JL Crawl Ratios w/Auto Trans

[Non Partisan]

Holy mackerels! The crawl ratios of the 8-speed transmissions are near to a porcupine walk. Better than the old NAG1 used in the JK's.

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[KnG818]

Holy mackerels! The crawl ratios of the 8-speed transmissions are near to a porcupine walk. Better than the old NAG1 used in the JK's.

...and that's on 35's.

On 33's it's even better.(less clearance but better ratios)

Which is why people re-gear a lot with larger tires like 37" or bigger.

Engine is the other half of the equation, but let's keep it simple.

 

[SecondTJ]

Yep, the 4.71:1 first gear is also steeper than JK’s manual trans too!

That chart has the wrong gear ratios listed for 8HP75, they are the same as 850RE

 

[Non Partisan]

Here is a snip from the Wikipedia.org site giving gear ratios for the 8HP75/50:

 

[SecondTJ]

Here is a snip from the Wikipedia.org site giving gear ratios for the 8HP75/50:

FCA does not use those optional gear ratios.

 

[JIMBOX]

Don't forget---the CRAWL RATIO is a MECHANICAL DRIVETRAIN FIGURE--

Has nothing to do with TIRE SIZE !

W.E.

JIMBO

 

[KnG818]

Don't forget---the CRAWL RATIO is a MECHANICAL DRIVETRAIN FIGURE--

Has nothing to do with TIRE SIZE !

W.E.

JIMBO

It's a linear relationship.

...I understand your point.

 

[Non Partisan]

Don't forget---the CRAWL RATIO is a MECHANICAL DRIVETRAIN FIGURE--

Has nothing to do with TIRE SIZE !

W.E.

JIMBO

I agree with your statements. However, including tire size when calculating the crawl rate (= distance in time) is imperative. Four feet per second has its place as well as one foot per second, different terrains for sure.

The new version of automatic transmissions has given consumers increased crawling control, quicker acceleration and a little bit at the long end in the 8th gear. Having experienced the days of old, I am glad to see these improvements and welcome them to my rig.

 

[Non Partisan]

FCA does not use those optional gear ratios.

Can you point me to a source of FCA transmission gear ratios, will be appreciated.

 

[JIMBOX]

I agree with your statements. However, including tire size when calculating the crawl rate (= distance in time) is imperative. Four feet per second has its place as well as one foot per second, different terrains for sure.

The new version of automatic transmissions has given consumers increased crawling control, quicker acceleration and a little bit at the long end in the 8th gear. Having experienced the days of old, I am glad to see these improvements and welcome them to my rig.

Oh YEAH, I agree, but the phrase "CRAWL RATIO" is used for ENGENEERING to design/compare tranny 1st gear/difff. gearing/xfer case gears, for construction/article--

Of course the TIRE SIZE will finalize the RATIO-INDIVIDUALLY !

JIMBO

 

[SecondTJ]

Can you point me to a source of FCA transmission gear ratios, will be appreciated.

FCA has used the same gear set since 2014

https://media.fcanorthamerica.com/newsrelease.do?id=15719&mid=

The TorqueFlite family shares these gear ratios:

• 4.71
• 3.14
• 2.10
• 1.67
• 1.29
• 1.00
• 0.84
• 0.67

 

[Non Partisan]

@SecondTJ Thanks for taking the time to post the website of your reference. Unfortunately the article is 5+ years old. Why in the bee geezuz won't they disclose that information more readily. In any event, the information presently out there is close enough to aid in planning gears and such.

Ya gotta hand it to the older CYT/J models for being light and nimble. If we had those 8-speeds available 30 years ago there woulda been less expense in modding our rigs. The one feature that is a game changer in the auto transmission is the downhill descent. Lacking that in an auto kept a lot of us in the NV 5-speed manuals for a long time.

Throw a 3.0 ecodiesel with the 8HP75 into one of your TJs and rip it up.

 

[SecondTJ]

Unfortunately the article is 5+ years old. Why in the bee geezuz won't they disclose that information more readily.

Here...

https://s3.amazonaws.com/chryslerme..._JP_Wrangler_SPmrgun0frgq245rkio8imc5var6.pdf

 

[Arrowhead]

FCA thought the ratio was low enough that in 4L the auto defaults to 2nd gear from a standing start. I often drop down manually to 1st for more control.

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