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rear gears

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vent69

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it there any rear gears that i can get, but don't have to change to a dana44. ones that you can just swap????
 

Ken

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1987 Z51 Silver Coupe
What do you have? I assume it is an automatic because you mention not wanting to upgrade to a Dana 44.

The 36 will accept up to a 3.55 or so I think. 3.73 and up require a 44 case.

_ken :w
 

John Lupulio

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1988 triple black convetible
:beer
What do you have? I assume it is an automatic because you mention not wanting to upgrade to a Dana 44.

The 36 will accept up to a 3.55 or so I think. 3.73 and up require a 44 case.

_ken :w
I liked to know tech from a company told me that 3.73 that my car wont do over 90 with them gears because dana 36 is limted to what you can put in? yeah automatic
 

John Lupulio

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May 26, 2011
Messages
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Location
Ct
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1988 triple black convetible
it there any rear gears that i can get, but don't have to change to a dana44. ones that you can just swap????

Thought dana 36 your limited to what gears you can put in?
 

John Robinson

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May 3, 2005
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Muncie, Indiana
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1993 Polo Green Coupe
:beer
I liked to know tech from a company told me that 3.73 that my car wont do over 90 with them gears because dana 36 is limted to what you can put in? yeah automatic

Here is the formula to figure how changing the gear ratio will effect the rpm of the engine.

Here is the formula for figuring the rpm for the different gear ratio

RPM=mph x final drive ratio x gear ratio x 336
________________________________________
26

So let’s use the final drive ratio and gear ratio for my 93 for this example

75 x .70 x 2.59 x 336 = 456876 Divided by 26 = 1752 RPM

Now all you have to do is plug in whatever ratio you want

Using a 3.73 instead of a 2.59 will have the following results at 75 MPH the RPM will be 2530 or 778 RPM more per mile.

You can simulate this by dropping the trans into a lower gear that puts the rpm in that range at 75 to see if you would like that on the road.

As others have said the MPG and the traction will be big issues but this would give a lot lower end performance without touching the engine.

If the engine has any miles on it this will increase the piston wear factor by about 7% because of the increase in what is called feet per minute.


Looking at the RPO codes GM offered the following ratios for the Corvette G44 3.07 - GHO 3.54 - GM1 2.59 - GM3 3.45 - GT7 3.33 - GU2 2.73 - and GW4 3.31 If you have the stock differential than you should be able to put any of those gears into it without any problems. Do you know what the RPO code is for what you have in the car now? The codes should be on the lid of the center consul.
 

John Lupulio

Member
Joined
May 26, 2011
Messages
9
Location
Ct
Corvette
1988 triple black convetible
Here is the formula to figure how changing the gear ratio will effect the rpm of the engine.

Here is the formula for figuring the rpm for the different gear ratio

RPM=mph x final drive ratio x gear ratio x 336
________________________________________
26

So let’s use the final drive ratio and gear ratio for my 93 for this example

75 x .70 x 2.59 x 336 = 456876 Divided by 26 = 1752 RPM

Now all you have to do is plug in whatever ratio you want

Using a 3.73 instead of a 2.59 will have the following results at 75 MPH the RPM will be 2530 or 778 RPM more per mile.

You can simulate this by dropping the trans into a lower gear that puts the rpm in that range at 75 to see if you would like that on the road.

As others have said the MPG and the traction will be big issues but this would give a lot lower end performance without touching the engine.

If the engine has any miles on it this will increase the piston wear factor by about 7% because of the increase in what is called feet per minute.
I understand thanks want more performance 65-80
Is going to give me better pick up not wine engine burst of speed at that kick down from overdrive car has 68 k original have k& n filter twin 58mm BBK THATS IT FOR MODS FREE FLOW CAT
 

John Robinson

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Messages
1,555
Location
Muncie, Indiana
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1993 Polo Green Coupe
Difference between the D36 and the D44

Page 2 ofg
Page4of8
Jood set of tools is required for working on these cars. A nice 100+ piece Master Mechanics set from Sears
~'raftsman) is a great start!
Also, you should have:
* A small hand pump for removal and addition of fluids
* Digital Volt Meter (DVM) and test light for debugging electrical glitches.
* 1/2" drive, 17mm allen head socket. This is used to remove the drain and fill plugs on a ZF6spd. These can
be VERY tight.
Differentials:
This topic has been fodder for fights for a long time now! I hope we can clear the air on this subject once and
for all.

In 1985, the Dana D44 was released for use with the manual, ONLY. No automatics came from the factory with D44 rear end. !

In 1984, only the Dana D36 was available. It was used on both manual and automatic cars.
The difference between the two is ring gear size, and the associated strength that comes with a larger ring
gear.
The D36 has a 7.5" ring gear; the 044, an 8.5" ring gear.
The maximum ratio that will fit in a 036 is a nominal 3.73. After that, your taking your rear ends life into your
~ own hands. The D36 has a power limit of about 450hp ... but it won't last long on the strip, even then ...
The maximum ratio for a 044 is a nominal 4:11. It will require some minor case machining to make it fit
perfectly. The D44 is known to deal with over 650hp with no problems.
When drag racinq, especially when, the power levels get over about 600hp, the independant rear end becomes
a handicap. At this polnt, it might be worth looking into a 4-link live axle setup, if this is the case, a Ford 9" is
the best piece for the job.
At the time of this writing, a D44 is worth about $2000.00, complete (differential, casing, drives haft and
batwing).
The best ujoints are the Spicer units.
As mentioned above (see Fluids), use two bottles of Differential Additive before adding the gear oil. This
recommendation comes from Gordon Killebrew.
* 2.59 is the standard ratio for all automatics, RPO GM1.
* 3.07 is an option, G44, but was standard for 85-88 L98 manuals.
* 3.45 is the standard rear for ZF6 LT1s, with 3.54 an option in early years only.


As for someone telling you a 3.73 would limit you to 90 MPH top speed. Take and divide from my earlier calculations the 2540 RPM at 75 MPH which = 33.8 MPH per thousand RPM take 33.8 x 5000 RPM = 169 MPH. That is in theory assuming you could pull the final drive ratio of .70 in overdrive which you can not. If you could pull 4500 RPM then you would be in the 135 MPH range for top end. But asyou say you are only interested in the 65 to 80 range so yes the 3.73 would give you more performance in that range.
 
Joined
Oct 7, 2007
Messages
719
Location
Amherst, NY
I've owned a 1988 with automatic and stock 2.54 rear axle. Today, I own a 1989 with automatic and the HP 3.07 rear axle. The get up and go is night and day with only a 1 to 1.5 drop in MPGs at 60 MPH. If you run any higher than 3.07, you are going to run into traction issues running stock tires even with a stock engine. I've run several tests using a G-Tech Pro Performance meter, and a full tank is a must to optimize tire traction with a 3.07 axle. The 2.54 would run the 1/4 mile around 15.3 seconds and the 3.07 around 14.7 seconds. These runs were on a smooth road with an incline, so flat road performance would have yielded better results. Both cars were stock with Bosch III injectors. The 2.54 would chirp the tires in 1st (make sure TPS is set correctly), and sometimes going into 2nd. The 3.07 would always spins the tires (10 foot patch is typical), and always chirp going into 2nd (sometimes I could find a 1-2 foot patch of rubber). The 2.54 posted 0-60 MPH in the high 6 seconds, and the 3.07 is the low 6 seconds (traction was limiting better results).
:thumb
 

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