4.10 to 4.56/4.88. What to expect - JeepForum.com
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post #1 of 7 Old 06-17-2019, 05:15 PM Thread Starter
jhrebs
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4.10 to 4.56/4.88. What to expect

I am thinking about regearing. I have a 4 cylinder with stock 4.10ís. 4.5Ē of total lift in 33ís. What will I expect after? I get maybe better take off and will be able to use 5th gear again. But Iím referring more to off-road handling.


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post #2 of 7 Old 06-17-2019, 06:00 PM
Waternut
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I had that same setup except I had the 95 engine and I went with 4.88's. If you're unhappy with the power, you will still be unhappy after regearing. I rolled with the 4 cylinder with a mediocre attitude towards it. It was good enough and was pretty good offroad but it wasn't enjoyable to drive any faster than 60mph because it was so gutless. I would drive 3-4 hours on backroads to trails just so I didn't have to run on the interstate and get passed constantly. The 4.88's did make the drive nicer overall but it only took a little unreliability from the 4 cylinder for me to despise it completely and I did a V8 swap. For the record, I wasn't really unhappy with the 4 cylinders power below 55mph. Over that, it was miserable.

I really didn't notice any gains in acceleration mostly because I shift accordingly to keep up with traffic. You may end up shifting a few yards earlier than you did before....you will probably be shifting out of 1st before you get through every intersection. You will regain 5th gear on the highway but you're still going to have to downshift on every uphill and if it's steep-ish, you're still going to lose speed on that hill in 4th.

Offroad, you really won't notice a huge difference. 1st gear in low range will be incredibly slow and will allow you to crawl a little easier without having to ride the clutch as much and you may get impatient on downhills in 1st gear going 2 mph so I typically ended up shifting to 2nd and riding the brake a little to keep up with the group.
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post #3 of 7 Old 06-17-2019, 08:58 PM
JohnR1
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here are the numbers for the factory gear/tire and RPM you will be a 60mph and 4th gear.
4.10 gears with 205/75-15. 3050 rpm
4.56 gears with 33's 2873 rpm
4.88 gears with 33's 3075 rpm


if you keep your tire size the same and go from 3.73 to 4.56, you will gain about 500 rpm more. from 4.10 to 4.56 will get you about 250 more rpm.
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post #4 of 7 Old 06-17-2019, 09:14 PM
JeepinJeff72
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Quote:
Originally Posted by Waternut View Post
I had that same setup except I had the 95 engine and I went with 4.88's. If you're unhappy with the power, you will still be unhappy after regearing. I rolled with the 4 cylinder with a mediocre attitude towards it. It was good enough and was pretty good offroad but it wasn't enjoyable to drive any faster than 60mph because it was so gutless. I would drive 3-4 hours on backroads to trails just so I didn't have to run on the interstate and get passed constantly. The 4.88's did make the drive nicer overall but it only took a little unreliability from the 4 cylinder for me to despise it completely and I did a V8 swap. For the record, I wasn't really unhappy with the 4 cylinders power below 55mph. Over that, it was miserable.



I really didn't notice any gains in acceleration mostly because I shift accordingly to keep up with traffic. You may end up shifting a few yards earlier than you did before....you will probably be shifting out of 1st before you get through every intersection. You will regain 5th gear on the highway but you're still going to have to downshift on every uphill and if it's steep-ish, you're still going to lose speed on that hill in 4th.



Offroad, you really won't notice a huge difference. 1st gear in low range will be incredibly slow and will allow you to crawl a little easier without having to ride the clutch as much and you may get impatient on downhills in 1st gear going 2 mph so I typically ended up shifting to 2nd and riding the brake a little to keep up with the group.
Agreed. I had the exact same setup, 95 4-cyl, 4.10 gears to 4.88 on 33s. Before the gear change, I ran out of engine at 55mph & waiting for 55 was like watching grass grow. Moving to 4.88s, it was still a gutless wonder but I was able to attain highway speeds (70 mph).

And aha! I should probably message this idk. I, too, am in the middle of a SBC swap. I've heard the frame and motor mounts are different for the 4cyl YJs opposed to the 6cyl. I don't know if it's different also for strength reasons. Did you swap in a SBC? And did you have any issues with frame strength or motor mount positioning? Which mounts did you use? Thank you!

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post #5 of 7 Old 06-17-2019, 09:21 PM
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Quote:
Originally Posted by JeepinJeff72 View Post
Quote:
Originally Posted by Waternut View Post
I had that same setup except I had the 95 engine and I went with 4.88's. If you're unhappy with the power, you will still be unhappy after regearing. I rolled with the 4 cylinder with a mediocre attitude towards it. It was good enough and was pretty good offroad but it wasn't enjoyable to drive any faster than 60mph because it was so gutless. I would drive 3-4 hours on backroads to trails just so I didn't have to run on the interstate and get passed constantly. The 4.88's did make the drive nicer overall but it only took a little unreliability from the 4 cylinder for me to despise it completely and I did a V8 swap. For the record, I wasn't really unhappy with the 4 cylinders power below 55mph. Over that, it was miserable.



I really didn't notice any gains in acceleration mostly because I shift accordingly to keep up with traffic. You may end up shifting a few yards earlier than you did before....you will probably be shifting out of 1st before you get through every intersection. You will regain 5th gear on the highway but you're still going to have to downshift on every uphill and if it's steep-ish, you're still going to lose speed on that hill in 4th.



Offroad, you really won't notice a huge difference. 1st gear in low range will be incredibly slow and will allow you to crawl a little easier without having to ride the clutch as much and you may get impatient on downhills in 1st gear going 2 mph so I typically ended up shifting to 2nd and riding the brake a little to keep up with the group.
Agreed. I had the exact same setup, 95 4-cyl, 4.10 gears to 4.88 on 33s. Before the gear change, I ran out of engine at 55mph & waiting for 55 was like watching grass grow. Moving to 4.88s, it was still a gutless wonder but I was able to attain highway speeds (70 mph).

And aha! I should probably message this idk. I, too, am in the middle of a SBC swap. I've heard the frame and motor mounts are different for the 4cyl YJs opposed to the 6cyl. I don't know if it's different also for strength reasons. Did you swap in a SBC? And did you have any issues with frame strength or motor mount positioning? Which mounts did you use? Thank you!

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Check out the link in my sig. Doesn't matter what motor/transmission mounts you have when you go to a V8 because you're going to cut them all off completely anyway.


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post #6 of 7 Old 06-17-2019, 09:39 PM
blake989
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I took a 95 4 banger auto from 3.73s to 4.88s, and in my experience, the change was extremely noticeable. Went from unbearable to a jeep again.

Now I'll agree, there is no replacement for displacement, but OP, if you're curious about "off road" performance, yes, you will notice a difference. Think of it like this, you'll be like little log skidder.

And I'm sure you know, but the D35 isn't going to like you for doing this!

The YJ is no longer my DD. I have sacrificed all future retirement plans for jeep parts. I'm depending on social security!
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post #7 of 7 Old 06-18-2019, 07:11 AM
StanF
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I'm a former 2.5L owner, and I'm glad that I don't have it anymore. The main problem was headwinds or highway usage - it was just totally gutless with larger tires 32" (and was lifted, of course, so it caught more air). It was okay around town less than 45 mph, but that's not many of the miles that I drive. Of course, I never used 5th gear.

I thought about regearing, but in the end, I took the money and did an engine swap. I looked at cost of regearing (~$1000) vs the cost of a drivetrain swap ($big) minus the cost of selling existing good 2.5l drivetrain (~$1000). I just decided for the long haul to do the swap. I put in a 4.0L\AX15, which works well for me. Others will say that this isn't a worthwhile swap to do, which could be true for some people. If you can find a donor YJ, you'll be ahead of the game, as all the other parts (transmission, ECU, driveshafts, etc) add up to $$$.

4.10 gears + 32" tires + 4.0L\AX15 was a perfect combination. Very peppy and fun to drive - both onroad and offroad. (Your 33" tires would be the same)

Again, this worked well for me because of my needs and interests. Others love their 2.5L engines and will tell you to just regear and be happy with it. I'm just trying to get you to think about other options - it depends on your needs, budget, etc. If I was doing the swap today, I would probably look at LS swaps, like the common 5.3L.

If you are just looking for offroad improvement, a 4:1 transfer case is a game changer with the 2.5L engine. I swapped in a TJ Rubicon transfer case, and it was great offroad with the 2.5L. In case you are wondering the progression of my Jeep - it was done in stages:

2.5L \ AX5 \ NP231 \ 32" tires \ 4.10 \ front Dana 30, rear Dana 35

2.5L \ AX5 \ NP231 \ 32" tires \ 4.10 \ front Dana 30, rear 8.8

2.5L \ AX15 \ NP241OR \ 32" tires \ 4.10 \ front Dana 30, rear 8.8

4.0L \ AX15 \ NP241OR \ 32" tires \ 4.10 \ front Dana 30, rear 8.8

4.0L \ AX15 \ NP241OR \ 35" tires \ 4.88 \ front full width HP Dana 44 and rear full width 8.8


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