4.10 or 4.56 gears for 33's.

[Destructo]

I need to re-gear my 85 4x4 so I can actually use OD and have good towing power in 3rd gear. Specs of the engine are in my sig. I have used the gear calculators and all that but don't know if they would be accurate for an automatic transmission with the torque converter locked up, I have manual lock-up for 3rd gear and automatic for 4th gear, will the clutches slip or when the torque converter is locked up will it just be like a manual?

I need good power and torque for towing but also need to find a compromise between daily driving and towing power, its going to be towing my Suzuki Samurai on a trailer and needs to cruise down the highway in 3rd gear.

[1FaastC10]

4.10s all the way

[SanitysBane]

i thunk wit a 33 might need lower(high numerically) than that, i once know of a website that told u what was the ideal rear end ratio but i forgot it long ago, sorry

[Destructo]

Thats what I was thinking, got 3.42s right now, can't use OD at all unless are flat ground and it works but gas mileage wouldn't be any better because I have to give it just as much or more throttle than 3rd locked up right now.

I'm trying to find some guys that have personal experience with a 700r4 and 33" tires, I don't trust the calculators that much, I have a fairly small cam so 2k rpm cruise in OD should ok but might want a little more for better mileage.

[1FaastC10]

4.10s are about optimum for 35s, so i dont see why you would need or want any lower you'd just be killing any chance of "economy" for a little extra unneeded towing power. unless of course, you're pulling large equipment or something, at which point you need to ditch the idea of a 1/2 ton SWB anyways.

[Destructo]

Remember I have a 700r4 with a 4th gear of .7 I have heard 4.10s for 33's and 4.56 for 35s, but I don't know what actual rpm I would see on the highway in 4th and 3rd. I want atleast 2k rpm in 4th gear.

Gear calculators show that in OD and 4.56 gears I will turn about 2100 rpm at 65mph and about 3k rpm in 3rd gear.

[1FaastC10]

you're not towing in OD, or you shouldnt be at least. you want to tow in 3rd gear. at which point your final drive becomes the same as any other non-OD trans. 4.10s are where you want to be.

at 65 mph, and assuming your tires are actually 33" tall, with a 4.10 in OD, you should be pulling around 1900. once you calculate for converter slippage, you're right around your 2000 goal. for towing, you're going to want to keep it in D, and not OD. you'll be turning around 2700 in the same speed range.

[Destructo]

No slippage in my torque converter with a lockup, even in 3rd I have the converter locked. I figured 3k rpm would be best for towing and 2k or more for cruising in OD. I know not to tow in OD unless I want to fry my 700r4 that I just rebuild 8k miles back.

[85 K5]

Only for comparison, I'm running 3.73's and 33's. (700r4) 70 mph is 1900 - 2000 rpm. 65 mph towing in 3rd is 2700-2800 rpm. With an rv cam, qjet and eddie performer rpm it will maintain 70 uphill into the wind without downshifting. Sometimes wish I had gone with the 4.10's.

[Jonboy]

I had always heard 4.10's for 33's, and 4.56's for 35's also, but that was in a suburban, too. How do you use the truck? That would probably be the determining factor. IMO, just going to 3.73's from 3.42's wouldn't be enough to warrant the expense. I think Motive gear sells a 3.90 gear kit, which would be almost ideal.

[Destructo]

The truck is just a daily driver and I also use it to tow my off-road rig around. My off-road rig doesn't weigh much, less than 3k lbs its a suzuki Samurai.

[Grim Reaper]

4.10's and 35s is about 3k at 70 on a TH350. If I had a 700 I would have gone with 4.56.
I would say with towing that you might be happier with the 4.56 and the 700. It will take a lot of stress off the tranny.

http://www.ring-pinion.com/calculato...latorsind.html
Has a really nice gear calculator and you can figure out your RPM with both gears.

With OD your 65mph cruise is going to be 1929 (thats figuring a 32.5 inch tire...most tires are short of the listed size). 2829 in Drive. The 1929 is too low for towing in OD and you will fry it. It would be fine for towing in drive.
With 4.56 at 65 your turning 2145 in OD and 3146 in drive. Now you could run the OD on the flats with a trailer. Still want to be out of OD in the hills.

[Destructo]

The main reason I need to change gears right now is because I can't tow much weight without suffering on the hills, I can tow on flat ground in Drive just fine but once I get to the hills it can't keep up and I feel like I have a fairly stout motor but the gears are holding it back now and I would like to be able to use OD otherwise I would have just put a th350 in it haha.

4.56 doesn't seem to be a whole lot higher than 4.10 and would give me a little more towing power but I would still get good gas mileage in Overdrive, i'm really leaning towards 4.56 right now if all the gear calculators are accurate, just over 3k rpm towing isn't bad at all and just over 2k in OD is better for mileage I think that 1900.

I'm probably going to go nuts deciding which ones to get. Its a much easier decision for my samurai, 5.38s all the way! haha.

[Captkaos]

This is how I would figure it.....
Stock the truck came with 215/75/15's (27.6" tall) and 3.42 gears. RPMs at 65 in OD would be about 1894 rpm.
If you go up to 33" tall tires (actual it probably ~32.5) and 4.11 gears the RPMs at 65 in OD would be about 1930 rpm. This will put the truck back close to the same RPM as the factory had it. If you want more pulling power, you will have to move the gear ratio up numerically, or shorten the tire size. For example, 4.56 gears with 33" tall tires will just the rpms up to about 2150 @ 65mph, 31" tall tires with 4.10's will put it at about 2055rpms @ 65mph

[Captkaos]

Originally Posted by Destructo

I'm probably going to go nuts deciding which ones to get. Its a much easier decision for my samurai, 5.38s all the way! haha.

Do you go to Zuk Melt or any other Zuki gatherings? My brother has this Zuk now:
http://www.tmtoolman.com/Redzuk/redzuk0020.JPG
He used to have this one:
http://www.tmtoolman.com/images/mightymoe6.jpg

[Destructo]

Originally Posted by Captkaos

This is how I would figure it.....
Stock the truck came with 215/75/15's (27.6" tall) and 3.42 gears. RPMs at 65 in OD would be about 1894 rpm.
If you go up to 33" tall tires (actual it probably ~32.5) and 4.11 gears the RPMs at 65 in OD would be about 1930 rpm. This will put the truck back close to the same RPM as the factory had it. If you want more pulling power, you will have to move the gear ratio up numerically, or shorten the tire size. For example, 4.56 gears with 33" tall tires will just the rpms up to about 2150 @ 65mph, 31" tall tires with 4.10's will put it at about 2055rpms @ 65mph

My truck actually came from the factory with the 31" tire options and 4spd auto (700r4) and GQ1 gear option (turned out to be 3.08 gears) Even when I bought the truck overdrive was hardly usable and it was all stock except for a 350 instead of a 305. I swapped in some axle from a 79 blazer because I thought I had 2.73 gears or something and thought the 3.42s would work better but turns out right now the 3.42s and 33's are about the same as the 31s and 3.08s. I'm actually thinking about taking the lift off and putting it back down to stock because I don't really like my lifted truck anymore now that I have my off-road rig, it rides rough, harder for people to get into, requires more expensive tires and all that, plus I like the look of a stock 4x4 better than my lifted truck, I was just looking back through some old photos of right after I got it and realize it actually looks better as a all stock truck.

I just bought my zuke a little while back, just got done doing a SPOA lift on it. I haven't been to zukimelt or gonzookin but will be going to Zuwharrie this fall as its only a 1.5hr drive from me. Those are both nice zuks, heres a pic of what mine looks like right now, its pretty ugly but I plan on putting a grill in it, some new fenders and painting it one day.