Spring-to-differential bolt sizes?
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
Spring-to-differential bolt sizes?
Well, changing the rear shocks has turned into more of a project than anticipated (what's new).
One of the shock mounts was stripped, so I ordered two new ones. After discovering some loose bolts on one of the half shafts, I started checking everything else and I discovered that the spring-to-diff bolts were loose and, as far as I can tell, not grade 8.
So, I was just going to go down to the hardware store and get some new ones, but I want to make sure I get the right size(s).
I dont think the previous owner had the correct ones in there because he had two different sizes in the rear holes.
Could someone tell me what size they are supposed to be on a 1969? I know they are 7/16-14, but I want to get the correct length, esp on the front of the diff.
Also, what should these be torqued to?
thanks in advance
One of the shock mounts was stripped, so I ordered two new ones. After discovering some loose bolts on one of the half shafts, I started checking everything else and I discovered that the spring-to-diff bolts were loose and, as far as I can tell, not grade 8.
So, I was just going to go down to the hardware store and get some new ones, but I want to make sure I get the right size(s).
I dont think the previous owner had the correct ones in there because he had two different sizes in the rear holes.
Could someone tell me what size they are supposed to be on a 1969? I know they are 7/16-14, but I want to get the correct length, esp on the front of the diff.
Also, what should these be torqued to?
thanks in advance
Racer
Joined: Oct 2005
Posts: 449
Likes: 0
From: Boulder CO
I just replaced the spring on my '72 last weekend. I still have the old bolts for the plate holding the spring to the diff, so I'll measure them tonight and post the length for you. Unless someone else beats me to the punch!
I also seem to recall the Chevy Shop Manual indicating 70# of torque for these guys.
I also seem to recall the Chevy Shop Manual indicating 70# of torque for these guys.
Le Mans Master
Joined: Aug 2000
Posts: 6,362
Likes: 7
From: Brazos TX
Cruise-In IV Veteran
Cruise-In V Veteran
Scott, there are two different rear covers. One for most cars (and probably yours) '63-'77 with 2.25" wide rear spring uses 9/16-12 x 3.5" bolts and the other for '78-'79which uses 7/16" bolts and a 2.5" spring. I don't know the lenght on those but I can get it if you really need it.
Le Mans Master
Joined: Aug 2000
Posts: 6,362
Likes: 7
From: Brazos TX
Cruise-In IV Veteran
Cruise-In V Veteran
It must have been changed at some time. I'll crawl under the car and see what I can get for you. Is it cold enough for you today! It's 35 degrees out here and I have to drive out near Abilene this afternoon. I'm hoping we don't get any freezing rain or ice on the bridges.
Le Mans Master
Joined: Aug 2000
Posts: 6,362
Likes: 7
From: Brazos TX
Cruise-In IV Veteran
Cruise-In V Veteran
Ok, they are 3.25" long (shank and threads but not the head). Is that 70 ft/lb torque for the 9/16" bolts? I think 70 is a bit high for a 7/16 bolt. Maybe 55 or 60 would be better.
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
Burning Brakes
Joined: Aug 2004
Posts: 971
Likes: 7
From: roanoke va
There is also diffrent lengths of bolts depending on how many spring leafs you have. I think zip list the bolt's lenth and size for 7 or 9 leafs in their book. Make sure you get the right length because you can bottom the bolt out and bust the rear cover.
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
Burners- Thanks a bunch for checking that out for me. I hope you dont hit any of the slick stuff either! It's like 39 here.
wills670- D'oh! good call. Mine has the fiberglass monospring
Guess I'm just going to have to run different lengths in there (carefully) and see what fits.
tracdogg2- I'm not concerned with keeping it original (not much of it is anyway), but is there any advantage to the 2.25 cover?
alanbl- thanks for the offer!
thanks all for the help and responses
wills670- D'oh! good call. Mine has the fiberglass monospring
Guess I'm just going to have to run different lengths in there (carefully) and see what fits.
tracdogg2- I'm not concerned with keeping it original (not much of it is anyway), but is there any advantage to the 2.25 cover?
alanbl- thanks for the offer!
thanks all for the help and responses
Racer
Joined: Oct 2005
Posts: 449
Likes: 0
From: Boulder CO
First the weather report since all you Texans are reporting the cold 35 & 39 degree temps. Up here in one of the north counties of Texas (Colorado) the temp is -10 at my house. That's minus 10.
The bolt is 3 1/2" long and I had a 9 leaf spring, each leaf 2 1/4" wide. Confirmed that the shop manual calls for 70# torque while the assembly manual indicates 60-80#. Here it is:
The bolt is 3 1/2" long and I had a 9 leaf spring, each leaf 2 1/4" wide. Confirmed that the shop manual calls for 70# torque while the assembly manual indicates 60-80#. Here it is:
Last edited by alanbl; Feb 17, 2006 at 08:44 PM.
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
Originally Posted by alanbl
First the weather report since all you Texans are reporting the cold 35 & 39 degree temps. Up here in one of the north counties of Texas (Colorado) the temp is -10 at my house. That's minus 10.
Thanks again for checking that.
Tech Contributor
Joined: Aug 1999
Posts: 15,175
Likes: 3,986
From: Connecticut, USA
1 quick note if using a new HD cover. They are very good and I use them in my jobs but the castings are off a little. I've had to fit everyone to the cross member because they didn't jsut bolt in.
Also the center to center on the 4 bolts is tighter so you may have to grind reliefs in the spring for bolt clearance or you'll roll the threads for sure.
Also the center to center on the 4 bolts is tighter so you may have to grind reliefs in the spring for bolt clearance or you'll roll the threads for sure.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Originally Posted by Shrike
Weird!
Mine definitely has the later model rear end because it has 7/16 bolts.
I mostly need the length on the two front bolts so that I don't bust anything.
Mine definitely has the later model rear end because it has 7/16 bolts.
I mostly need the length on the two front bolts so that I don't bust anything.
Or.... somebody installed a spring kit that included thread inserts .... common in aftermarket spring setups.
These kits reduce the thread size from the larger to the smaller. I've had to remove these on occasion.
