All Manual transmission cars from 85-96 have the D44 rear axle.
All 84s and all automatics have the D36 rear axle.

RPO Codes:
G92: Performance Rear Axle Ratio, means nothing really.
GU2: 2.73 verts option from 86-93 with G92
15 pinion teeth, 41 ring teeth, 7.875" ring gear outside diameter
GM1: 2.59 standard rear for D36 cars
17 pinion teeth, 44 ring teeth, 7.875" ring gear outside diameter
G44: 3.07 standard rear for 4+3s, option on A4s
3.07:1 ratio: 14 pinion teeth, 43 ring teeth, 7.875" ring gear outside diameter
3.07:1 ratio: 14 pinion teeth, 43 ring teeth, 8.5" ring gear outside diameter (manual transmission)
GW4: 3.31 only for 84s with Z51 only
GT7: 3.33 available on Late-89-90 6speeds
GM3: 3.45 standard rear for later 6speeds
GHO: 3.54 available on early-89 6 speeds, and as an option on a few later years.

Description: Overhung pinion gear
Limited slip differential type: Standard, disc clutches
Drive pinion offset: 1.50" (8.5" ring gear), 1.125" (7.87" ring gear)
Drive pinion type: Hypoid
Number of differential pinions: Two
Pinion/Differential bearing adjustment: Shim
Driving wheel bearing: Tapered roller
Lubricant capacity: 3.75 pt
Lubricant type recommended: GL-5 gear lubricant
Lubricant SAE viscosity: 75W-90

Dana Corp says that the factory gear oil is adequate, but synthetics are superior especially when heat is an issue. A limited slip additive should always be used. (2 bottles) Gear oil should have a GL-5 rating and a 75w-140 or 75w-90 weight, with 75w-140 being the preferred weight.

D44=8.5" ring gear
D36=7, 9/16" ring gear, some books list it as 7.75"
More D44 & D36 specs and replacement parts
Output Torque Ratings-
Max Continuous- 36=850 lbs-ft 44=1,100 lbs-ft
Max Short Duration- 36=2,800 lbs-ft 44=3,460 lbs-ft
Ring Gear Bolts and Size- 10 x 3/8 in.(both)
Pinion Shaft Max Diameter- 1.375 in.(both)

D36+batwing weighs 71 pounds/32.2Kg
D44+batwing weighs 77 pounds/35.2Kg

Side by Side comparison, D36 is the old one.





When will they fail?

There is no concrete limit to the amount of power that a rear axle will hold, they will blow when they damn well please. Remember, its not the HP that breaks anything, its your TQ number. The transmission is the same way.

The important specs here are the output torque ratings. It's really all about traction. If the tires let go before the axle reaches it's terminal max short duration load, nothing breaks. Output torque is subject to about a 10 percent safety factor. Remember that engine torque is multiplied by the drivetrain. If you have 330 lbs-ft x a 3.0:1 first gear and a 3.07:1 axle ratio, that's 3,039.3 lbs-ft of potential torque. (Multiply by ~2.0 for a torque converter) If the tires could hold that much, you can see which axle will break first. Fortunately, most tires can't hold that much torque. You can calculate available traction torque using the following formula. You need to have the weight on the rear tires, plus the amount added from weight transfer.

weight on rear tires X COF X tire radius
Traction Torque= __________________________________
12

COF= Coefficient of Friction. For "normal" tires and pavement, use .7 as a "worst-case." For really sticky tires on normal pavement, use .9. For slicks and sticky dragstrip pavement, use 1.0 to 1.5.

Radius= Measure from center of wheel to ground with tire aired up as it will be driven and the car loaded normally.

Sample: 1993 C4 Conv. 3383 lbs, 50-50 weight Dist + 10 percent rear weight transfer (kinda on the high side), 285/40-17 tires (10.7 radius)

1860 X .7 X 10.7
TT= _______________ = 1160.9 lbs-ft
12

So, with that '93, it's engine can generate 340 lbs-ft, first gear of the automatic is 3.06 and the axle ratio is 2.59. That combo generates 2694.6 lbs-ft of potential torque. Because there is some loss of efficiency for various reasons, multiply that by .9 to get 2425 lbs-ft.
The Dana 36 in that car can handle a peak of 2800 lbs-ft and on the street, you can generate 1160.7 lbs-ft of traction torque, so your are very safe. Start plugging higher COF numbers, adding deeper gears, taller tires or more torque to see just how safe you are with all your mods. Ideally, your traction torque must stay well below output torque. Remember that the dynamics of all this is not necessarily linear like the equations. You may be lower or higher because of changes in pavement, etc. You may momentarily exceed the output torque rating of the axle.

Finally, Don't forget those universal joints back there. A 1350 size u-joint is rated for a maximum of 2,260 lbs-ft (ultimate strength), 1240 lbs-ft max short term and just 206 lbs-ft continuous.

However, a D36 should handle a fair amount under street duty, 400-500crank Tq will eventually kill it, but it may last 50,000mi that way. (it could also go after 10K, you cant say) But, if you put race slicks on it to go drag racing, its gonna blow, and probably that day. Drag Radials like Nitto might let it last 10 passes, or it might last 1000 passes, depends on the hookup of the launch.

The Dana 44 with its 8.5" ring gear is essentially equal in strength to the much touted GM 12 bolt. A D44 is usually bulletproof under street duty, and can usually go into the 10 second range in the 1/4 before it goes. The biggest weak spot in them is the drive spindles and the posi-unit. At this point you may want to either cut back your power, or go to a straight axle. IRS is a great thing, but its not made for that kind of power. I know Speed Demon motorsports builds some billet drive spindles that are essentially bulletproof but do come at a substantial price, but are probably worth it to those running serious ET's with their IRS.

Cryo treating the cover and the ring & pinion gears will make the unit much stronger, on both. The ENTIRE diff and drive spindles might also need it.

Going from 2.xx to 3.xx gearing

The 2.xx axles in the D36 are called 2-series gear case, these are not interchangeable with the 3-series case that the 3.07 comes in, so with GM production parts, you cannot change over (in the olden days they used spacers to change over, but i wouldnt do that). However, there are many aftermarket companies that make 3.54, 3.45, 3.73 thick ring rear gears that will fit into the 2-series housing without forcing you to buy a 3-series and the gears on top. 3.73 is the lowest gear ratio that the D36 can deal with to my knowledge.

It would be smart to inspect the posi-clutches and bearings inside and replace them anytime youre in the rear, the thicker ring gear is weaker than the original gear.Not because of the strength of the gears themselves, but due to the flange of the diff case not being in the designed location for that ratio. With the case flange offset further from the point of gear contact, greater than designed leverage is exerted. This is not a serious problem, or one to be concerned with in most cases. Also, the ring gear, stock OR "thick" is not part of the strength concerns of diffs with lower ratios. As gear ratios become lower, the pinion becomes smaller. It is the pinion strength that is the issue.

If you R&R the differential, You should be looking at anywhere between $400.00 and $600.00 or so, for parts professional gear setting labor.

ET gains on L98 and LT1 from changing gears

The L98 engine has such a short powerband that going to a ratio lower than 3.07 is going to be useless. Something like 3.73 with the L98 will probably make your car quicker to 60mph, but slower in the 1/4mi. So you wont be racing any Civics on the hwy. Our powerband only goes to 4800rpm remember. If youre unfortunate enough to have the 2.59s in the automatic, you can switch up to 3.07, but I would do it in a D44 conversion....otherwise youre not getting your money's worth. If youre looking to get that 'umph' off the line, and havent changed your torque converter, that would be a better place to spend your money.

LT1s are a different animal, the short intake runner kills the low-end torque and amplifies the top-end horsepower, which is how the LT1 gets 300hp from a cam profile that isnt that much different from the L98's. These cars come with the pitiful 2.59 gear in an A4 and a decent 3.45 M6 as standard ratios. Most LT1 guys will get .2-.4 in ET from changing to the lower ratios (3.54/3.73 in A4, 4.10 in M6).

With the A4 the drawback is going to be in your gas mileage department, where youre going to take a 2-4mpg hit on the hwy. If you want to get a feel for 3.54s before buying, try running around all day in 3rd gear.

The M6 isnt going to have a big drop, since you now have a use for the ultra-low 6th gear.

Replacing D36 with D44 notes
Conversion from D36=>D44
Gear/MPH calculator
Upgrading for D36
Exotic Muscle Rear end parts