Gearing for 35s 4.10? - JeepForum.com
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post #1 of 31 Old 07-26-2020, 07:09 PM Thread Starter
RedRaiderCJ7
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Gearing for 35s 4.10?

Is anyone running 4.10s with 35s? (with a 258) It sounds like 4.56 is the ticket for 35s and the 258 but I intend to do an engine swap later that would favor lower (higher*?) gearing. Looking to buy some new Dana 44s from ECGS and only want to feel that pain once and not have to regear. Just curious how 4.10s behave with the 258 and t5 as that seems to be right in the middle for the two motors I'll use. Thanks.

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post #2 of 31 Old 07-26-2020, 08:25 PM
alabamabuddog
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I have 3:54's running 35's
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post #3 of 31 Old 07-26-2020, 09:07 PM
REDnBLUES
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You wont be running a T5 long with 35's. I tore one up with factory 235's when new.

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post #4 of 31 Old 07-26-2020, 11:10 PM
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In 4th with true 35" diameter tyres you will be running at 2100rpm at full cruise on the highway at 60mph with 4.10:1 gears. The rig will struggle a little with your big tyres but this is about where a 258 in top gear should be!!

Why do I say that? You do not a large amount of torque in a 258, peak torque is at about 2400 rpm and drops off after that, if you can keep it in a sweet spot just below peak you can have a trailing throttle (good for fuel consumption) and more to go, it will respond when you need it.

Put in overdrive 5th and 14% reduction in gearing and that is only 1800rpm. The poor thing will want to throw a rod, you will be constantly dropping down to 4th in search of more torque!!!

So I would not suggest this setup for a 258. The 4.56:1 gears will bring 4th up to 2400rpm and 5th 2100rpm. This is more manageable on highway with the 258 and big tyres and will bring 1st down a bit as well. The T5 does not have an especially deep gearing (1st is 4.06:1) so you may want to have a useable 5th gear and bring everything down a bit.

Of course I would not recommend a T5 with a more powerful engine and big tyres. You may want to look at a different transmission and reassess.

Question then is whether the new engine will be happy at cruise at a mere 1800rpm, and whether you could survive in the meantime by using the T5 as a T4. Not knowing what you want to put in, and how much torque it develops at low rpm, hard to say. If you were to tell me a large V8, the 4.10 would be fine.

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post #5 of 31 Old 07-27-2020, 07:35 AM Thread Starter
RedRaiderCJ7
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Thanks fellas, that's very helpful. The t5 would be replaced by an ax15 when I replace the motor, but I wanted to ride this set up for 4 or 5 years if I could and would rather not have to regear later. It sounds like this may be manageable but not enjoyable so I may rethink it. Would it help much if I put on 315s (34.4"ish)?
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post #6 of 31 Old 07-27-2020, 08:52 AM
jurgen24
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Gearing for 35s 4.10?

Quote:
Originally Posted by BagusJeep View Post
In 4th with true 35" diameter tyres you will be running at 2100rpm at full cruise on the highway at 60mph with 4.10:1 gears. The rig will struggle a little with your big tyres but this is about where a 258 in top gear should be!!

Why do I say that? You do not a large amount of torque in a 258, peak torque is at about 2400 rpm and drops off after that, if you can keep it in a sweet spot just below peak you can have a trailing throttle (good for fuel consumption) and more to go, it will respond when you need it.

Put in overdrive 5th and 14% reduction in gearing and that is only 1800rpm. The poor thing will want to throw a rod, you will be constantly dropping down to 4th in search of more torque!!!

So I would not suggest this setup for a 258. The 4.56:1 gears will bring 4th up to 2400rpm and 5th 2100rpm. This is more manageable on highway with the 258 and big tyres and will bring 1st down a bit as well. The T5 does not have an especially deep gearing (1st is 4.06:1) so you may want to have a useable 5th gear and bring everything down a bit.

Of course I would not recommend a T5 with a more powerful engine and big tyres. You may want to look at a different transmission and reassess.

Question then is whether the new engine will be happy at cruise at a mere 1800rpm, and whether you could survive in the meantime by using the T5 as a T4. Not knowing what you want to put in, and how much torque it develops at low rpm, hard to say. If you were to tell me a large V8, the 4.10 would be fine.

Your RPM calcs seem off, try

http://www.grimmjeeper.com/gears.html

35”, 4.1 in 4th at 60mph it should be 2362.




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post #7 of 31 Old 07-27-2020, 09:03 AM
jurgen24
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Quote:
Originally Posted by RedRaiderCJ7 View Post
Thanks fellas, that's very helpful. The t5 would be replaced by an ax15 when I replace the motor, but I wanted to ride this set up for 4 or 5 years if I could and would rather not have to regear later. It sounds like this may be manageable but not enjoyable so I may rethink it. Would it help much if I put on 315s (34.4"ish)?

That size won’t make much difference. The ideal gear ratio will depend on what you want your cruising speed to be and if you will have a 5th gear or not.


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post #8 of 31 Old 07-27-2020, 11:38 AM
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35's, T-5, 4.88's. Seems to do well, and at 65mph, RPMs are good. I won't be doing more than 65mph anyways. Been running this way for a couple years after having 33's its whole life.
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post #9 of 31 Old 07-27-2020, 12:32 PM
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Quote:
Originally Posted by alabamabuddog View Post
I have 3:54's running 35's
I bet your performance sucks. A number of years ago I ran 33's with 3.54's and it was just geared up too high.
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post #10 of 31 Old 07-27-2020, 02:05 PM
whodatschrome
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4:56's were right on the money for me when i had a 258/T5 combo with 32" tires. With 35's and a 5 speed, i'd be gearing down to a minimum of 4:88's. 5:13's would probably even be better. But all that goes out the window depending upon what terrain your driving on. If it's just concrete and and tarmac, then just leave in the 3:54's and plan not to use the 4th or 5th gears in the tranny.
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post #11 of 31 Old 07-27-2020, 03:25 PM
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I have 4.56’s and a T5 with my 35’s and a slightly warmed over 258
On the highway it’s just about perfect
In the woods the D300 is about right but for serious rock crawling I need a 4:1 gearset

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post #12 of 31 Old 07-28-2020, 04:09 AM
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Quote:
Originally Posted by jurgen24 View Post
Your RPM calcs seem off, try

http://www.grimmjeeper.com/gears.html

35”, 4.1 in 4th at 60mph it should be 2362.




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Yes, you are right. My tables are set up for 55mph!!!!

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post #13 of 31 Old 07-29-2020, 05:34 AM
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I would opt for the 4.56 set for a an overdrive rig seeing a lot of highway miles. 4.88 would be a bit lower and a better number for technical offroading. Both will improve the first gear ratio over the 4.10's, which is just as important as the final drive RPM's.


Popular/stock usable gear ratios have been 3.50, 3.73 4.10, 4.56. and 4.88. With the brief Jeep exception in the 60's and some early Scouts, the 4.27 ratio's are glaringly missing, leaving a big hole between 4.10 and 4.56, Which would be the sweet spot for 33" tires.

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post #14 of 31 Old 07-29-2020, 10:39 AM
LumpyGrits
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35's w/5speed, go with 4:88.
You'll really need to upgrade your brakes!
Gary

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post #15 of 31 Old 07-29-2020, 09:59 PM
BagusJeep
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LG is right, plenty of things to modify if you want to cruise with the big lift and big tyres.

I am very happy with 31" tyres on my CJ7s, the extra 2" under the diff would takes a toll on everything else, including your wallet.

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