Posted by Greg Coffin [172.68.34.97] on Friday, June 28, 2019 at 23:26:42 :
In Reply to: WC-62/63 4BT 5:83, 4.89, 4.30? posted by Scott [172.69.170.73] on Friday, June 28, 2019 at 19:49:40 :
Hey Scott, I'm thinking about the same thing, though I have a 318 in my 6x6. I have a little more rpm range than you do. I still have 5.83s in mine, and over the last few weeks I've felt the need for some longer legs. I'm running 36" tires, and I think 4.89s are going to be just about right for me. If you are running 37-40" tires, I think 4.30s will be a little tall, ever for a diesel. With 4.89s and 40" tires you will be going about 61 mph at 2500 rpm in 4th gear. With 4.30s you will be pushing 70 mph. That's too fast for me, but I don't know what you are hoping for.
I would not go with an overdrive if you are staying with 5.83s. I feel like it spins the transfer case and diff pinions too fast. In fact, I think that a 5 speed direct is a great transmission, especially for a diesel, since it give you a gear in the dead spot between 3rd and 4th gear.
I could go on and on about highway vs off road use, and transfer case low ranges, but I think that's enough for now. I'm curious to hear what others have to say.
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