I recently added a 2.5" lift + 33's and am now noticing that my transmission is "slipping." It started right after I put the 33's on. Right around 40 mph, it's like the Jeep can't decide which gear it wants to be in. When I hit 40, it shifts up a gear and the rpms drop to 1100, then if I barely touch the gas, it jumps up to 2300 and then quickly and abrubtly drops back down. I know this sounds normal, but trust me there's something noticeably wrong. It's real erratic. Also If I'm in cruise control, say at 65 mph and try and increase to 70, it drops a gear, speeds up 1 mph and then drops another gear, almost redlines into 4800 mph and speeds up some more... super erratic and nowhere near smooth gear changing. Otherwise it runs fine, no noticeable clunks, clanks, grindng etc.. I do get a "clunk" sometimes when I shift into reverse on a boat ramp, but have always had that. Any input or suggestions???

 

I noticed a change in o/d, cruising at 70+ as it will kick in and out of o/d whenever I hit a hill but I've never had the problems you are having. It's not normal. I'd have it checked.

 

You don't give much info on your Jeep. What size tire did you have before?
You said yourself what brought on the problems. Have you given any thought to the fact the tranny and computer are confused because your tires are turning at a different speed now? Internal rpm, road speed, and load are different from what is expected.
If your tires are bigger than stock, have the computer recalibrated for tire size.

 

I have a 2008 JK 4wd and it used to have the stock 32's. I have definitely given that some thought, but hadn't read where others have found it necessary in any other threads I came across. Is that something I can get done at the dealership or should I get it done at an alignment place or something without getting gouged at the dealer?

 

Your computer is seriously lost.
You've done these upgrades and forgot to tell computer about them, and a re-gear wouldn't hurt.
I lost over drive on the highway, re-geared and got it back.
Before I re-geared the shift points where erratic.
Hypertech power programmer heals some of these symptoms, tire size gear size etc.
You are not done spending money yet.

 

Yep, exactly as southbaydog suggested. Shift points are determined by three things, throttle position, rpm and speedometer. If the speddometer isn't right your going to send the PCM into hunting for the right gear without a road map.

Once you get your speedo re-calibrated via AEV ProCal, Hypertech or Superchips Flashpaq, then you have a stable platform for the selection of the appropriate gears.

 

Sweet. I ordered one up today. Thanks alot! Not sure how I missed this detail in all of my lift/wheels/tires research!

 

You're welcomed. Glad I could help.

 

Don't forget to re-gear!

 

From reading your post you have an auto. Probally with 3.73 gears. I went through this same thing. I went from 29in stock tires to 33in trxus M/Ts. I had the constant shifting in and out of o/d. I also did reprogrammed the computer for the tires. I will tell you that you will still have the same problem unless you can change the shift points.

Which unless the hypertech or the AVEPro have added this feature to their programmers. You will not be able to change them. Only on the six speed trans can you change the shift points with the programmer.

So if you are going to do any wheelin or just want more power. Regear to no less than 4.56s if you are going to stay with 33s. If you even think of going to 35s later down the road. Just regear to 4.88s and be done with it.

This may seem like a big jump in gears, but trust me it isnt. I change from 3.73s to 4.88s which I got from Dave at Northridge 4x4. This was the best thing I did. More power, its is not shifting in/out of overdrive. I still get approx 330 miles to a full tank. At 65 mph my rpms are approx 2300 rpms. And this is where the JKs like to be.