Which way? Change diff ratio to 3:55 or change engine to 383?
#1
Melting Slicks
Thread Starter
Which way? Change diff ratio to 3:55 or change engine to 383?
Currently running very mild SBC with 200R4 trans and 3:08 rear ratio. I need to decide whether to change the diff ratio now and buy another block and start building a 383 or not worry about the diff as I have been told that a 383 would be fine with the 3:08 The current stall in the torque convertor is 1800 - 2100 and I would want to build the motor for torque not concerned too much with hp.
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
#3
Le Mans Master
Member Since: May 2002
Location: Lebanon Township New Jersey
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Any engine will accelerate quicker with 3.55 gears than with 3.08 gears. Its pure physics. The question is whether that is important to you. When I changed from 3.08s to 3.73 gears in my car, with the same 383 engine, I took almost 5 tenths off my 1/4 mile ET.
#4
Pro
Depending on what you want out of the car I would change the rear ratio to 3:55 or 3:73 first and see how you like it.
Changing gears is much more cost effective than building an engine. The only down side is the increased RPM at highway speeds and higher fuel consumption.
In the end even if you do decide to build a 383 then it will not need to have as much hp/tq to give you the desired acceleration if your gears have already been changed. JMHO...
Changing gears is much more cost effective than building an engine. The only down side is the increased RPM at highway speeds and higher fuel consumption.
In the end even if you do decide to build a 383 then it will not need to have as much hp/tq to give you the desired acceleration if your gears have already been changed. JMHO...
Currently running very mild SBC with 200R4 trans and 3:08 rear ratio. I need to decide whether to change the diff ratio now and buy another block and start building a 383 or not worry about the diff as I have been told that a 383 would be fine with the 3:08 The current stall in the torque convertor is 1800 - 2100 and I would want to build the motor for torque not concerned too much with hp.
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
#5
Melting Slicks
Thread Starter
Long term I want to upgrade the engine but it is functioning well just low on power so no need to hurry with it. The big thing is whether the 383 will be happy chugging along at 1600 rpm at 60 mph. The 350 will do it but it doesn't take much of an incline to force a downshift or at least disengaging the lockup. Leaning toward the diff change to get to 2000 rpm at 60 mph. Not looking forward to the diff rebuild though, have never done one before.
#6
Burning Brakes
The 200R4 ratios are 2.74, 1.57, 1.00 and 0.67
With your 3.08 diff ratio that makes it 8.44:1 in 1st gear, and 2.06:1 overall in overdrive!
Any increase in cubic capacity will give you the opportunity to gain more torque to pull that tall gearing, but it won't be ideal.
Yes, with the appropriate build (truck engine specs) a 383 will be happy to run at 1600 rpm in overdrive.... but is that what you really want?
Put in a 3.73 ratio diff now, and you will immediately get a gain in performance.
1st gear will be 10.2:1 which is ideal for take off, and OD will be 2.5:1 which will let the motor cruise nicely at 2000 rpm at 60 mph.
The gearing change may be all that's needed to satisfy you.
If not, the 3.73 diff also allows you more options for a much more powerful stroker motor in the future.
Getting the gearing right makes a huge difference in driving enjoyment.
cheers
With your 3.08 diff ratio that makes it 8.44:1 in 1st gear, and 2.06:1 overall in overdrive!
Any increase in cubic capacity will give you the opportunity to gain more torque to pull that tall gearing, but it won't be ideal.
Yes, with the appropriate build (truck engine specs) a 383 will be happy to run at 1600 rpm in overdrive.... but is that what you really want?
Put in a 3.73 ratio diff now, and you will immediately get a gain in performance.
1st gear will be 10.2:1 which is ideal for take off, and OD will be 2.5:1 which will let the motor cruise nicely at 2000 rpm at 60 mph.
The gearing change may be all that's needed to satisfy you.
If not, the 3.73 diff also allows you more options for a much more powerful stroker motor in the future.
Getting the gearing right makes a huge difference in driving enjoyment.
cheers
#8
Safety Car
Currently running very mild SBC with 200R4 trans and 3:08 rear ratio. I need to decide whether to change the diff ratio now and buy another block and start building a 383 or not worry about the diff as I have been told that a 383 would be fine with the 3:08 The current stall in the torque convertor is 1800 - 2100 and I would want to build the motor for torque not concerned too much with hp.
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
DO MA NEU!
#10
Currently running very mild SBC with 200R4 trans and 3:08 rear ratio. I need to decide whether to change the diff ratio now and buy another block and start building a 383 or not worry about the diff as I have been told that a 383 would be fine with the 3:08 The current stall in the torque convertor is 1800 - 2100 and I would want to build the motor for torque not concerned too much with hp.
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
I'd like to recycle the Performer intake and the shorty headers to keep costs down but the old Holley I would probably change to a Quickfuel. Nothing much is original on this car so I don't mind changing things around a bit.
Suggestions?
1978 corvette started as a stock L48 Auto TH350 stock torque converter and 3.08 Rear. Made the change to a GMZZ383.
My plan was to change both the engine and transmission at the same time. I was looking for a richmond 6 speed with a 5th gear 1:1 this would make up for the 3.08 rear. The problem I ran into they stopped making the richmond 6 speed with 5th 1:1 so I decided to only do the engine this summer and make the transmission a winter project. Next tranny in line is the T56 close ratio.
As for how the car runs now, it depends on who you speak to. For a daily driver it's ok and is much more fun to drive. With the stock torque converter and a TH350 and a 3.08 it makes it near impossible to get everything from the ZZ383. eg 1/4 runs. The stock TH350 shifts @ 4500-4800 at WOT, you have 3 average gears with a 3.08 my ZZ383 pulls great starting at 2500 and never gets close to 5500 RPM ever unless I lock it down in 1st or 2nd and manual shift the tranny.
It cannot spin my tires 245 x 18 supersports. Lauches with 7.2 G's which almost matches my 2010 GS auto, My final goal is to match the C6 ratio's which the T56 close ratio + 3.73 rear is very close to.
I my self started at the engine which made a very noticable improvement with expected disapointments, tranny next , rear last.
If you plan to keep the 200R4 I would start with the engine / Torque converter and then do the rear. The engine swap + torque converter will be very noticable, and the rear change only will leave you asking for more acceleration.
#11
Melting Slicks
Thread Starter
I vote both. I'm firm believer that the camshaft needs to be matched to both the stall speed of the converter and the rear gearing. Building a 383 with lower the rpm range of what ever camshaft you decide to use by about 400 rpm and the gearing would be determined by how rowdy the build was.
DO MA NEU!
DO MA NEU!
#12
Le Mans Master
I just installed a ZZ383 (new version with 450hp/450/tq) and ran for a week or so with a 3.73 rear. Since I already had a 383 in it was just a difference of where the hp/tq came in. A week later I was offered a 3.36 from a friend who had sold his shop a few yrs ago and didn't use the gear for a planned project after rebuilding it. For cruising the 3.36 is great as it is still fun off the line but I can drive all day long at 1800 rpm @ 50 mph. I have put about 900 miles on it and will stick with the 3.36. I don't think that I would have been happy moving to a 3.08. Where I live the hiways are all 50 mph so no need for a T56. With the 3.36 I avg'd 18.3 mpg when at the 500 mi break in oil change. At 900 I am just above 19 mpg. I just dropped an Edel 750 cab on it that I had with no tuning done to it as I will be replacing it next spring.
I would swap in the gears first then if you still want to add the 383.
I would swap in the gears first then if you still want to add the 383.
Last edited by gdh; 09-24-2014 at 08:10 AM.
#13
Race Director
The 200R4 ratios are 2.74, 1.57, 1.00 and 0.67
With your 3.08 diff ratio that makes it 8.44:1 in 1st gear, and 2.06:1 overall in overdrive!
Any increase in cubic capacity will give you the opportunity to gain more torque to pull that tall gearing, but it won't be ideal.
Yes, with the appropriate build (truck engine specs) a 383 will be happy to run at 1600 rpm in overdrive.... but is that what you really want?
Put in a 3.73 ratio diff now, and you will immediately get a gain in performance.
1st gear will be 10.2:1 which is ideal for take off, and OD will be 2.5:1 which will let the motor cruise nicely at 2000 rpm at 60 mph.
The gearing change may be all that's needed to satisfy you.
If not, the 3.73 diff also allows you more options for a much more powerful stroker motor in the future.
Getting the gearing right makes a huge difference in driving enjoyment.
cheers
With your 3.08 diff ratio that makes it 8.44:1 in 1st gear, and 2.06:1 overall in overdrive!
Any increase in cubic capacity will give you the opportunity to gain more torque to pull that tall gearing, but it won't be ideal.
Yes, with the appropriate build (truck engine specs) a 383 will be happy to run at 1600 rpm in overdrive.... but is that what you really want?
Put in a 3.73 ratio diff now, and you will immediately get a gain in performance.
1st gear will be 10.2:1 which is ideal for take off, and OD will be 2.5:1 which will let the motor cruise nicely at 2000 rpm at 60 mph.
The gearing change may be all that's needed to satisfy you.
If not, the 3.73 diff also allows you more options for a much more powerful stroker motor in the future.
Getting the gearing right makes a huge difference in driving enjoyment.
cheers
Last edited by 63mako; 09-24-2014 at 09:29 AM.
#14
Race Director
#15
Melting Slicks
I agree with what mako says above.
I had my diff rebuilt stock. Then started building an engine. This soon took on a life of its own, and now my diff is probably a little weak for the engine, and will have to be upgraded to a super 10 or a 12 bolt sooner rather than later.
Oh well, it's just money.
Carter
I had my diff rebuilt stock. Then started building an engine. This soon took on a life of its own, and now my diff is probably a little weak for the engine, and will have to be upgraded to a super 10 or a 12 bolt sooner rather than later.
Oh well, it's just money.
Carter
#18
I hate to see other people think that they could get better fuel mileage from changing thier gear ratio from a 3.08 to a 3.73, The overdrive is what actually gave you the better fuel milage, not the gear ratio change.
#19
Safety Car
DO MA NEU!
#20
Le Mans Master
Bluedawg and a few others have made very good points. You really need to know what you want out of this engine ie. A 1/4 mi screamer, a fun cruiser a litlle of both. Each engine will have some different components like cam, intake and heads. When they talk about matching your components it is for where you want the power to come in at your tq and hp curve). My last engine was built more with 1/4's in mind so the cam, single plane intake, headers, mufflers, carb and heads were purchase with that intent where the power band was from 4500 - 7500 rpm. This engine just screamed, sent many a C5Z and C6Z to speed shops as they would fall behind that old C3 convertible once we hit the highway. Given that I would go on some cruises as well I didn't want it so high strung that it just wasn't any fun on the street. So there was a bit of a compromise in picking the cam. The GM ZZ383 I swapped in met my needs in that I am no longer taking the '72 to the track, I wanted a fun cruiser. The 450 hits max @ 4500 which is fine for what my needs for this engine are. With swapping in the 3.36 rear it still gets sideways fast. The car feels fast at lower rpm around the street but the other engine would walk all over the new one at the track.
Spend a lot of time identifying what how you are going to spend most of your time in the car. This will help determine what components you should build into your engine. You need to plan from carb to tail pipe in looking at matching components with your desired results keeping budget in mind.
Spend a lot of time identifying what how you are going to spend most of your time in the car. This will help determine what components you should build into your engine. You need to plan from carb to tail pipe in looking at matching components with your desired results keeping budget in mind.