I went from 4.10 to 3.54 with I believe 285/75- 16 and a t19 it cruise nice on the highway, but I did notice that if on a slight grade taking off now that it doesn't like second gear takeoff. I do plan to eventually put a zf5 in.
I guess you are referring to your 83 in your Sig.?
My 86 is a T-19 with 3:55 Diff., and 235/85/16.
I always start in 1st gear, then go to 3rd on the flat. On a slight down grade might start in 2nd.
2nd seems to be a bit too high to start in.
Starting out on a up hill grade with a load, or car Trailer, get started in 1st with the 3:55, is a bit of a challenge. Have to play with the Clutch to get her rolling.
With your 285/75 the tire is a bit shorter than the 235/85, so starting in 2nd is probably easier to get rolling. But with the 75`s the engine will spin over a bit faster at speed.
Couple summers back was at PNP and saw a 97 Van sitting in line to be processed. Looked to have the grey steel rims. Asked the MGR. anyway I could get those as they just throw them in the steel scrap Dumpster.
They Fork lifted it up front to remove them, then noticed the Hub Caps. Asked if I could but Tires and all? $350 out the door. Figured a set of good rollers for my other truck sitting in the yard.
After looking at them were in good shape, plenty of tread and Coopers which I use.
I threw them on the rear of my 86, and noticed the engine running at a higher RPM. So now run them on the front.
They are 245/75/16.
Thee are weak points on the ZF you mention.
The T-19 is probably a tougher trans. The weak point I read about is the Aluminum Bell Housing developing a crack. I have seen a few pictures posted.
I do have a spare I got at PNP a few years ago.
(can`t have too many spare parts)
But nothing if totally bullet proof.
A T-19 and a GV would be a good combo for the OD, but still not give any low start gear.
Best is a T-19 and a 3 spd brownie.
HMMM... and I do have one of those.
I can see where Brian`s C-6 slip-a-matic and a GV might not give the total performance he is looking for.
Goat