78 Rear Leaf Spring Problem
Le Mans Master
Joined: Jun 2019
Posts: 5,472
Likes: 2,180
From: Loveland
When you talk about removing one leaf from the spring,,,,, are you doing this to adjust the ride height? The ride height should be adjusted by the length of the bolt on the ends of the spring.
Just to reiterate, make SURE the two big forward differential bolts are not to long. If you change the spring and it is smaller, you will crack the diff when you tighten them down. Only tighten the 4 bolts with full weight on the rear.
When the rear ride height is correct, the two axle shafts will be perfectly horizontal with the full weight on the car.
Just to reiterate, make SURE the two big forward differential bolts are not to long. If you change the spring and it is smaller, you will crack the diff when you tighten them down. Only tighten the 4 bolts with full weight on the rear.
When the rear ride height is correct, the two axle shafts will be perfectly horizontal with the full weight on the car.
Last edited by kodpkd; Mar 3, 2023 at 02:19 PM.
Le Mans Master
Joined: Jun 2019
Posts: 7,653
Likes: 2,468
From: Indiana
Le Mans Master
Joined: Jun 2019
Posts: 7,653
Likes: 2,468
From: Indiana
the eaton spring comes with a thick plate.. it makes the spring taller than original. Remove the plate then the height is the same as original. Eaton confirmed ok to remove. It is not a leaf..note the original plate is very thin and the original leafs are thicker (6) than the eaton 7.
i suppose you can leave it..but make sure bolts are in far enough..I want to be sure bolts were as original depth. No more to possibly crack case..no less to possibly sacrifice holdng.
i suppose you can leave it..but make sure bolts are in far enough..I want to be sure bolts were as original depth. No more to possibly crack case..no less to possibly sacrifice holdng.
Le Mans Master
Joined: Jun 2019
Posts: 5,472
Likes: 2,180
From: Loveland
I understand. Probably wont hurt anything. My guess is they put the top plate on the spring for stability. This will match the differential mounting better than the curved spring. Longer front mounting grade 8 bolts would also solve the issue.
I would like to know how much the original gray spring was sagging?
I would like to know how much the original gray spring was sagging?
Le Mans Master
Joined: Jun 2019
Posts: 7,653
Likes: 2,468
From: Indiana
I understand. Probably wont hurt anything. My guess is they put the top plate on the spring for stability. This will match the differential mounting better than the curved spring. Longer front mounting grade 8 bolts would also solve the issue.
I would like to know how much the original gray spring was sagging?
I would like to know how much the original gray spring was sagging?
op’s spring is toast..
Thread Starter
Melting Slicks
Joined: Aug 2000
Posts: 2,388
Likes: 42
From: Murrysville PA
Originally Posted by interpon;[url=tel:1606344594
1606344594[/url]]the eaton spring comes with a thick plate.. it makes the spring taller than original. Remove the plate then the height is the same as original. Eaton confirmed ok to remove. It is not a leaf..note the original plate is very thin and the original leafs are thicker (6) than the eaton 7.
i suppose you can leave it..but make sure bolts are in far enough..I want to be sure bolts were as original depth. No more to possibly crack case..no less to possibly sacrifice holdng.
i suppose you can leave it..but make sure bolts are in far enough..I want to be sure bolts were as original depth. No more to possibly crack case..no less to possibly sacrifice holdng.
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Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
i was gonna say the same. everybody else is trying to get their cars lower. you can shorten up on the rear spring bolts after replacing the squished end bushings to get it as high as you want.
Le Mans Master
Joined: Jun 2019
Posts: 5,472
Likes: 2,180
From: Loveland
Wow,,,, 89vette. This is the first time I have ever seen a spring that sagged out. You are correct, that end bolt has been shortened up more than enough. You can even tell by the upwards angle of the end of the spring. I hate to say it but with the rust, there is probably more restoration you could do on the suspension. Thanks for the picture.
Pro
Joined: Mar 2022
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Thread Starter
Melting Slicks
Joined: Aug 2000
Posts: 2,388
Likes: 42
From: Murrysville PA
Yes it’s bad. This is my fathers car that he bought new in 78. It has 30,000 miles on it and he’s started driving it again recently. I’m a car guy and he’s not. He thinks since it only has 30,000 miles, it can’t be worn out but he has no sense of time. I have a lot of performance cars new and old and they are all in top condition. I drove it last week as he said there is something banging in the back and he sure is right. There is a horrible sound coming from the rear under acceleration that sounds like the driveshaft is hitting something every revolution. It needs to be put up on a lift and diagnosed. I told him not to drive it but he doesn’t listen.
I like projects like this but this car is a slippery slope. It’s going to turn into a much bigger project. I think the whole rear suspension is going to need rebuilt. Oh yea and the carb is screwed up and it runs pig rich. The exhaust burns your eyes.
He’s going to be 80 this year. He has his own jet and flies it and keeps it in perfect condition but this car just isn’t his passion. If it had wings it would be a different story!
I like projects like this but this car is a slippery slope. It’s going to turn into a much bigger project. I think the whole rear suspension is going to need rebuilt. Oh yea and the carb is screwed up and it runs pig rich. The exhaust burns your eyes.
He’s going to be 80 this year. He has his own jet and flies it and keeps it in perfect condition but this car just isn’t his passion. If it had wings it would be a different story!
Intermediate
Joined: Feb 2006
Posts: 37
Likes: 0
around 2005 I changed the rear spring on my 78SA from stock (9 leaf) to a F-41 (7 leaf) spring and I used longer bolts and all new rubber bushings. The car rides very hard. If I had to do it again I would look into a softer fiberglass spring.
Le Mans Master
Joined: Jun 2019
Posts: 7,653
Likes: 2,468
From: Indiana
the eaton gymkhana spring is not hard at all and should Not use longer bolts. If you need longer bolts the spring is not correct.
