Da Wiz

I found a rebuilt Dana 36 on E-bay with fresh 3.73 gears and new bearings and guts. I have some questions before I buy this.

1. I have read articles that stated a tenth of a second improvement in quarter mile times for every .2 change in gear ratio. Is it realistic to expect a .5 to .6 reduction quarter times?

2. Are there any differences between the differential when mated to an automatic or standard tranny?

3. Assuming the rebuild was done correctly, what is a good price for this rear end? I am not giving my old gear up as a core.

Input is greatly appreciated. I am not going to go inside the engine, so HP is going to remain in the low 300's. The exhaust is stock because I admire sleepers. All the reading I have done indicates the 36 is stable until you get in the 400+ HP range, and I will continue to run street tires. This is my daily driver that I want to have a little fun with. If I can make the C5's sweat a little on the launch, more the better.

:cheers:

Da Wiz

Come on fellas, I need a little expert opinion here...

:cheers:

CFI-EFI

1) I have never heard that "rule" before, but a half second is not beyond reason. I got a half second from a torque converter.

2) The stick shift cars got the Dana 44 diff assy. The autos (and all 1984's) have the 36. If you presently have a 36, the rebuilt will bolt right in. If you are replacing a 44, you will need the rear cover (batwing). Also you will need the "C" beam from a 36 car. The diff is longer on the 44 and the 44 "C" beam will be too short. Correspondingly, the driveshaft may have to be changed for the same reason. Check for sufficient slip yoke engagement into the trans. 44's have been swapped for 36's and lived with the lesser amount of "slip". You might get away with the shorter shaft.

3) Hard to say. A total, 36 overhaul with new gears, posi, and bearings could run, $500.00- $700.00, as a bench job. Others may have had one done recently, and be better able to comment on price.

It sounds to me that the 36 should hold up fine for your stated usage. Be prepared for a MAJOR difference in cruising rpms and gas milage, as well as acceleration. Good luck, and...

RACE ON!!!


[Modified by CFI-EFI, 8:21 PM 7/7/2003]

Da Wiz

Thanks for the info. Based on charts I have looked at, cruising RPM at 80 will change from 2000 to @ 2400. Around town will not be quite as noticeable.

:cheers:

CFI-EFI

I need some charts like that. You are reasonably expecting a 20% increase in rpms from a 41% change in ratio??? Enjoy your new gears.

RACE ON!!!

Da Wiz

I can dream, can't I? :yesnod: Once they are in, I hope to enjoy the feel of sweat traveling horizontally around to the back of my head when I plant my right foot. That tends to take the pain out of spending so much time at the gas pump. :cheers:

Ramrod92

Terry, if you were turning 2000 rpm at 80, you can now expectto be turning 2980. Mine with 3.54 is 2720. :steering:

Da Wiz

I went to this link to calculate my final drive rpm's. http://corvetteactioncenter.com/tech...ginespeed.html
I used a tire diameter of 26.5 inches, speed of 80 mph, differential of 3.73 and a final drive ratio of .65 I am thinking that is the overdrive ratio in the 4L60E, correct me if I missed the boat.

At any rate, the final RPM came out to @2450 at 80mph. I hope that ends up being close. :cheers:

Da Wiz

Ramrod and CFI,

Thanks for the info. Hey Ramrod, that much, huh?

larrybsp

Been there, done that. I put a 3.73 in my 86 automatic. I switched from 3.07 gears. I went .5 to 1 second slower in my Solo II runs. The lower gears are mis matched with the long tube runner low end torque stock motor. You rev right through the power band and wind up buzzing the motor but not pulling as your well beyond the power band. You also have to change the speedo gear which means taking off the tranny tail shaft. The gears are poorly designed and break often after being installed. Trust me. You will also buzz down the freeway at 3000 rpm at 80 mph. Its like driving a Datsun. After my experience I'd reconsider the 3.73's unless you consider engine work to move the power band to match. :smash: :rolleyes: :D :seeya

tobijohn

DaWiz wrote:
"I used a tire diameter of 26.5 inches, speed of 80 mph, differential of 3.73 and a final drive ratio of .65 I am thinking that is the overdrive ratio in the 4L60E"

I've got a 96 with the 4L6E and it has a final drive ratio of .70 at least according to CAC.(http://www.corvetteactioncenter.com/specs/1996/96specs.html). I don't know enough about these matters to assume it's the same for the 94 but I'd be suprised if it wasn't. I've also got the optional 3.07 gears...


[Modified by tobijohn, 12:50 AM 7/8/2003]

Well, the difference between .65 and .70 in your case only amounts to about 190 rpm, anyway...


[Modified by tobijohn, 1:02 AM 7/8/2003]

mackeyred96

I ran a Dana 36 with 3.73 on the street for years and never had a problem. With an LT1 car you'll be fine.

Da Wiz

Larry, I have heard the same info regarding TPI engines. The LT1 doesn't have the same torque curve, enabling it to take better advantage of the gearing.

Tobi, You are right. The final overdrive ratio is .7 I found several websites that had in depth info on the 4L60E, including some very interesting info on changing gearing ratios so there is not such a drastic falloff from 1st to 2nd.
Here is the link. http://www.gearvendors.com/cg2wd4s.html

I found the info very interesting. Might be something to consider when it comes time for a rebuild...

Glad to hear that Mackey. Did you always have a 3.73 or did you upgrade to it? What were your performance gains?

Finally, still trying to get more info on a fair price.

:cheers:

Ramrod92

Terry, the most Mackey's car would have come with would be the 3.07s. I pretty sure he is using a Dana 44 now with 4.10s. :eek:

NASCAR314

Switched my 96 from 2:59's to 3:73's with no problems.
Automatic trans.
Big help on acceleration.
I do have trouble keeping the rear end burning up tires :lol:

Go for it.

You will need a "Hypertech Power Programmer" or equivilent computer mod. to change the gear size in the computer. No need to change speedometer gear in trans on a 94 or newer.

This is an awesome up-grade :yesnod:

CFI-EFI

My '84 with 255/50/16 BFG drag radials, and stock 3.07" gears cruises at 2400 rpms @ 85 mph. Tire size is important. A few small errors used on the calulations will throw the answer off, significantly. Your second statement is correct. All 700R4's, 4L60's, and 4L60E's, have the .70:1 overdrive ratio. To get the real tire size, mark the tire at the ground, and the ground. Roll (drive) the car any given number of tire revolutions, untill the mark is at the ground, again. Measure the distance between the marks, and divide that distance by the number of revolutions you moved the car. This is your true, loaded, rolling, tire circumference. Dividing by pi (3.1416) gives you the diameter, and further divided by 2 gives you the true, loaded, rolling radius of your tire. Don't depend on the charts from the tire companies. They aren't THAT accurate. The more wheel revolutions you move the car, the more accurate. Technically, one rev is sufficient, but more revs help even out any error in mark placement. Good luck, and...

RACE ON!!!

Fuzzy Dice

I'm running a Dana 36 with 3:73's ....if you have 300+ hp to the rear wheels be careful not to put stickies out back...the 73's hit a lot harder and you'll tear up the 36 at some point...with street tires you should be OK since you will spin a lot which saves your rear end...I run almost 3000 rpm at 80 mph... good luck

Edit.... I forgot to ask you...if you have a Dana 36 presently, why not have 3:73's put in that vs. someone else's rebuilt problem ?


[Modified by Fuzzy Dice, 8:50 PM 7/8/2003]

Da Wiz

Fuzzy,

The 2 series Dana's case is smaller than the 3 series. (2 series = 2.59, 3 series = 3.07, 3.54, 3.73 etc....) I am told I can't put a 3 series gear ratio in a 2 series case.

:cheers:

CFI-EFI

It has to do with the placement of the ring gear flange on the diff case. The aftermarket offers a "thick" gear that will allow such an installation.

RACE ON!!!

fsr402

Da Wiz.
:seeya
I took my 2.59 rear out and bought a D36 3.07 rear off ebay for $250 then I had a shop here by my home put in 3.73 for $450. I love the way the gears pull but I think that if I had to do it again I would go 3.54's.. I tend to drive the highway a lot and the gears, corsa and no cats can get on my nerves.
I did pick up a whole 1.16 in the 1/4 mile with the change.