: 1984 Sedan Deville Rear End Ratio?? 3:42

02-08-06, 08:38 AM
I keep hearing talk of gears in the 2:28-3:08 range in this thread, but I had my diff cover off and found 3:42's in my car??? God knows the 4100 needs it to move.......Is this common? Trailer Tow Package? It has an Engine Oil Cooler also...

Night Wolf
02-08-06, 11:43 AM
Yes, you have 3.42. All HT4100 (RWD) have them, it is a 7.5" GM rear end.

the 2.28 are 1977-1979 RWD. They had the 425 big block, and had the power and torque to move the car around with the ultra high gearing, they used a more heavy duty rear end too (8-7/8")

02-08-06, 12:43 PM
High altitude HT4100's have 3.73's stock.

Unless you are racing, towing or are just total hell on the car (NOT breaking rubber though) the 7.5 is fine. If you put slicks on and took it to the track regularly then worry about it. The LS1 powered Z28/TA's had 7.625"s, which is a 7.5" with a slightly bigger ring gear, and those gears also fit in a 7.5" case with the appropriate differential. Those things hold up to a lot of abuse.