4.88 vs 5.38 with 35s and locker ID

wolf1790

wolf1790

Member
Joined
Apr 27, 2019
Messages
64
Location
Florida
2000 Sport
4.0 I6
NV3550
35" tires

So I found out my gear ratio this weekend, 4.88

Now I'm contemplating switching to 5.38 gears but was curious how significant of a difference would I see in regards to rpm/mpg/overall performance.

I've read a lot that 5.38 is ideal, but at least 4.88 is better than stock. Is it 100% worth it to switch or is it a matter of preference? My engine doesn't struggle with the 4.88s that it has.

Also, I'd rather not have to start a separate post for this, so can anyone help ID this locker I have? Looks like a True Trac from googling.

20190531_105025.jpg
 
Grimmjeeper.com will tell you everything.

4.88 is the typical recommendation for your transmission pushing 35s.

I personally would not be opposed to 5.13. 5.38 might be a bit much, but not the end of the world.
 
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jjvw said:
Grimmjeeper.com will tell you everything.

4.88 is the typical recommendation for your transmission pushing 35s.

I personally would not be opposed to 5.13. 5.38 might be a bit much.
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Appreciate the response and the link to Grimm Jeeper, looks like that will give me a bit of reading. But that at least answers my primary concerns, which is that it probably isn't going to be worth it to pay for a regear any time soon unless I run out of other mods.
 
wolf1790 said:
Appreciate the response and the link to Grimm Jeeper, looks like that will give me a bit of reading. But that at least answers my primary concerns, which is that it probably isn't going to be worth it to pay for a regear any time soon unless I run out of other mods.
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When using the calculator, your tire size is the center on the hub from the ground x2. Not the sidewall or the horizontal diameter. Measuring the height of the axle tube works well. Where the tape touches the tube is the hub center.
 
Looks like a TT. 5.38 is the usual rec for the 4 spd auto trans, 4.88 with the manuals. 5.13 would be a slight change, maybe or maybe not all that noticeable. 5.38 would be a noticeable change.
 
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The 5.38 ratio is typically recommended for 35" tires when the transmission is the 4-speed automatic 42RLE. For your NV3550 I'd stick with 4.88. I ran 4.88 with 35" tires when I still had my 5-speed transmission and considered it optimal. I run 5.38 now but that's because I now have the 42RLE automatic.
 
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Jerry Bransford said:
The 5.38 ratio is typically recommended for 35" tires when the transmission is the 4-speed automatic 42RLE. For your NV3550 I'd stick with 4.88. I ran 4.88 with 35" tires when I still had my 5-speed transmission and considered it optimal. I run 5.38 now but that's because I now have the 42RLE automatic.
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Rob5589 said:
Looks like a TT. 5.38 is the usual rec for the 4 spd auto trans, 4.88 with the manuals. 5.13 would be a slight change, maybe or maybe not all that noticeable. 5.38 would be a noticeable change.
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Ok I think that's probably where my confusion started was with the different transmissions. Thank you.

For the TT, Jerry I know you used to run them and had mixed feelings (lockers were way down the line for me, so it's just a pleasant surprise), but do you recognize them from the picture? It's the only one I've seen that has that smooth surface all the way around.
 
wolf1790 said:
For the TT, Jerry I know you used to run them and had mixed feelings (lockers were way down the line for me, so it's just a pleasant surprise), but do you recognize them from the picture? It's the only one I've seen that has that smooth surface all the way around.
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I took a look when you first posted that photo but I didn't recognize it. Sorry.
 
wolf1790 said:
Ok I think that's probably where my confusion started was with the different transmissions. Thank you.

For the TT, Jerry I know you used to run them and had mixed feelings (lockers were way down the line for me, so it's just a pleasant surprise), but do you recognize them from the picture? It's the only one I've seen that has that smooth surface all the way around.
Click to expand...


Looks like my old truetrac from what I can tell. It's not a true locker but it's better than nothing. In my old rig I had 4.88s, a manual ax-15 trans, and a truetrac in a Ford 8.8 rear and truetrac in a 30hp front. Truetracs aren't the best especially in places where 1. Your going to actually lift a tire off the ground, and 2. When you'll be in situation #1 with a manual transmission.

The truetrac needs SOME resistance on both tires to operate, so applying the brake can help lock it up with a lifted tire.

I got around it by running a hand throttle on the shifter. That way I could clutch and brake with my feet and gas with my right hand. It worked pretty good.

Your going to lift a front tire more often than the back so you probably won't have that issue with it in the back.

check the front! You might have a pleasant surprise there as well!
 
IIRC with a TT you can just barely see the end of the worm gears from on side of the case when rotated just right.
 
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