GM 4108 Reverse Gearing

[richard5933]

Anyone know what kind of gear ratio is used in the reverse gear of the Spicer 4-speed I've got in this thing? Seems to me that it doesn't like going uphill at all in reverse, requiring a bit of throttle to avoid stalling.

Can easily do a no-throttle start up the same grade in 1st, which got me wondering about the reverse ratio.

[TomC]

Stands to reason that it must be pretty close to 2nd gear since you have to pull the transmission into second to get reverse.
On my V730 Allison, reverse is somewhere between 1st and 2nd gearing. I once tried to see how fast I could go in reverse in a really big empty parking lot (since my speedo works in reverse too). I got up to 40mph and chickened out. Wish my trans had the same reverse as the HT740. Good Luck, TomC

[chessie4905]

Richard, you have the factory service manual. Look it up in rear of transmission section. Or, put in the automatic. Reverse in GMs, although very durable, sucks when trying to back up a grade. Even worse in the 4104's. Same trans used in other manual 4 speeds in mci's of that period. The one thing I disliked about the 4104.

[DoubleEagle]

That agrees with what Fast Fred said (on BNO) years ago: "Reverse on most GM is somewhere between 1st and 2nd , so backing up a steep grade may tax your clutch mightily." There must be several versions of the Spicer four speed over the years. In my 1975 Eagle, the reverse seemed to be very close to first, and I have used it to back up hills to get into difficult to reach camping spots. I now prefer the Allison's forward or backward.

[chessie4905]

A family friend, Sam Crawford, used the gears from an ACF Brill to improve the starting and backing up ability of his 4104. Since I first had a Brill, it did start out and back up easier, however the penalty of that gear pack resulted a lower 3rd ratio at the governed speed of 2200 rpms to 40 mph. (4:11) rearend. Imagine having to wait for your coach slow on a grade to 40 mph, before down shifting.

[richard5933]

Thanks for the replies. This confirms what I hoped - it's not my driving that's the problem, just that the thing doesn't do well going in reverse uphill. Good thing to remember for future parking.