’89-10 Dana 60 rear end

[Corvettes White]

’89-10 Dana 60 rear end

Here is a photo of a ZR-1 Dana 60. GM appears to have cast a special housing for this car. It bolts right up to the C-beam bridging forward to the transmission tailshaft. However, the batwing is completely different other than the bolt patterning being the same. The yokes coming out of the case are different length left and right. So the half shafts would also be different lengths. I am guessing to deal with torque steer. Other than adapting the yokes somehow the main case is bolt in.

I have not checked the gear ratios, but the Dana 60 is numerically higher than the Dana 44 that came out of my ’89 L98 car. So I would think the tune in the chip is adjusted.

Any thoughts out there about using the 60 or the 44 in a street driven car?

BTW This is not an active car rear end. The third photo is of one of those.

George

[LGAFF]

Didn't the prototypes have 3.54 vs the 3.45?

[Corvettes White]

I measured it, carefully. 3:54 George.

[WVZR-1]

It would be interesting to remove the cover and post the ring gear information from the gear. Snapshots are sometimes deceptive but that housing doesn't appear to be tall enough to house a 248mm ring gear. What is the height of the rear top of cover to bottom of cover.

[Hog]

Didn't the prototypes have 3.54 vs the 3.45?

Wasnt there Export-Europe ZR-1's that got the 3.54's vs 3.45's?

[WVZR-1]

Wasnt there Export-Europe ZR-1's that got the 3.54's vs 3.45's?

CQX is a 3.54 ratio axle code that shows production through '92. There are reports of random cars with 3.54 and I believe a few of those have been reported as ZR1's - '91 comes to mind. I don't believe that all exports got the 3.54 and certainly anything after '92 certainly judging from service parts information didn't get the 3.54 package.

[Hog]

CQX is a 3.54 ratio axle code that shows production through '92. There are reports of random cars with 3.54 and I believe a few of those have been reported as ZR1's - '91 comes to mind. I don't believe that all exports got the 3.54 and certainly anything after '92 certainly judging from service parts information didn't get the 3.54 package.

What I found over on the home page.

3:54 Rear Ends
The following information provided by Gordon Killebrew.

It was originally released for cars going to the European market because of low noise level requirements.
It was not an option you could order. It was automatically a 3.54 axle instead of a 3.45 when going to a Country that required this.
From the start of production in 1988 (MY89) to 01/01/89, all 6-speeds had a 3.54 axle. After 01/01/89 the ZR-1s used a 3.45 axle. The L98 6-speeds used a 3.31 axle. The 3.54 axle was not EPA certified in 90-92 because it went to the European area market. In 1990 the L98 & LT5 6-speeds used a 3.45 except the GHO code with a 8.5 ring gear.
The are no records for how many, and there were no break points. They were produced as ordered.
I doubt that any went to the country of Switzerland due to their noise level requirements. Most ZR1's did not meet their requirements. There were some sent to England.


RPO for 3.45 and 3.54

GH0----Rear Axle, 3.54 Ratio
GM3----Rear Axle, 3.45 Ratio

EXP----Export

A true Dana 60 with its 9-3/4" ring gear would be quite beefy indeed.

[Corvettes White]

Below are the two build sheets for the cars.

First is from the donor '89-L98 car. The car came with a 6-speed. It was also built for Chevy Engineering. 3.54 ratio is listed on the build sheet.

Second is from the donor '89-LT5 car. This car also came with a 3.54.

Now I am just going to need to open up the case that is on the floor of the garage to see what is inside in terms of a Dana 44, Dana 60 or something else. I assume that the rear was installed by the engineering guys after the car went down the assembly line.

George

[Blue Flame Restorations]

Cool stuff, George!

[Corvettes White]

Okay WVZR-1, you called it. I came home a bit early from work today (the 405 freeway sucks at 5:30) and sliced open the two pumpkins. Both had the same ring sets, Dana 44 with 3.54 ratios.

The differences are: that the prototype case is thicker, stiffer that the stock case; the half-shafts are uneven length with constant velocity joints; and the mounting to the chassis of the car is different.

I think I will refit the prototype case with stock half-shafts and install it in the car. The bat wing fits.

The stock case is on the photo on the left.

George

[Hib Halverson]

I am skeptical of Killebrew's information.

Back in the day, I spoke with Corvette development engineers about the 3.54 vs 3.45 debacle, one of them being my old friend, Jim Ingle.

All during development, the 3.54 axle had a noise problem. Chevrolet believed it would be a customer satisfaction problem once cars went on sale and pressed Dana to fix it. Turns out that the noise was inherent with the 3.54 ring-and-pinion's tooth count and, thus, could not be eliminated. Further development discovered a 3.45 ratio, with a different tooth count, could provide virtually the same performance but without the noise.

The idea that 3.54 axles went to countries with noise restrictions is ridiculous. Not only were rear ends with the 3.54 ratio noisier, but cars equipped with them would have noisier exhaust, too, because for a given vehicle speed, engine rpm would be higher.

No saleable ZR-1 was built with a 3.54 axle. Only the prototypes and some pilots got them, but that included some of the cars the media evaluated during the first round of magazine road tests, many of which were done with the '89s.

[Corvettes White]

Well. I got the rear back from the shop. Replaced the constant volocity half shafts with standard ones. Removed the prototype cover and installed a regular prodiction item. 3:54 in an '89. So no complaints. Cross that off the list. Back to the soap and water. George.

[Hog]

I am skeptical of Killebrew's information.

Back in the day, I spoke with Corvette development engineers about the 3.54 vs 3.45 debacle, one of them being my old friend, Jim Ingle.

All during development, the 3.54 axle had a noise problem. Chevrolet believed it would be a customer satisfaction problem once cars went on sale and pressed Dana to fix it. Turns out that the noise was inherent with the 3.54 ring-and-pinion's tooth count and, thus, could not be eliminated. Further development discovered a 3.45 ratio, with a different tooth count, could provide virtually the same performance but without the noise.

The idea that 3.54 axles went to countries with noise restrictions is ridiculous. Not only were rear ends with the 3.54 ratio noisier, but cars equipped with them would have noisier exhaust, too, because for a given vehicle speed, engine rpm would be higher.

No saleable ZR-1 was built with a 3.54 axle. Only the prototypes and some pilots got them, but that included some of the cars the media evaluated during the first round of magazine road tests, many of which were done with the '89s.

The loading of the engine also contributes to exhaust noise, which would be reduced with a lower gear, not rpm/speed alone.

But 3.54 to 3.45 no human ears would be able to tell the difference. __________________

[WVZR-1]

The loading of the engine also contributes to exhaust noise, which would be reduced with a lower gear, not rpm/speed alone.

But 3.54 to 3.45 no human ears would be able to tell the difference. __________________

I can understand an axle ratio change regardless of how minor for "noise abatement" where required. A ratio change is as simple as you or I being able to drive out of drone. The vehicle is evaluated at a specific spec determined by the country of destination. Export exhaust was seldom the same as production for many US productions heading elsewhere.

Maybe substantiating Hib's comments was the change to 3.33 ratio in the M6 cars during C4 production in '89. '90 L98 cars got these also. Hib's reference to noise I'm sure had nothing to do with noise abatement but a drive-line issue as he mentions a tooth count issue. The Corvette 3.54 was a 46/13 combination but years later the 3.55 as a 39/11 tooth count returned to the Dana 44HD. Seems to maybe hint there was likely an issue with the original 3.54.

GM SPO shows axle codes in '90 only for the 3.33 and the 3.45 but then mix '91 & '92 production codes into one chart and again mention 3.45 and 3.54 but no 3.33 references. '91 & '92 3.45 CQR(GM3) and 3.54 CQX(GH0). An SPO error? Maybe.