Rear Gear Question

Mark Yacavone · 09-16-2013, 03:38 PM

Quote:

Originally Posted by njk53

When it comes to rear gearing, I am not the brightest candle on the cake so, I need some help understanding the application of rear gear ratios and what the performance results of different ratios.

For example we are running a 4:56 gear and several people that I have talked to have said we are a bit over geared for our application. The people I have spoken to have said that we should be running a 4:30 gear.
My question is if we go to a 4:30 ratio gear as recommended, what performance gains should I expect? Quicker ET? Faster MPH? Both?
Also, if I changed to a 4:30 gear, does your shift RPM change? How about my 60 foot times?

I would say, if the converter is right..That is, it flashes right around peak torque, then you might see the same 60' but more mph, then maybe gain a little ET down track.
As many here know ..there's only one way to find out for sure.

tj310 · 09-16-2013, 05:04 PM

Powerglide or a 3 spd ? I run approx the same setup 65 Impala wagon 396-325, 400 trans 4.56 gear. If your running a powerglide I suspect you would be better off with more gear 5.57 perhaps ---Trevor

gsa612 · 09-17-2013, 02:47 PM

Something's not right, your trap rpm seems low with 4.56's, I don't know what cam you got. What's the spring pressure? I'm going through at 6700 with.56's with the 94'tire. Mine goes 11 teens on a average day with 1.45 60' in G.(with no ice or lw oil).I found on these motors because of the cyl. heads (105cc) and the lower piston dome require a different set up than a 325-396 in terms of total timing, jetting, cam position, usable rpm. I would try .88's on your car if the springs check out ok. On a side note NHRA's Danny Gracia ran a wagon like yours a while back(80's). I was going through teardown 20+ years ago and he gave me some good advice/tips on the 402 combo lol..

njk53 · 09-17-2013, 04:07 PM

GSA612 you have a PM

ss3011 · 09-17-2013, 04:42 PM

Would you happen to have run the engine on a dyno, and know what the basic HP and Torque curves are ? When you say you have a 4800 stall converter, is that what it flashes to off the starting line ?

njk53 · 09-18-2013, 08:16 AM

I have dyno sheets. Yes the conver flashes @ 4800 at the starting line.

ss3011 · 09-18-2013, 08:54 AM

Just curious what rpm peak torque and peak HP is at. Converter seems pretty tight.

09-16-2013, 05:04 PM	#2
tj310 Member Join Date: Sep 2009 Location: Dresden On. Canada Posts: 460 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear Gear Question Powerglide or a 3 spd ? I run approx the same setup 65 Impala wagon 396-325, 400 trans 4.56 gear. If your running a powerglide I suspect you would be better off with more gear 5.57 perhaps ---Trevor

09-17-2013, 02:47 PM	#3
gsa612 Senior Member Join Date: Jan 2008 Location: 100th Meridian Posts: 569 Likes: 116 Liked 280 Times in 139 Posts	Re: Rear Gear Question Something's not right, your trap rpm seems low with 4.56's, I don't know what cam you got. What's the spring pressure? I'm going through at 6700 with.56's with the 94'tire. Mine goes 11 teens on a average day with 1.45 60' in G.(with no ice or lw oil).I found on these motors because of the cyl. heads (105cc) and the lower piston dome require a different set up than a 325-396 in terms of total timing, jetting, cam position, usable rpm. I would try .88's on your car if the springs check out ok. On a side note NHRA's Danny Gracia ran a wagon like yours a while back(80's). I was going through teardown 20+ years ago and he gave me some good advice/tips on the 402 combo lol..

09-17-2013, 04:07 PM	#4
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear Gear Question GSA612 you have a PM __________________ Nelson Kowal Stock 345

09-17-2013, 04:42 PM	#5
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 909 Likes: 70 Liked 239 Times in 114 Posts	Re: Rear Gear Question Would you happen to have run the engine on a dyno, and know what the basic HP and Torque curves are ? When you say you have a 4800 stall converter, is that what it flashes to off the starting line ?

09-18-2013, 08:16 AM	#6
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	Re: Rear Gear Question I have dyno sheets. Yes the conver flashes @ 4800 at the starting line. __________________ Nelson Kowal Stock 345

09-18-2013, 08:54 AM	#7
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 909 Likes: 70 Liked 239 Times in 114 Posts	Re: Rear Gear Question Just curious what rpm peak torque and peak HP is at. Converter seems pretty tight.