Gear ratio thoughts?

[superhondaz50]

Ok, looking for thoughts on gear ratios for my tow truck. Truck is a 69 C10 350/T400, 12 bolt rear with 33" tires. Load is a jetski trailer approximately 2,000lbs, plus maybe 400-500 in the bed. Will be towing mostly on CA freeways into AZ. Speed limit never exceeds 55mph. I will occasionally use the truck to commute to work so it'll also need to be able to hit at least 75mph. I have a brand new 3.42 set I was gonna throw in, but I'm thinking it might be insufficient. Any thoughts? Thanks

[harpo231]

3:73 And she might whine a little at 75 3:42 might struggle if uphill steep .

[demian5]

My 3:07 and 350/350 with 31" is awesome!

[rsavage]

If this attaches, here is a chart that can help you determine gear set:

https://www.4wheelparts.com/off-road...QaAjnoEALw_wcB

[68Gold/white]

What gear is in it now??? The 3.42 will work fine. My experiences with vehicles has been a learning deal. I will never lean towards the MPG side, always the power and drive-ability is only way to go. These heavy vehicles can be made to get fair MPG, but it's usually expensive and not for the squeeze.

If it has 3.73 in it, I'd leave it alone.......

[superhondaz50]

Currently has a 3.08, ran 31" tires with that. Doing a ground up, it now has 33's on it and am at the rear end rethinking my 3.42's haha, just thinking I may have wanted 3.73's but am not sure

[davepl]

Best option: 4L80E + 4.10s

The steeper first makes it more like a 5.14 and the overdrive makes the final drive about a 2.90:1. Eat your cake and have it too!

[outfield]

Leaving the 3.08 gears, you can just down shift and run in 2nd on the steep hills. I ran 3.08 gears in a '78 4x4 for years with 33's and it was fine for all around daily driving and hauling.

[superhondaz50]

Originally Posted by davepl

Best option: 4L80E + 4.10s

The steeper first makes it more like a 5.14 and the overdrive makes the final drive about a 2.90:1. Eat your cake and have it too!

Thought about that, but I already have a Jegs TH400 sitting in a crate in my garage

[superhondaz50]

Originally Posted by outfield

Leaving the 3.08 gears, you can just down shift and run in 2nd on the steep hills. I ran 3.08 gears in a '78 4x4 for years with 33's and it was fine for all around daily driving and hauling.

I suppose I can downshift with the 3.42 also haha

[Alex V.]

Another vote for 3.73's. My '85 has 32's and 4.10's behind a turbo 400 - it's right in the sweet spot at 55-60, but anything over 70 has it spinning pretty good. In your case, 1" more tire and the next faster gear should keep 75 comfortable enough and retain as much towing prowess as possible.

[jocko]

If funds permit, o/d trans is the ticket - but in your case, with the higher gear, you'd really need a lower rear if you had an o/d trans or your rpms would be too low for highway cruising. Agree with Dave, o/d with a 3.73 with stock dia tires, 4.10 with anything much bigger than stock dia. Look at it this way - GM swore by O/D+3.73 combo for years in 1/2 ton trucks. Having said all that - the combo platter IS expensive, no matter how you chew it. So, since O/D only with your current setup isn't really an option - if funds are limited, I'd go with 3.73 as you have a slightly taller than average C10 tire there. Here's a chart to help explain some of the #'s. 3.42 will work fine, but your biggest sacrifice with a TH400/3.42 combo is 1st gear torque multiplication. Compare that combo's final drive numbers to a 700R4 with 3.73 or 4.10 for example. If you're just gonna cruise around and aren't worried about how cool a burnout you can do, 3.42 will be just fine. If you're gonna ever haul or pull anything, I'd go 3.73 minimum.

[superhondaz50]

Good info in that post above. Not really on a budget, just sold my Dodge ram and spent about $10k in parts for my c10, still have cash is reserve. So looks like 3.73 is ideal, but since I have 3.42's it should work ok. Don't ever plan on burning out lol just need to get my jetskis across 250 miles of flat 120* heated desert, the trailer total is only 2k lbs. Maybe I'll sell my 3.42 set cheap and get a 3.73 set...

[Mike C]

Originally Posted by davepl

Best option: 4L80E + 4.10s

The steeper first makes it more like a 5.14 and the overdrive makes the final drive about a 2.90:1. Eat your cake and have it too!

4L80 has same 2.48 first gear as the TH400

[Alex V.]

Originally Posted by Mike C

4L80 has same 2.48 first gear as the TH400

Yup - 4L80 is a TH400 with a .75 OD. The 700r4/4L60 is the one with 3-something first and .69? OD.

[jocko]

3.06/0.7

[superhondaz50]

Anyone wanna trade a 3.73 thick gearset for a 3.42?

[71meangreenc10]

Open Carrier or Posi?

Smitty

[superhondaz50]

Open, I have a Richmond 12BT342, new in the box. Would really like to trade it for the 12BT373T.

[Don Quixote]

With that setup, I think you'll be just fine with the 3.42. That will put you right about where you said you wanted to be.

[TBohne]

Superhonda I sent you a text