TXTad

Howdy!

I really like my new 2006 and the transition to auto hasn't been too bad. Since the top ratio of the 48RE is pretty similar to the NV5600 I had before, there's not much difference there and the overly large gap between 3rd and 4th is the same as 5 to 6 in the NV5600. To address the 3rd to 4th jump, I've considered a Gear Vendors over drive unit, but it's really a bit too much over drive. It's 22%, which moves 3+ closer to 4 than 3. On the 48RE, 3rd is 1.000 and 4th is .69. With a GV unit, 3+ would be .78, making the drop to 4th only 12%. A 17% overdrive would split the difference a lot better. Even worse is 4+ at .54. With the 3.73 rear end, 4+ is only 1300 RPM at 60 MPH, and even 80 MPH is only a hair over 1700 RPM.

The good news is that the 68RFE looks like it has very good ratios with the dual over drive and a slightly higher 6th and the 48RE's 4th, but I just got my 2006 and I don't want my wife to stop loving me like she would if I said I need a 2007. Besides, no matter how much testing they've done, I'd rather not buy a first year transmission and engine combo.

So, back to the 48RE. Does anyone have a GV unit with the 3.73 rear end? I'm thinking that the GV unit might make sense if I was to also change the differentials to 4.10 gears. (I wonder what that will cost.) The spacing is still odd, but at least 4+ is a little more usable with 70 being 1650 RPM.

I wonder if a 68RFE is a realistic swap into a 2006 some day?

Tad

TonyB

There's a few members that have them. I seem to remember they have a 4.11 diff, though.

I've had similar thoughts...

3.20 @ 55 = 1283 rpm
3.20 @ 75 = 1749 rpm
3.55 @ 55 = 1423 rpm
3.55 @ 75 = 1941 rpm
3.73 @ 55 = 1495 rpm
3.73 @ 75 = 2039 rpm
4.11 @ 55 = 1648 rpm
4.11 @ 75 = 2247 rpm

I showed the 3.20 gear as it's an equivalent to 4.11 w/ 22% OD. That seems like a sweet spot, to me at least. But, I'd have to change gears to 4.11 and install the GV OD.

I've had thoughts of just changing the gears to 3.55, but can't seem to justify it for just a 100rpm drop. Nor can I gamble on saving money with the GV OD at ~$3k!

Tony

TXTad

3.73 in the 3rd gen trucks is about the same as 3.55 was in the 2nd gen trucks, so I think 3.55 in a new truck would be too much gear at low speeds. You'd lose a lot of your pulling ability. The nice thing about swapping to a 4.10 and going with the GVOD would be that you'd actually get a better low end AND top end.

Everyone that's ever talked about their GV unit has liked it, so I don't think the $3K for that is much of an experiment, just an expense. I need to find out what a gear swap to 4.1 front and back would cost.

Tad

BigBlue

Figure roughly $600 in gears (have to do front and rear axle) and $600 for labor.

TXTad

According to the Sterling Bullet website, their trucks are available with gear ratios of 4.10, 4.44 and 4.88. 4.44's with the GVOD will still lower 70MPH RPMs to just under 1800. That might make a sweet pulling truck.

Tad

CrazyCooter

Try to finding 4.44 gears for the front.

TXTad

Is that a problem with these axles being new, and therefore not having a lot of parts available yet, or is that something that is likely to never exist? Well, it must exist, the Sterling Bullet Specification page lists those ratios as being available on the 2wd and 4wd models.

Tad