sinat01
NAXJA Forum User
- Location
- Preston county, WV
stock gearing sucks on and off road. justify it how you want, but your opinion will change if you drive something geared appropriately.
Plus its less strain on the drivetrain
stock gearing sucks on and off road. justify it how you want, but your opinion will change if you drive something geared appropriately.
Awesome compression. Wouldn't waste time/money on a leak down, you have issues elsewhere IMOSo I just had a chance to look around the jeep and I pulled the spark plugs and they all looked great. Then I did a compression test:
#1-145
#2-155
#3-150
#4-148
#5-142
#6-140
So nothing crazy jumped out at me but if one of the parts stores has a lead down tester I can rent/borrow, I will do that tomorrow. I can double check my distributor is indexed right and make sure I have good spark on each cylinder and double check my fuel pressure tomorrow but if it all checks good like I think it will, I will be back to my original problem of something not being right. Any thoughts or suggestions? I know someone mentioned clutch earlier but it's brand new. I'm by no means a clutch or transmission expert, so is there a test to make sure the clutch is fully grabbing? I don't smell any burning from a burning clutch.
Dang. Why did I have to read this post today? I'm on 33's with stock gearing and I was close to content with it. Thought about regearing "someday."
Now I'm convinced that I'm not doing right by my baby unless I do it this weekend.
I don't have the time (or money) for this!!
This is doing 80 with stock gearing with 33X12.50r15
The OP is driving a manual according to posts concerning the clutch. This means the stock differential gearing is 3.05 iirc. For comparison stock automatic ax15 equipped differential gearing is 3.55. Thus there is a significant difference between going to 4.56 from the two different starting points. It's a difference of 28% gearing increase vs 50% increase. OEM tires were 28" tall tires. Going from 28" to 33" tires is an increase of 18%. Compare that to the gear ratio increases. 50% (gear increase) - 18% tire size difference = 32% higher gear:tire ratio over stock. The math isn't completely linear but it makes sense that you'd run higher RPMs by 1/3 to attain same speeds as stock configuration.
Another possibility no one has mentioned is the option that your phone based gps speed is wrong?
As discussed there are calculators online that will give you all the information for figuring out what RPM you should be running at what gearing ratio/tire size. More useful still are the various spreadsheet style charts showing gearing ratios needed to match stock performance. The better charts give the input data for what type of trans or even trans gearing were used for formulation which is useful.
questions...
- does the motor go through the full RPM range? by that i mean idle to rev limiter when in nuetral.
- what RPMs are you turning at 45 mph? both 4th and 5th.
- if you down shift can you power through the speed cap you are seeing in a higher gear?
and this is where my suspicion is...
- did you buy the rear axle or gear it yourself?
- and if you bought it, did you verify the gear ration?
assuming the motor and trans are in good health (its a 4.0 and AX15... either they work or they dont. lol), your issue screams tall gearing (low numerically). with 4.56s on 33s you should have no issues hitting 3k rpms and driving 80mph.
here is a pretty good calculator for you to take a look at:
http://www.grimmjeeper.com/gears.html