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Rear End Gears

c3cvte

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Feb 23, 2007
Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
Well I think the old girls rear end is wearing out......no not my wife....the Vette.

Wondering if anyone has changed the gears in te rear with lower gears. If I have to replace them I might as well get what I want. 4:11's will be to low but a step under might be nice.

Any experiences or sugestions?
 

Peer81

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May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
No experience only a suggestion..

Our diff's have a 2.87 or 2.72 ratio. If you want to go lower you'll need to change the ring and piniongear, that's if you want to go to a 3.73 or higher. But if you want to change it a ratio lower than 3.73 (example 3.92 or 4.09 etc) you'll also need to change the posi case! (extra $140).

Groeten Peter.
 

c3cvte

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Feb 23, 2007
Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
I think the 3:73 will be the best choice. It will give me the lower gears and when I eventually change out the TH350 for a 700R4 I will have the best of both worlds.

Any thoughts?
 

black_81_vette

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Dec 1, 2002
Messages
295
Location
wisconsin
Corvette
black 81 corvette 4-speed
I run 3.54 gears in mine with a 4 speed manual. Do yourself a big favor and get the\ dana gears, the reason is most of these gearsets are made overseas and do not run very quiet and or dont setup as well as the spicer gear sets.I had a set of motive gear gears and had them took out (noise) and went with the dana set, much quieter and better quaility. Also as a side note our cars have a dana 44 style rear end and jeep and even ford used this style of rear end and gear sets will be cheaper from non corvette part sources.
 

c3cvte

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Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
Well Im not versed very well on rear ends and transmissions so this is definatly a learning experience.

Are you saying to look for a set of gears for a Jeep Dana 44 and that will fit perfectly in my Vette?
 

Peer81

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May 21, 2003
Messages
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Location
Netherlands
Corvette
'81 Black
Also do some research on what ratio would be the perfect first year. From what I've read on forums the 700R4 has a 3.06 first and with a 3.73 diff the total for first would be 11.4:1. Then your first gear is so short that you almost can't use it and shifting from 1 to second will take more time then you win with the very short first. The ideal first gear would be 10:1 ratio, so the diff would have a ratio of 3.26 (that would be a 3.31).
Also what you win in the bottom you lose at the top. I don't know what the speedlimit is overhere but we have a 75mph speedlimit so it also makes a difference if you drive a constant 2100 or 2500rpm.

Also for the Dana44, the handshifted c4's also have (a better) Dana44 and I don't know if you can changes things out with that one, it has the same name but isn't the same diff!

Groeten Peter.
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
I have in my Gail 3.31:1 gears in the differential with the stock TH350C

To give you an example, when traveling at 72 MPH, it spins the engine at 3,000 rpm. Not too bad.

Last Sunday I did a 100 mile round-robin combining about 1/3 each of city driving, freeway, and country roads, and I got 20 miles per gallon.:upthumbs
 

c3cvte

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Joined
Feb 23, 2007
Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
I'm not to concerned about gas milage. Not really a long road trip type of vehicle anyway and mostly just around here. But I do worry about twisting the engine at too many RPM's for an extended period of time.

I have looked into the Jeep Gears and have a few calls into some places but I'm finding that my lack of knowledge is really getting in the way. Its fun to learn about new things but frustrating at the same time. I just don't want to learn the wrong way about something I should NOT use. I don't want to buy the wrong thing and it not work. Once I think I have it narrowed down I will post what I think I need and maybe I can get some comments on that.
 

c3cvte

Active member
Joined
Feb 23, 2007
Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
Ok Heres what I have found out so far

Im looking at getting the rebuilt 3.70 Dana 44 differential from Ecklers for $899.99.

Questions now that I have are....

#1. Is this a good deal? I really dont want to yard something out of a junk yard, rebuild it myself (I have never done this) and put it in not knowing how good it really is.

#2. What parts need/should be replaced when I replace the differential? Bearings, U-Joints, Rear end bushings......

Just would like to get a realistic parts list so I dont have to climb out from underneath the car to order the parts and wait 2 weeks for it to show up.

Any help or advice would be greatly appreciated.
 

c3cvte

Active member
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Feb 23, 2007
Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
Ok so now I think it is rear bearings. Pulled it out of the garage and it was doing fine. Then took a corner and heard "snaping" comming from the rear wheel. I pulled over and drove it back and forth in a parking lot with the door open and my head hanging out and it sounds like its comming directly from the wheel and not from underneath the car.

So I looked through my repair manual and they have a complicated process for replacing/adjusting bearings.

My question is....is it as complicated as it seams? Is this something I should take to my mechanic because it requires specialized tools or can I do this in my garage?
 

Rowdy1

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Mar 26, 2001
Messages
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Location
Lake Hopatcong, NJ
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1962 CORVETTE-SOLD 2004 Z16 Z06 CE
Sounds Like..........

A universal joint, check all of them for rust, excessive play etc.
 

Tom Bryant

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Edgerton, Ohio, United States
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1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
What Rowdy said. Sounds like a u-joint to me too. Plus they are the easiest thing to check and replace if necessary.

As for rear gears the 700R4 has a very low 1st gear so you don't have to go as low on the rear end gear. Without doing the math I'd estimate that a 700R4 with a 3.55 rear gear would be close to a turbo 350 and a 4.11 or maybe between a 3.73 and 4.11. If you go too low in the rear your 1st gear will be used up as soon as you hit the gas with a 700R4. Do some figuring before you select rear gears if your plan is to go 700R4 eventually.

Tom
 

c3cvte

Active member
Joined
Feb 23, 2007
Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
Well Visual inspection of the U-joints show they are ok. Nothing out of the ordinary. One weird thing was when under the car I would rotate the wheel back and forth the inch or so until they caught. I was looking for issues with the u-joints. The weird thing was that I could turn the drivers side tire and feel it catch....then if I pushed harder I could get another 1/2" of rotation out of it without the drive axels turning at all. Im worried that might be the bearings spining on the spindel. I'm going to pull the drive axels this weekend and replace the u-joints but thought that I shouldnt be able to rotate the tire that additional 1/2". The pass side doesnt do it. Any thoughts on that?
 

schweng18

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Jan 22, 2006
Messages
55
Location
Bismarck, ND
Corvette
81 Frost Biege
One easy way to check and see if the bearing is going bad. Drive the car for a short distance and cautiously feel the rim by the lugnuts. If it is hot in comparison to the other rims, odds are that the bearing is bad. When mine went out I removed the entire trailing arm assembly and send it in to be rebuilt.
 

Evolution1980

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Cleveland, Ohio
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ZZ4, 700R4, Steeroids rack & pinion, VB&P Brakes
ya kinda got two separate ideas/questions going here in this thread, but I may be able to impart a little bit of info regarding the possible future swap to a 700R4.

If the '81 had the same rear as the '80 (3.08 gears), then swapping the TH350 for a 700R4 will essentially give you a 3.73 first gear due to the different gearing of the 700R4 first gear. Taking your rear end to something like a 3.73 and then going to a 700R4 will increase that first gear difference even more so.

Beyond that, I'm not the best person to give answers regarding the differences in transmissions and rear ends. :)
 

c3cvte

Active member
Joined
Feb 23, 2007
Messages
37
Location
Olympia Washington
Corvette
1972 Stingray
Beyond that, I'm not the best person to give answers regarding the differences in transmissions and rear ends. :)

Well as far as I see I have been getting a lot of good advice. The Idea of going to 3:73 or around there is not the best idea with an eventual 700R4 install. I would have a hell of a launch in first gear but I would be shifting into 2nd at about 15mph. Not what Im really looking for. I have to find the gear calculator that everyone references (I found it once before but now cant find it for anything) to really decide on what I want to do.

Im confused as hell on what the clunking noise is under the car. Every time I put it up on jack stands I cant get it to make the noise (I figured it was because the suspension being out of wack) and when I drop it back down it doesnt make the noise for awhile. Stumped!
 

Evolution1980

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4,302
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Cleveland, Ohio
Corvette
ZZ4, 700R4, Steeroids rack & pinion, VB&P Brakes
I'm going to pull the drive axles this weekend and replace the u-joints...
Might want to do an advanced search in the forums here, limiting your search to the C3 section. I recall there has been good conversations about replacing the u-joints and what the best brands are versus some garbage brands. "Spicer" or something seems to ring a bell as the preferred mfg. But check for yourself...(if ya care. :))

I'm confused as hell on what the clunking noise is under the car. Every time I put it up on jack stands I cant get it to make the noise (I figured it was because the suspension being out of wack) and when I drop it back down it doesnt make the noise for awhile. Stumped!
Sure still sounds like u-joint issues. Although the bearings, as mentioned earlier could also be suspect. I know my u-joints were shot when I got my car with 60K+ miles. And the bearings weren't long after that before they started actually smoking while I was driving down the highway! :eek:hnoes
 

Tom Bryant

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1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
I have to find the gear calculator that everyone references (I found it once before but now cant find it for anything) to really decide on what I want to do.


At the top of the page click on Tech Center then Tool Box.

Tom
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
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1981 HD Suspension; ZN1 Option
...Im confused as hell on what the clunking noise is under the car. Every time I put it up on jack stands I cant get it to make the noise (I figured it was because the suspension being out of wack) and when I drop it back down it doesnt make the noise for awhile. Stumped!

C3,

Have you checked the rear spring holding bolts? I had a clunk sound at one time, and I found the rear spring front short bolt missing. I also had the lower center rubber mount broken. I am not sure which gave way first and cause the other, but its worth checking.

The short bolt fits through the rear "Y" pipe heat shield, so it is easy to miss. ;shrug
 

Evolution1980

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Messages
4,302
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Cleveland, Ohio
Corvette
ZZ4, 700R4, Steeroids rack & pinion, VB&P Brakes
Hey C3..."I was just thinking..." (yeah, insert joke here...)

When does this clunking sound happen? Only when you put the car in gear? What about when shifting?
If you manually keep the car in -2-, take it to high RPM's, let off the throttle and then shift into -D-, does it clunk? If so, I am 99% certain I know what your problem is...
 

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