set and feel like it really helps, but to be honest I don't have anything to compare it to.

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167551 01/30/12 03:24 PM 01/30/12 03:24 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	I installed a 274 ist 1.55 second gear set in my 727 (the gear set changes first and second) gained a tenth in the quarter aint cheap. stock gears are 2.45 1st and 1.45 second! definately a boost for heavy cars. If you swap the 727 for a 277 geared 904 you can gain about 2 10ths.

Re: Benefits of a higher first gear ratio transmission [Re: Dodgem] #1167552 01/30/12 04:16 PM 01/30/12 04:16 PM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Quote: I installed a 274 ist 1.55 second gear set in my 727 (the gear set changes first and second) gained a tenth in the quarter aint cheap. stock gears are 2.45 1st and 1.45 second! definately a boost for heavy cars. If you swap the 727 for a 277 geared 904 you can gain about 2 10ths. Would it make a noticeable difference in a mostly street driven car? I see quite a few reply's about the gains in track time. I am actually considering a tranny that has a 3.06 first, 1.65 second, 1.0 third and a .7 O/D Thanks Chad

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167553 01/30/12 04:46 PM 01/30/12 04:46 PM
Joined: Sep 2004 Posts: 2,091 oberlin, Ohio Rapid340 top fuel
Rapid340 top fuel Joined: Sep 2004 Posts: 2,091 oberlin, Ohio	Chad, I think you will find the ratios in the OD too far apart for a performance car. Try finding an early trans with a 3.09 1st gear and a 1:1 4th. 1971 Factory Appearing Duster 340 11.000 @ 122 mph

Re: Benefits of a higher first gear ratio transmission [Re: Rapid340] #1167554 01/30/12 04:53 PM 01/30/12 04:53 PM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Quote: Chad, I think you will find the ratios in the OD too far apart for a performance car. Try finding an early trans with a 3.09 1st gear and a 1:1 4th. Heavy wagon and looking for cruising at a comfortable rpm on the highway, so need more O/D than 1:1 as at 70 I would be turning 3300. The car is close to 4000lb and had 3.73 rear gears with 28" tall tires.

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167555 01/30/12 07:18 PM 01/30/12 07:18 PM
Joined: Jul 2007 Posts: 1,682 Philadelphia R radar top fuel
radar top fuel R Joined: Jul 2007 Posts: 1,682 Philadelphia	I run an iron case 833OD behind a 408 LA in a '72 demon. 1st gear is fun but you do have to be careful if you want to plant a launch. 2nd gear screams up to highway speeds easily, 3rd is for lugging behind grandma on 35mph roads or playing with the power band on the highway. .71 OD is for cruising 75mph around 2500rpm. I do miss the close ratio box a little (ran one for a while) but it always seemed like I would rip up to 4th real fast and want another gear. I guess I could just launch in 2nd and shift to 3rd like a PG if I wanted to experiment with that? I definitely don't use the secondaries in OD but I trust the other gears to hold whatever I throw at them. It's a recently rebuilt trans from Jamie Passon. (not the fancy new 5 spd, the old a833OD) I guess it depends on how narrow your power band is and how you want to drive the car. I just put in an MP 557 cam and the car is way smoother lugging in traffic below the power band. With my torquier old cam it was less fun to have the gear spread but probably faster overall with the broader torque curve and long gears. Anyway, If you are going to do lots of highway cruising and still want to break the tires loose and skid around the 833OD will do it for ya.

Re: Benefits of a higher first gear ratio transmission [Re: Rapid340] #1167556 01/30/12 07:32 PM 01/30/12 07:32 PM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Quote: Chad, I think you will find the ratios in the OD too far apart for a performance car. it's way way off, too wide a spread between the 2 particular gears. it was not right even in a DD grocery getter. Alot of torque at your disposal would help cover the hole a bit but for a serious effort I'd suggest a diff route live every 24 hour block of time like it's your last day on earth

Re: Benefits of a higher first gear ratio transmission [Re: RapidRobert] #1167557 01/31/12 12:10 AM 01/31/12 12:10 AM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Quote: Quote: Chad, I think you will find the ratios in the OD too far apart for a performance car. it's way way off, too wide a spread between the 2 particular gears. it was not right even in a DD grocery getter. Alot of torque at your disposal would help cover the hole a bit but for a serious effort I'd suggest a diff route Are there any calculators out there that could show the max speed in each gear with particular ratios with different rear gears? -Chad

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167558 01/31/12 12:27 AM 01/31/12 12:27 AM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	Seems like a lot of work to get 1 mile to the gallon better fuel mileage on the highway??

Re: Benefits of a higher first gear ratio transmission [Re: Dodgem] #1167559 01/31/12 12:45 AM 01/31/12 12:45 AM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Quote: Seems like a lot of work to get 1 mile to the gallon better fuel mileage on the highway?? What calculation are you using? The o/d will drop rpm with 3.73 rear gear and 28" tire as follows stock 1:1 = 3133 RPM .78 = 2433 RPM .70 = 2193 RPM Is that accurate that 700-900 rpm drop would only be 1 MPG? -C

Re: Benefits of a higher first gear ratio transmission [Re: ramman5600] #1167560 01/31/12 01:06 AM 01/31/12 01:06 AM
Joined: Feb 2010 Posts: 18,493 Granite Bay CA Kern Dog Striving for excellence
Kern Dog Striving for excellence Joined: Feb 2010 Posts: 18,493 Granite Bay CA	Its late and Dodgem likes his beer. The gains would certainly be better than 1 mpg.

Re: Benefits of a higher first gear ratio transmission [Re: Kern Dog] #1167561 01/31/12 01:14 AM 01/31/12 01:14 AM
Joined: Jan 2008 Posts: 669 Michigan, USA R ramman5600 OP mopar
ramman5600 OP mopar R Joined: Jan 2008 Posts: 669 Michigan, USA	Quote: Its late and Dodgem likes his beer. The gains would certainly be better than 1 mpg. I would guess closer to 5-7mpg on the highway. Just based on different cars I have had with various rear gears. I am looking for MPG and also less winding of the engine at cruising speed and less wear over time. -C Just can't decide which way to go with my trans decision. Keisler GM O/D or a built 727. I could possibly go the 904 route and get a little better 1st gear ratio, but not sure if they are as tough as the 727. Too many decisions.

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