Rearend differences

[royce71]

I have had a '79 Spider for over a year now and am finally getting around to restoring it. I am planing on putting "before" pictures on the forum soon. I have found a source for used parts here locally and he gave me a rearend from an '81 automatic just for taking his rust free '81 body from him for $50. I was wondering if it would help or hurt my performance because I know that the ratios are different. Any help would be appreciated.

[So Cal Mark]

the auto diff has a 3.58 ratio compared to 3.9 on your manual diff. It will affect acceleration quite abit, but lower your cruising rpm. It's not a good trade-off in my opinion

[royce71]

Thank you. I was only considering it because the auto has only 24000 miles on it compared to 87000 on the one in the car.