New 3.55 SG install gone bad?

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Ded Sirius

Ded Sirius

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Ok, I am still having the horrible binding and shuddering in my new rearend whenever I turn, going either backward or forward. Worse going backward and worse turning right. It's seemingly just like the SG unit is not slipping all the way. Drives like my truck in 4 low on pavement. Inside tire slippage. Absolutely no problems when going straight F or R. Should I pull it out and reinstall? Added the LSD friction modifier. Car sat filled for a week. I have taken it out 2 times for about 25-30 miles so far in varying types of roads and a little highway. Did I miss something in installation? Help please.
 
You need to get in a parking lot and do some figure 8s. That will break the clutches in and get the lube mixed up good with the friction modifier.
 
The Mopar Performance / Mancini SG rebuild kits are REALLY tight. My big heavy SFGT with some decent rubber experiences the same thing with the 3.91 diff I built for the track. It is a bit annoying. Half tempted to redo it with the looser clutchs that Dr..Diff sells when I put the original 3.23 pumpkin back in the car. Other half tells me it'll eventually loosen up.

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67valiant 100 said:
The Mopar Performance / Mancini SG rebuild kits are REALLY tight. My big heavy SFGT with some decent rubber experiences the same thing with the 3.91 diff I built for the track. It is a bit annoying. Half tempted to redo it with the looser clutchs that Dr..Diff sells when I put the original 3.23 pumpkin back in the car. Other half tells me it'll eventually loosen up.

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That Sport Fury GT is awesome!

Love to see more pics of that incredibly rare hotrod!!
 
Ded Sirius said:
Ok, I am still having the horrible binding and shuddering in my new rearend whenever I turn, going either backward or forward. Worse going backward and worse turning right. It's seemingly just like the SG unit is not slipping all the way. Drives like my truck in 4 low on pavement. Inside tire slippage. Absolutely no problems when going straight F or R. Should I pull it out and reinstall? Added the LSD friction modifier. Car sat filled for a week. I have taken it out 2 times for about 25-30 miles so far in varying types of roads and a little highway. Did I miss something in installation? Help please.
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What diff lock did you use? I have a Dr Diff trac lock style and sticky tires and it is the same. Any Detroit locker style will do that. We have a full Detroit Locker in my sons car. Does the same thing. Very heavy spring and dog tooth gears versus clutches.
 
71GSSDemon said:
What diff lock did you use? I have a Dr Diff trac lock style and sticky tires and it is the same. Any Detroit locker style will do that. We have a full Detroit Locker in my sons car. Does the same thing. Very heavy spring and dog tooth gears versus clutches.
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Agreed. I had a Detroit Locker in a 9" in one of my old '69 Mustangs back in the day, and they took some getting used to.
 
halifaxhops said:
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But the tag says it has both....


Anyway, back to OP. Based on the fact they mention both SG and Posi, I would question which unit they put in it. My Dr Diff differential and Detroit lockers do as mentioned, may not be anything wrong with it. May just take some time to get used it. Also, I found on a really light car, it can act like a spool and not even unlock but occasionally.
 

Took it out yesterday for figure 8s and light cruising. Definitely getting quieter. Still noticeable in some turns. Will drive it a bit livlier today before I put it up. Thanks for all the help.
 
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