42RLE Overdrive Questions

It gad 3.73 when I bought it 12 years ago. I put in 4.56 a couple years ago.
My wifes yj has 3 speed auto, 4.10s, 35s. Cruises at 3000 rpm at about 60 mph. Blew a rod, complete with a hole in the block when she was on freeway going 65 mph. That was several years ago.
So. I try to keeps rpms down on our 4.0s.
Something is off with your numbers. You should not be hitting 3k until around 75 with that combo.
 
It gad 3.73 when I bought it 12 years ago. I put in 4.56 a couple years ago.
My wifes yj has 3 speed auto, 4.10s, 35s. Cruises at 3000 rpm at about 60 mph. Blew a rod, complete with a hole in the block when she was on freeway going 65 mph. That was several years ago.
So. I try to keeps rpms down on our 4.0s.
If that RPM was conducive to throwing rods out the side of the block, Jeep would not have shipped 100's of 1000's of them with 3.73's, the 32RH, and 29" tires. Simply would not have. In other words, something else was the cause of the rod saying hi to the outside world and a steady diet of 3000 RPM wasn't it. BTW- your RPM at 60 seems a bit off. The 68mph RPM of the 32RH is 3000 in the TJ. That is how Kat's rig was from the factory, how it was when I put 35's on it with 4.56's. I didn't have to change the speedo gear to fix the MPH.
 
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So do I, I would have liked to have regeared to 4.56 after converting to the 32RH to bring the rpms down to 2700-2750 at 70 mph. My only point was to say that your 3k cruising rpms were not the reason the engine threw a rod. The engine does perfectly fine at those rpms which are only 57% of its max rpms. :)
The 04 that you have ridden in has 208 on it and it never runs below 3K practically anywhere I drive it.
 
High RPM isn't what kills engines. High load is what kills engines. If you are constantly putting your foot down to get up to high RPM, then your engine might not last too long. A light right foot goes a long way, but that doesn't mean you can't rev the engine up a bit.

My TJ with 227,000 on it has always been driven at "high" RPM (shift at ~3300) but it has never been beat on with repeated foot to the floor acceleration. Every single thing internally on the engine is the same as it was when it left the factory.
 
Well. Kids. I'll take the YJ out for a spin tonight. It's due to get driven anyway and I've got the time. Take it up to 60, 65, watch the Tach. I'll even gps it for speed acuracy. Maybe video it for the hell of it.
I"ll get back to ya.
 
Thanks for your response guys now I know it’s safe to always drive with the overdrive off that gives me time to plan and save for new gears I also want to put lockers in at the same time but I need to work out what tire size to go with I would like to go to 33 or 35 but as ridiculous as it may sound over here in the land of Oz we need an engineers certificate to go up to those sizes but I don’t know how easy hard or how much they are to get


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Thanks for your response guys now I know it’s safe to always drive with the overdrive off that gives me time to plan and save for new gears I also want to put lockers in at the same time but I need to work out what tire size to go with I would like to go to 33 or 35 but as ridiculous as it may sound over here in the land of Oz we need an engineers certificate to go up to those sizes but I don’t know how easy hard or how much they are to get


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Wow! That’s a lot of work just to put on bigger tires! Good luck, let us know what you decide/plan to do.
 
I have a two part question I have the 42RLE with 3.73 gears and 31in tires and I was wondering if it would hurt if I always drive with the overdrive off? and if so is there a way to rewire the switch so that the overdrive switch default is off so that I don’t have to switch the overdrive off every time I start my Jeep?
cheers Peter
I have the same setup in my Jeep. I have my reasons for turning off the OD, what is your reason?

Scott
 
Hi Scott the reason I switch my overdrive off is that is that I feel that the final drive ratio is just too high and the rpm’s are too low so that the motor seems to be Laboring a lot




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