Gear Ratios for A GM 4107

[luvrbus]

What is the highest ratio GM had and are the pumpkins the same as other model of the buffalo .I have to pull a V730 to replace the engine rear main seal that filling the 730 with engine oil,and want to change the ratio since it's a 8v71 turbo and top speed is 63 mph at 2250 rpm   

[Bill Gerrie]

A friend of mine had a 4107 with a 4:10 rear in it. His top speed was 71 mph.

[TomC]

4.1 with 11R-24.5 rubber (476rpm) and the V730 with .88 overdrive will give a final drive ratio of 3.608. This will give a 60mph cruise at 1717, 70mph at 2003, 80mph at 2289. Startability is not that good. But with a 4107 that probably weighs around 28,000lbs and an 8V-71T putting out around 1,000lb/ft torque, he should have a startability of 25%. Reverse is worse since it is like a gear between 1st and 2nd

I have 4.56 gears that give me 60mph at 1950. In a big parking lot that was empty, I tried reverse. Since my speedo works both ways. I got up to 40mph in reverse and chickened out. Good Luck, TomC

[Fred Mc]

Not sure if this helps or even has any bearing on the situation but with a stock engine/tranny in a 4106 I could get well over 80mph. don't have a tach so don't know rpm.

[chessie4905]

they were only available with two ratios. 4:27 and 4:11. about 4 to 5 mph difference in top governed speed.  4106,7, and 8 had the 4:11's standard. 4903 and 5 had 4:27 standard, with the 4:11's as an option.Why they didnt offer 3:90 or 3:70, no one knows. Maybe their tests when designed new showed the engines were taxed when loaded with a numerically lower ratio, especially since low gear was actually second, and when in high gear, actually, not technically in overdrive.
I also dont know why Tom doesnt go to 4:27's to gain 6 or 7 mph higher cruising speed.

[Runcutter]

Clifford, the only thing I can find in my 4107 maintenance manual is that standard was 4 1/8 to 1.  Maintenance manual doesn't show any options.  I can't find any reference to the differential in the parts book I have.

Probably doesn't help, but at least it's one data point.

Arthur

[chessie4905]

manual too old, you missed it, or didnt mention in 4107 because wasnt needed or too early before it was mentioned. Its in the 4108, 4905 manuals.

[olebusman]

  4&1/8 is it, BUT while the tranny is out make it into a teal overdrive unit then you won't care which rear gear you have. My top speed is way faster than the tires are rated for and I love the overdrive. I can't believe that others haven't done it. Mine is a 4106 with a 6V92 with a 4&1/8. I think a 4&3/8 would work very good.

[chessie4905]

Lack of parts for it. The vs series have been obsolete for years. Great thing though.

[Bill Gerrie]

John olebusman
You and I are the only ones with the O/D unit other then the original one. Parts are just too hard to get now. I love it. I can cruise at 65 mph at about 1700 rpm. Come to a hill and just drop it out of O/D. I also have a 6V92TA with it. Been using it since 2006.

[chessie4905]

I need the vs2-6 planetary gear set and clutches yet. Have the rest.