# 67 rear end



## mjingle (May 11, 2010)

got a safety-trac 2.78 YC can i change ring and pinion to 3.23 ?


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## AZgoatguy (Oct 13, 2011)

The following info is from the Internet, and based on it the 3.23 is not an option for your 2.78 carrier - bummer! However, though not a performance ratio, your Safe-T-Track 2.78 is a desirable axle for those wanting to get better mpg for their highway driven Goat. There is an active thread on the subject of changing axle ratios for mpg right now on the Performance Years GTO Forum - check it out. I've got a '67 YB code 2.56 Safe-T-Track in a car right now and it work for me.

GTO Axle Ratio Identification:
Three different differential cases are used. 
1) 2.56 and 2.78 ratios;
2) 2.93, 3.08, and 3.23 rations; and 
3) 3.36, 3.55, 3.90 and 4.33 ratios.


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## AZgoatguy (Oct 13, 2011)

More from my earlier post- Regarding the 2.56 and 2.78 ratios, these ideally would be used with an automatic transmission as they would be very hard on a clutch for manual shifting. I wouldn't recommend any gear taller than a 3.08 with a manual trans car. And even the 3.08 can be tough on a clutch if you drive for performance. My 2.56 gear works fine for me behind a 389 with a TH-400 trans but then I don't care about off-the-line grunt, and I still have good pull at speed but it doesn't push you back in the seat real hard either. Mpg is 19-20 on the highway and around 15 in the city - feels good to me.


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