Performance mods or re-gear??
JK Enthusiast
Joined: Nov 2008
Posts: 230
Likes: 0
From: Newbury Park, CA
If anybody wants an illustration of why you have to consider OD I've got one. I rarely drive my TJ but my wifes Park Avenue had to go in for service and I'm in the middle of installing PSC ram hydro assist steering on my JK so I hopped into the TJ to go pick her up. It's a 98 6 cyl automatic with 31" tires and 3.73 gears. Running down the freeway at 75 I was spinning 3100 rpm! Does anybody think that with the 4.0's torque curve that makes aany sense? If it had the JK's OD tranny, instead of it's 3 speed non OD unit, it would have been at 2100 rpm which would be far more appropriate. The damnest think is that the TJ probably weighs about 1500-2000# less than my 4 dr JK (fully loaded); yet the TJ gets 12.5 mpg at 75 and the heavier JK with OD gets 18 mpg. Yet with the Jk, because of it's OD, I can run 5.13 gears, which work far better off road than the TJ's 3.73's
I guess OD matters.
BTW - I've never seen a two-humped power curve on a chart of torque or HP on a dyno. Two power curves?????? Or are there three or four????? Do we have one for daily driving, one for economy, one for power and one for towing? All on the same engine? Reading some of these posts makes my head hurt. It's like explaining to one of our young engineers why his 200,000.00 job design won't work as well as the 5,000.00 job design we've been using successfully for years.
I guess OD matters.
BTW - I've never seen a two-humped power curve on a chart of torque or HP on a dyno. Two power curves?????? Or are there three or four????? Do we have one for daily driving, one for economy, one for power and one for towing? All on the same engine? Reading some of these posts makes my head hurt. It's like explaining to one of our young engineers why his 200,000.00 job design won't work as well as the 5,000.00 job design we've been using successfully for years.
I own an 08 Rubicon Unlimited AUTOMATIC that had 410 w/32" tires. I just changed the gears to 5:13 and kept the 32" and what a difference. On the freeway, I cruise at 65 with no problems. The Jeep stays in OD not screaming and shifting. No more pushing the pedal to the floor or trying to do the Flintstone's shuffle with my feet. It cruises at 2600 RMP at 65 MPH and my mileage show better than before. I went with the AEV per Mel's recommendation and I am still breaking in the gears slowly. Thanks for confirming Mel's outstanding Jeep upgrades.
I want to remind everyone that on 3-4% upgrades, it just cruises....
Thanks to everyone who suggested re-gearing....
JK Super Freak
Joined: May 2008
Posts: 1,279
Likes: 0
From: Grand Junction, CO
Chuck, you know what you are talking about and boy does Mel at Offroad Evolution-Fullerton, CA know how to set up Jeeps, WOW!
I own an 08 Rubicon Unlimited AUTOMATIC that had 410 w/32" tires. I just changed the gears to 5:13 and kept the 32" and what a difference. On the freeway, I cruise at 65 with no problems. The Jeep stays in OD not screaming and shifting. No more pushing the pedal to the floor or trying to do the Flintstone's shuffle with my feet. It cruises at 2600 RMP at 65 MPH and my mileage show better than before. I went with the AEV per Mel's recommendation and I am still breaking in the gears slowly. Thanks for confirming Mel's outstanding Jeep upgrades.
I want to remind everyone that on 3-4% upgrades, it just cruises....
Thanks to everyone who suggested re-gearing....
I own an 08 Rubicon Unlimited AUTOMATIC that had 410 w/32" tires. I just changed the gears to 5:13 and kept the 32" and what a difference. On the freeway, I cruise at 65 with no problems. The Jeep stays in OD not screaming and shifting. No more pushing the pedal to the floor or trying to do the Flintstone's shuffle with my feet. It cruises at 2600 RMP at 65 MPH and my mileage show better than before. I went with the AEV per Mel's recommendation and I am still breaking in the gears slowly. Thanks for confirming Mel's outstanding Jeep upgrades.
I want to remind everyone that on 3-4% upgrades, it just cruises....
Thanks to everyone who suggested re-gearing....
JK Enthusiast
Joined: Nov 2008
Posts: 230
Likes: 0
From: Newbury Park, CA
Chuck, Now I am looking for a good qualtiy Mesh top as I will be flying up the grades and hills and staying ahead of the trucks. THANKS.....
JK Freak
Joined: Feb 2007
Posts: 753
Likes: 0
From: NY
fewww...I just read this entire thread from start to finish...good stuf
f..The fight in the middle was also good. I do have a questioin that may have been partly answered. I have an unlimited auto, currently running 33's with 4.10's. Also have bumpers, winch and a bunch of gear...lotsa weight. Its a Sahara so it has the front Dana 30. I really want to install 5.13']s but worry about strength decrease with the weaker front axel. Heres the real killer...I have a great buddy who is a great mechanic and welder...done many gear swaps in CJ's..YJ's and TJ's... Old school..just never a JK. He will install the gears for very litttle $$$ and my help. But he refuses to install anything lower than 4.56 as he says I will be creating a great weakness. He has explained to me how the ring decreases drastically in size causing weakness...what should I do? Seems like theres a lot of guys running 5.13's with a 30 and havnt had any issues..I will be going to 35" tires relatively soon....Can I do the re-gear safely or consider doing the front axel first..The 30 has held up very well thus far.
f..The fight in the middle was also good. I do have a questioin that may have been partly answered. I have an unlimited auto, currently running 33's with 4.10's. Also have bumpers, winch and a bunch of gear...lotsa weight. Its a Sahara so it has the front Dana 30. I really want to install 5.13']s but worry about strength decrease with the weaker front axel. Heres the real killer...I have a great buddy who is a great mechanic and welder...done many gear swaps in CJ's..YJ's and TJ's... Old school..just never a JK. He will install the gears for very litttle $$$ and my help. But he refuses to install anything lower than 4.56 as he says I will be creating a great weakness. He has explained to me how the ring decreases drastically in size causing weakness...what should I do? Seems like theres a lot of guys running 5.13's with a 30 and havnt had any issues..I will be going to 35" tires relatively soon....Can I do the re-gear safely or consider doing the front axel first..The 30 has held up very well thus far.
JK Enthusiast
Joined: Oct 2006
Posts: 140
Likes: 0
From: Calgary, AB CANADA
