3.50 or 3.70 REAREND?
06-03-2003, 12:22 AM
#1
Heel & Toe
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3.50 or 3.70 REAREND?
I JUST BUILT A NEW MOTOR FOR MY '77. IT SHOULD BE SOMEWHERE
AROUND 400HP. IM RUNNING A 350 TCI TRANS WITH A 308 REAR. I'M INTERESTED TO KNOW WHICH REAREND THE MEMBERS WOULD SUGGEST, THE 350 OR 370? I WOULD LIKE TO BE ABLE TO DO SOME HIGHWAY DRIVEING.
THANKS
CHARLIE C
AROUND 400HP. IM RUNNING A 350 TCI TRANS WITH A 308 REAR. I'M INTERESTED TO KNOW WHICH REAREND THE MEMBERS WOULD SUGGEST, THE 350 OR 370? I WOULD LIKE TO BE ABLE TO DO SOME HIGHWAY DRIVEING.
THANKS
CHARLIE C
06-03-2003, 12:25 AM
#2
Team Owner
Re: 3.50 or 3.70 REAREND? (Charlie C.)
I JUST BUILT A NEW MOTOR FOR MY '77. IT SHOULD BE SOMEWHERE
AROUND 400HP. IM RUNNING A 350 TCI TRANS WITH A 308 REAR. I'M INTERESTED TO KNOW WHICH REAREND THE MEMBERS WOULD SUGGEST, THE 350 OR 370? I WOULD LIKE TO BE ABLE TO DO SOME HIGHWAY DRIVEING.
THANKS
CHARLIE C
AROUND 400HP. IM RUNNING A 350 TCI TRANS WITH A 308 REAR. I'M INTERESTED TO KNOW WHICH REAREND THE MEMBERS WOULD SUGGEST, THE 350 OR 370? I WOULD LIKE TO BE ABLE TO DO SOME HIGHWAY DRIVEING.
THANKS
CHARLIE C
06-03-2003, 12:26 AM
#3
Race Director
Re: 3.50 or 3.70 REAREND? (Charlie C.)
My Silver '68 has a 3.70, which to me is a little tall for highway cruisin'. I think the 3.55 would be much better. My Silver '75 has a 3.36 in it, which to me is one of the best gears for highway and performance you can get. How's the weather up North in Medina? :lol:
06-03-2003, 12:51 AM
#4
Team Owner
Re: 3.50 or 3.70 REAREND? (Paul Borowski)
My Silver '68 has a 3.70, which to me is a little tall for highway cruisin'. I think the 3.55 would be much better. My Silver '75 has a 3.36 in it, which to me is one of the best gears for highway and performance you can get. How's the weather up North in Medina? :lol:
06-03-2003, 01:36 AM
#5
Heel & Toe
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Re: 3.50 or 3.70 REAREND? (Charlie C.)
I'LL CHECK INTO THE 3.36 GEARS, THANKS FOR YOUR HELP. OH YEA,THE WEATHER,IT SUCKS. RAIN RAIN AND MORE RAIN. I HOPE I CAN REMEMBER HOW TO REMOVE MY T-TOPS.
06-03-2003, 07:45 AM
#7
Melting Slicks
Re: 3.50 or 3.70 REAREND? (Charlie C.)
You should check to see how much your trans slips first before you decide on a new rear gear.
The formula is: mph x 336 x rear end ratio / tire diameter.
Here is your rpm if you have a stock size 27" tire at 75 mph:
75 x 336 x 3.08 / 27 = 2875 rpm. This is a total for direct drive/manual trans and does not take into account non-locking torque conv slip. For that you will need to drive 75 mph and note your rpm. For example, if the tach shows 3200, the converter slips 325 rpm at that speed (depending on how accurate your tach is). That's the same reason GM changed the rear end ratio depending on the trans type you pick.
Here are a few #'s
3.36 gear at 75: 3136 rpm
3.55 gear at 75: 3313 rpm
3.73 gear at 75: 3481 rpm
Just add in your slip amount and you are ready to pick a gear
:cheers:
The formula is: mph x 336 x rear end ratio / tire diameter.
Here is your rpm if you have a stock size 27" tire at 75 mph:
75 x 336 x 3.08 / 27 = 2875 rpm. This is a total for direct drive/manual trans and does not take into account non-locking torque conv slip. For that you will need to drive 75 mph and note your rpm. For example, if the tach shows 3200, the converter slips 325 rpm at that speed (depending on how accurate your tach is). That's the same reason GM changed the rear end ratio depending on the trans type you pick.
Here are a few #'s
3.36 gear at 75: 3136 rpm
3.55 gear at 75: 3313 rpm
3.73 gear at 75: 3481 rpm
Just add in your slip amount and you are ready to pick a gear
:cheers:
06-03-2003, 10:36 AM
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Re: 3.50 or 3.70 REAREND? (Charlie C.)
My 3.70 is a bit steep for highway so I would go a 3.55 fi you drive some on the highway or 3.36 if you drive often on the e-way. I am going to a 5 speed o/d tranny is the future to give my the balance I need.
06-03-2003, 10:48 AM
#11
Le Mans Master
Re: 3.50 or 3.70 REAREND? (Fevre)
My 3.70 is a bit steep for highway so I would go a 3.55 fi you drive some on the highway or 3.36 if you drive often on the e-way. I am going to a 5 speed o/d tranny is the future to give my the balance I need.
06-03-2003, 11:09 AM
#12
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Re: 3.50 or 3.70 REAREND? (fauxrs)
My 3.70 is a bit steep for highway so I would go a 3.55 fi you drive some on the highway or 3.36 if you drive often on the e-way. I am going to a 5 speed o/d tranny is the future to give my the balance I need.
My 3.70 was fine on the freeway - drove it on several long trips with no problems, however I did go for an OD eventually, so now I can drive on the socal superspeedways (freeways) and keep up with traffic.
My 3.70 was fine on the freeway - drove it on several long trips with no problems, however I did go for an OD eventually, so now I can drive on the socal superspeedways (freeways) and keep up with traffic.
06-03-2003, 02:58 PM
#13
Melting Slicks
Re: 3.50 or 3.70 REAREND? (Fevre)
Tire diameter makes a difference,if you like tall tires like a 275 60,run with the 3.70's.Even with the 295 50's and my 3.70 rear on the highway I turned 3400 at around 70 mph.Finally went for a 700r4,so the rpms will drop big time.The high rpms tend to act like a traffic cop to keep the speed downon the highway,but give me a back country road and 125 mph comes on like a freight train!
06-03-2003, 03:02 PM
#14
Melting Slicks
Re: 3.50 or 3.70 REAREND? (Charlie C.)
Hey charlie I have a 3.50 and turn 3500RPM at 70MPH what to swap? Just kidding but I am thinking of swapping Tranies and going to an overdrive to lower that engine rpm.
