i had my heart set on a 2200-2400 or a 2400-2600 stall convertor and a set of 3.73 gears. however, using the 700r4, my revs at 70 mph would be about 2400. from what i remember, its not good to have the revs close to the stall, especially at highway speeds. i was looking into 3.90 gears, but my revs would be 2400 at 70 mph with 255/60/15 tires. im going to go with a wider tire, im hoping i can get a 275/45 or 295/45, which would bring the revs to 2600 at 70 mph. if i go to 4.10 gears, the revs bump up to 2700. i wanted to keep the possiblity of running up to 150 mph, but the 4.10's are too short for it to really make it.

also, im not 100% sure if the 86 700r4 uses a lockup converter or not. i never felt the old convertor lock the way it did on my honda and blazer. i think it is.

should i go with the shorter gears and higher stall, or lower stall and higher gears? the car is going to be a weekend cruiser/drag race/road course/highway road trip. its an 86 with a 350 crate engine around 400 hp.

 

Yes, it is a lock up converter. When the converter is locked at cruising speed, the stall of the converter does not matter.

 

^ Just beat me to it, all 700R4's use a lockup converter! And for the sake of 4th gear lubrication, you want to use a lockup. Also, the 1988 and up 700R4's are more durable. If you're not getting your 86 trans built up, 400+ h.p. is going to smoke it.

 

I thought they went from a 28 to a 31 spline input shaft in 1986 (IIRC) and that was the only real difference.

 

There are some internal differences as well. The later model had better lubrication to the low-reverse planetary gearset, an improved oil pump, and a "secondary" valve body (an accumulator that gave better lubrication to low gear). I have read sources that say 1987 and newer and I have also seen 1988 and newer as being the updated version. So I don't know if it was at an exact year, or somewhere between the two.

 

i do know that the later models are stonger, however mine doesnt even have 10k on it since it was fully rebuilt. i dont plan on leaving it stock. it already has a shift improver kit, which i plan on upgrading to one with even firmer shifts. the governor is being recalibrated to up the shift points, an additional cooler is being added. there are a few other things i have written down that are going to be upgraded as well, i just cant remember them all. i just needed some assistance with chosing gears and making sure that it was a lockup.

now my question is 3.73's or 3.90's?

 

3.73's if you plan on driving it on the interstate. I have 3.42's and hold about 2500 at 75mph.

Now that you mention it, I do remember those changes now. When I had my 83 700R4 built, he corrected all of those differences, and now it's good for 650 hp

 

If you're looking for a wider 15" tire, you want to be looking in the 50 series. There aren't 45 series tires in the 15".
I have Firehawk 295/50/15's on mine. Although their specs show they have a 26.7" diameter, in real life they're closer to a little under 26". Mine measure 25.5" from the ground to the top, factoring in normal tire squat. You're going to have to do some measuring to see if you have that much fenderwell depth to cram in a tire that size.
With those diameter tires, and 3.73 gears, your engine will be spinning 2361 rpm's at 70 mph. With 4.10 gears, it'll be at 2596 rpm's.
Mine doesn't have O/D, so with 4.10's mine is winding at 3708 rpm's at 70 mph. Your numbers don't look so bad from where I'm standing. But you might be happier with the 3.73's if you do combination highway/city driving. If your car rarely sees the highway, you'll have more fun with the 4.10's.

 

there isnt much intersate around my area other than when i want to avoid "town" but i do plan on going to car shows and spending some 4 hour trips on the highway. i think i might go with the 3.91's when i order the moser 12 bolt.

and what do they offer between 255 and 295? im going to have my rims widened to 9 inches, idk if there is a 275/50? if its needed, i will just use a spacer, but im pretty sure i can keep the tire under the fender

 

I like your thread.

___________
Lilian
fast money