78/80 IRS Interchange
Thread Starter
Advanced
Joined: Aug 2012
Posts: 55
Likes: 1
78/80 IRS Interchange
I plan on removing the complete 1978 IRS from my donor Vette, reconditioning it, and installing it into my 1980. Then I would like to install the 80 IRS as is into the 78 donor car to enable limited driveability until I install a solid axle 9 inch Ford into the 80 for drag racing which I can't do until the Spring of 2014. I'd rather not keep the batwing in the 80 and exchange differentials. Can anyone help with a description of the major steps involved to first do the 78 install?
Safety Car
Joined: Nov 2008
Posts: 3,717
Likes: 551
From: Seattle Washington
Yes what You are wanting to do can be done, but the fabrication involved to do only to do it all over again for a solid rear I think will change you mind. The 78 Iron Pumpkin can be mated to the 80' batwing, no adapter needed.Two of the Bolt holes won't line up so don't use them. You will also need to switch some of the Control Arm parts. Assuming the 80 is an Auto the 1/2 shaft U-Joints are going to be diffrent and You will need to switch the 1/2 shafts and the out side Flanges to. As far as putting the 80' in the 78, I would think that everything should be able to go the other way around. The other way to do it is to Weld new Mounts on both frames to switch both Rear's as complete units.
Thread Starter
Advanced
Joined: Aug 2012
Posts: 55
Likes: 1
It sounds like there will be more work to use the 78 pumpkin on the 80 batwing. That is one of the reasons I would like to exchange the complete suspension. I think that the only thing left to do would be to weld new brackets to the 80 frame to mount the crossmember. Correct me if I'm wrong. I might have to have a different length driveshaft made?
This a fine point, but there is a typo in my original post. I'm going to put the 9 inch into the 78, not the 80, so there will not be double work to the 80. The correct version is:
I plan on removing the complete 1978 IRS from my donor Vette, reconditioning it, and installing it into my 1980. Then I would like to install the 80 IRS as is into the 78 donor car to enable limited driveability until I install a solid axle 9 inch Ford into the 78 for drag racing which I can't do until the Spring of 2014. I'd rather not keep the batwing in the 80 and exchange differentials. Can anyone help with a description of the major steps involved to first do the 78 install?
This a fine point, but there is a typo in my original post. I'm going to put the 9 inch into the 78, not the 80, so there will not be double work to the 80. The correct version is:
I plan on removing the complete 1978 IRS from my donor Vette, reconditioning it, and installing it into my 1980. Then I would like to install the 80 IRS as is into the 78 donor car to enable limited driveability until I install a solid axle 9 inch Ford into the 78 for drag racing which I can't do until the Spring of 2014. I'd rather not keep the batwing in the 80 and exchange differentials. Can anyone help with a description of the major steps involved to first do the 78 install?
Last edited by Last Special; Jun 15, 2013 at 11:48 AM.
Safety Car
Joined: Nov 2008
Posts: 3,717
Likes: 551
From: Seattle Washington
It sounds like there will be more work to use the 78 pumpkin on the 80 batwing. That is one of the reasons I would like to exchange the complete suspension. I think that the only thing left to do would be to weld new brackets to the 80 frame to mount the crossmember. Correct me if I'm wrong. I might have to have a different length driveshaft made?
This a fine point, but there is a typo in my original post. I'm going to put the 9 inch into the 78, not the 80, so there will not be double work to the 80. The correct version is:
I plan on removing the complete 1978 IRS from my donor Vette, reconditioning it, and installing it into my 1980. Then I would like to install the 80 IRS as is into the 78 donor car to enable limited driveability until I install a solid axle 9 inch Ford into the 78 for drag racing which I can't do until the Spring of 2014. I'd rather not keep the batwing in the 80 and exchange differentials. Can anyone help with a description of the major steps involved to first do the 78 install?
This a fine point, but there is a typo in my original post. I'm going to put the 9 inch into the 78, not the 80, so there will not be double work to the 80. The correct version is:
I plan on removing the complete 1978 IRS from my donor Vette, reconditioning it, and installing it into my 1980. Then I would like to install the 80 IRS as is into the 78 donor car to enable limited driveability until I install a solid axle 9 inch Ford into the 78 for drag racing which I can't do until the Spring of 2014. I'd rather not keep the batwing in the 80 and exchange differentials. Can anyone help with a description of the major steps involved to first do the 78 install?
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
I second the motion to bolt the iron 10-bolt IRS hoghead onto the batwing for your '78. FWIW, I bought a batwing specifically for mating to my '78 shark's 12-bolt IRS diff, on purpose. Yes, I did say 12-bolt IRS diff, for those not familiar with driveline options for severe duty applications other than a live axle.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Advanced
Joined: Aug 2012
Posts: 55
Likes: 1
Since my last post, I discovered a bad wheel spindle bearing on the '80, so I won't be able to simply interchange it with the '78 without rebuilding it. After the suggestions from the forum, my plans will brobably have to change. Now, I'd like to store the '80 IRS but keeping the batwing, so I could bolt the entire '78 IRS except for its frame mounting crossmember. The '80 would then have
1. '80 batwing
2. '78 pumpkin, control arms, wheel assemblies, struts, half shafts, shocks and u-joints.
The '78 would be stored, waiting for the solid axle.
Would this appproach work? Any comments or suggestions would be greatly appreciated.
Thanks, Ric
1. '80 batwing
2. '78 pumpkin, control arms, wheel assemblies, struts, half shafts, shocks and u-joints.
The '78 would be stored, waiting for the solid axle.
Would this appproach work? Any comments or suggestions would be greatly appreciated.
Thanks, Ric
Last edited by Last Special; Jun 22, 2013 at 12:25 PM. Reason: To improve clarity.
Melting Slicks
Joined: Jun 2003
Posts: 2,802
Likes: 241
From: Niles, MI
You may want to read this thread before you start.
Bee Jay Aluminum Rear End Conversion
If you put an early cast iron diff on a later model with a bat wing, your pinion mount hole will be off location by 1/2".
Bee Jay Aluminum Rear End Conversion
If you put an early cast iron diff on a later model with a bat wing, your pinion mount hole will be off location by 1/2".
Safety Car
Joined: Nov 2008
Posts: 3,717
Likes: 551
From: Seattle Washington
Since my last post, I discovered a bad wheel spindle bearing on the '80, so I won't be able to simply interchange it with the '78 without rebuilding it. After the suggestions from the forum, my plans will brobably have to change. Now, I'd like to store the '80 IRS but keeping the batwing, so I could bolt the entire '78 IRS except for its frame mounting crossmember. The '80 would then have
1. '80 batwing
2. '78 pumpkin, control arms, wheel assemblies, struts, half shafts, shocks and u-joints.
The '78 would be stored, waiting for the solid axle.
Would this appproach work? Any comments or suggestions would be greatly appreciated.
Thanks, Ric
1. '80 batwing
2. '78 pumpkin, control arms, wheel assemblies, struts, half shafts, shocks and u-joints.
The '78 would be stored, waiting for the solid axle.
Would this appproach work? Any comments or suggestions would be greatly appreciated.
Thanks, Ric
Melting Slicks
Joined: Jun 2003
Posts: 2,802
Likes: 241
From: Niles, MI