Transmission/Gear Combo

[NCBowtie]

In the coming year, I am looking to swap in an overdrive transmission and new rear gears.


I'm thinking about going with a 2004r and 4.11 gears. Does anyone have experience with this Combo? My tires are 29" and most of my driving will be in the 45-55 range (think rural back roads). I will occasionally get out on the highway but keep it at the speed limit of 65. Very rarely I may get it up to 70.

[javelinmania]

I can't tell you the good/bad of specific rations, but the attached chart will show your RPMs. Then you decide.

[Eddie H.]

I recently did a 7004R and 3.73 gear swap in a 71 GMC with 29 inch tires. It is a great combination. It's very happy cruising at 75-80 mph without even breathing hard. 4.11 gears would be a little different, but not much.

[lutronjim]

I am going to disk brakes up front in my 70 C10 with LC9 engine. I understand that I will have problems with my current rims hitting calipers so I am off to new rims. Like the looks of 2001 oem rims on pickups. Putting whole 'k' member with brakes from a 87. Thinking of using after market rotor on front to keep 6 lug all around.

I have a 4l65e tranny with 3:73 rear. Love torgue around town but it only stays in first 'bout 1 second unless you romp on it. Would be nice to have a little taller ratio for highway. OD ration is 0.0696-to-1 for fourth gear

Any suggestion of wheels that would solve both problems?

Thanks

[jocko]

NCBowtie - if you are going to change out BOTH, the best streetable combo for perf and mileage is normally a 2004R (or 700R4) with 3.73 rear. There's a reason the factory likes this combo also. What kind of truck - C or K /10 or 20? Depending on what you have now, you might very well be able to only change ONE parameter (trans or rear gears) and get the desired end result. An O/D trans, especially a 2004R (with the lowest rpm producing o/d ratio - but also my favorite trans) may not be the best choice if you're going to live between 45 and 60 mph cruising. RPM may get too low in 4th. What trans and rear end combo do you have now? Are you certain 29" tires are the final solution? (Taller might be a good idea). Let us know what you have now and might have some good suggestions.

Here's a 3.73 and 4.10 comparison with a 29" tire. Very similar to javelin's chartm (clearly a fellow Excel geek ) - produces same #'s. But the one for you to focus on is the rpm @ 65 mph. And 1st gear overall ratio. 700R4 has a steep 1st compared to 2004R, so you'd be shifting out of 1st quite quickly, and it will chirp your tires quite easily with 3.73, probably TOO easily with 4.10s. Anyway. Something to stew on.

[BCOWANWHEELS]

Real hard to beat th350 and 3:08 gears

[jocko]

That is a good combo for cruising - but it lacks oomph in 1st gear. If hauling or wanting to accel quickly in 1st, this is not a good combo. BUT, if one is gonna drive it as a cruiser and isn't doing burnouts, I agree, it is a great combo - and most of all, a very inexpensive one (especially if it's already in the truck).

Really would like to know op's current combo, I bet there is a less expensive way to get the desired end result without changing out both the trans and the rear.

[NCBowtie]

I do already have a 3.08 open differential in a TH350. It's kind of sluggish. I'm not opposed to changing tires but I really like the look of my 255/70/15's. Since I have a new daily driver, this is just a weekend truck for me now also. So fuel mileage is not too big of a concern, but I do want the best setup for my situation. It has a stock 350 crate engine motor in it currently.

Would the 2060 RPM in 4th gear be alright in a 200-4R as cruising RPM? With my stock cam, I'd bet that's right in my power/torque range.

[Mike C]

I think you are on the right track, but the 3.73 will give you a little more leg on the highway. With the 4.10, the top gear RPM will be about the same as the 3.08. My own choice is going to be 3.73 and the TH 200 4 R.