lower gear for rear end ?
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Joined: Jun 2011
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From: Detroit
lower gear for rear end ?
I have read alot of posts about going higher up in the gearing for HP motors. I use my car on the freeway alot and dont plan on making it a hot rod.
Has anyone lowered the ratio and if so how much ?
at about 65 mph i am near 3300 rpm and would like to lower that... alot but i dont have the funds to do a 4L60/700r4 swap and my ring and pinion humm's now.
Thanks
1979
stock 350
stock trans/rear end
Has anyone lowered the ratio and if so how much ?
at about 65 mph i am near 3300 rpm and would like to lower that... alot but i dont have the funds to do a 4L60/700r4 swap and my ring and pinion humm's now.
Thanks
1979
stock 350
stock trans/rear end
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
If your on the freeway alot then yes the simple fix is some 3.08,s or similar if your not hot rodding.....someone before you was looking for a better launch .
My opinion is on this forum someone would surely love to swap you your 411 rear for their highway gears. The hum is probably just asking for some additive.
My opinion is on this forum someone would surely love to swap you your 411 rear for their highway gears. The hum is probably just asking for some additive.
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
IMHO with a stock '79 350 (assume L48) suggest no taller than a 3.36:1 or 3.55:1, or you'll be right back asking what to do because it's such a lame dog out of the hole, even if you don't have any desire to "hot rod".
FWIW, according to my math, at 65 MPH with 255/60R15's...
4.11:1 = 3319 RPM
3.70:1 = 2988 RPM (-331) edited in
3.55:1 = 2867 RPM (-452)
3.36:1 = 2713 RPM (-606)
3.08:1 = 2487 RPM (-832)
Figures above do not include allowance for any transmission slippage.
FWIW, according to my math, at 65 MPH with 255/60R15's...
4.11:1 = 3319 RPM
3.70:1 = 2988 RPM (-331) edited in
3.55:1 = 2867 RPM (-452)
3.36:1 = 2713 RPM (-606)
3.08:1 = 2487 RPM (-832)
Figures above do not include allowance for any transmission slippage.
Last edited by TheSkunkWorks; May 2, 2012 at 07:51 PM.
Thread Starter
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Joined: Jun 2011
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From: Detroit
@gingerbread, I thought the humm was because it didn't know the words... 
@the skunk a 3.08:1 sounds like its up my alley. I have had hot rods and the thing i hated the most was my wife never wanted to take the car, dont get me wrong if it came to a choice.... thats a tough one, but i love the car and would drive it more often even if it was a dog out of the hole.
I think i really need to look closer at the motor/trans drive line. if the numbers are right and i believe they are then its very possible the original set up is long gone. I always thought it was my fault i could not get the car to a flat idle, maybe not....
@the skunk a 3.08:1 sounds like its up my alley. I have had hot rods and the thing i hated the most was my wife never wanted to take the car, dont get me wrong if it came to a choice.... thats a tough one, but i love the car and would drive it more often even if it was a dog out of the hole.
I think i really need to look closer at the motor/trans drive line. if the numbers are right and i believe they are then its very possible the original set up is long gone. I always thought it was my fault i could not get the car to a flat idle, maybe not....
Burning Brakes
Joined: Apr 2007
Posts: 1,039
Likes: 62
From: Kona Hawaii
Save the funds you would spend on a rear gear swap and use it towards an OD swap.You get to keep your hole shot and have OD for the highway.A 200r4 will cost you a little more than a rear gear swap based on a replacement rear end,and you'll have a new trans.That 200r4 will work good with your 4.11 rear gear.200r4 is as close to a bolt-on swap as it gets.Go check out Bowtie Overdrives.....
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
I agree an OD tranny's really your best best, and sounds like the axle is more like a 3.70. Your sitituations a bit different, being your ring & pinion are humming. Doubt additives will help, as usually just for posi clutch pack noise around turns. Sounds more like pinion angle is out, and the rear needs attention. Be aware, ring & pinion work isn't cheap, and probably be wishing OD tranny funds were your only problem. Thinkin' your best bet is locating a good used full 3.08 diff, and swapping the whole thing out. Don't forget to change the speedo gears.
Melting Slicks
Joined: Sep 2004
Posts: 3,227
Likes: 671
From: Northeast
I have a 78 4spd, 3:70 rear, 255/60/15 and at 70 mph my dash tach would read @3400. I since installed an Autometer column tach and now at 70 it reads a steady 3200rpm. Perhaps your tach is off like mine was.
My guess is 3:70 since in 79 the normal options were 3:36, 3:55 & 3:70.
My guess is 3:70 since in 79 the normal options were 3:36, 3:55 & 3:70.
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Thread Starter
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Joined: Jun 2011
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From: Detroit
I have not talked to them yet but http://www.tracyvette.com is 15 min. away. He has been very helpful and good prices on alot of stuff, all my break parts and a few mesc. things. I have been taking it slow in the funds dept. so if i have to run the car like it is this year and maybe look at a trans swap along with a new ring and pinion next year thats ok.
@Vette5.5 I was a proff auto mechanic for almost 20 years and i know what jobs to leave to the guys that do it all the time, and do it well. i did a few ring and pinions but it is not something i would do in the garage. no press no dial indicator not worth it.
@Vette5.5 I was a proff auto mechanic for almost 20 years and i know what jobs to leave to the guys that do it all the time, and do it well. i did a few ring and pinions but it is not something i would do in the garage. no press no dial indicator not worth it.
