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Any tips? This is like doing heart surgery through a butt hole me thinks. The shaft is wobbling right now. I can see it by watching the pulley. easier to just buy the crankshaft kit from autozone? Still doesn't look like too bad of a job really. my poor poor beloved jeep. either fixing it or Im getting rid of it. but the jeep prices right now are out of line. hate to, I just replaced the hub bearings and u-joints.
the thing is, I always replaced my own oil, but about a month ago I got lazy and took it in, since then the oil pressure has been funky.
after 10 years or so of ownership, shes starting to fall apart.
 

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It can be done but the thing to check are the crank journals. If some how only the bearings wore out you could just put new ones in. However the likely hood of that is slim I would say you would have to have have the crank turned and put in oversized bearings. However if you are observing all of this from the pulley I would tend to think this is not your problem. If your crank was wobbling enough to where you could see it I would think your engine would be coming apart. Check your pulley to see if it is bent.
 

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Pull #1 main bearing cap(first one behind crank pully), clean oil off journal and bearing insert, then plasti gauge it....Examine bearing and journal while you are at it for scoring and wear.

If you are driving a 4.0 six, and #1 is wallowed out, just pull it out and do master overhaul cause that bottom end is a stout as the old 240/300 ford six where just the front bearing alone can't cause crank wobble...A Jeep 4.0 crank is VERY well supported by plenty of main bearings.

First look to see it front crank oil seal is leaking...A wallowy crank will beat it out in short order/especially an older engine where oil seal has hardened.....Don't worry too much it pully 'seems' out of round as it spins providing it is well fastened to crank and rubber dampner(if installed) is good.....I ain't looked at my TJ 4.0 crank pully, but many I've dealt on especially Fords with had a rubber sleeve moulded in tween inner pully and outter pully...had several fail cause rubber went south from age.
 

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Discussion Starter · #4 ·
A mechanic told me the bearings were bad. I dont know enough to question him. I had my suspicians that maybe the pulley was bent on its own. if the crank is moving around enough to wobble the shaft, then I would think that should affect the rpms at the very least at idle. which are fine. I didnt want to have the whole crank machined down. which is why I was considering the rebuilt assembly from autozone. this is on a 2.5 this on my daily driver. later today I will unhook my belt and do a preliminry survey. a few months ago I threw a rebuilt alt on. wondering if I tightened the belt too much. hmmm.
 

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There is no way the belt could be tightened enough to mess with main bearings. Water pump bearings would fail long before anything else.
 

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Discussion Starter · #6 ·
A really stupid question, but what is a plastic guage? Im gathering all tools I need to do the job.
 

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Plastigage

Technology Electronic device



Paper Finger Material property Hand Table


Take a little piece about 1/2 to 3/4 long.
Place it on the bearing.
Torque cap back on.
Don't move anything.
Remove cap.
Using the gauge on the paper. See what it matches up to.

It's not perfect. But will give you a good idea what you got
 

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It should be doable. I take off all the main bottoms first then you can rotate out the top half of the bearing. Reassemble all mains finger tight at first then do rods. I do all final torque at the end.
 

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OK, Thanks. My preferred option is to replace the '97 2.5 with a 4.0. Anyone know if that is doable (using the same transmission and motor mounts and radiator and computer and fuel injections system [well of course the fuel injection system will have to be changed]). As many may recall, there was no "96 Jeeps and when I bought my Wrangle the 4.0 was not being manufactured and I needed a car right-a-way. I have always wanted the 4.0 (or even a 350 chevy, but that is way too complex for me).
 

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Anyone know if that is doable (using the same transmission and motor mounts and radiator and computer and fuel injections system [well of course the fuel injection system will have to be changed]).
It would be a challenge for a four cylinder computer to control a six cylinder engine.
 

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It would be a challenge for a four cylinder computer to control a six cylinder engine.
It would be hard pressed to figure out what to do with the extra two cylinders...
 

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Replace a 2.5 with a 4.0

OK, Thanks. My preferred option is to replace the '97 2.5 with a 4.0. Anyone know if that is doable (using the same transmission and motor mounts and radiator and computer and fuel injections system [well of course the fuel injection system will have to be changed]). As many may recall, there was no "96 Jeeps and when I bought my Wrangle the 4.0 was not being manufactured and I needed a car right-a-way. I have always wanted the 4.0 (or even a 350 chevy, but that is way too complex for me).
 

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The 350 might be the easier option, depending on emission laws where you are. You'd need the 4.0 computer, to manage the fuel injection. You'll have to change the transmission, because the 4 cyl transmission won't survive.

Not sure about the motor mounts, but the transmission mount is probably the same. The radiator is probably also the same.
 

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Your problem is not a bad main bearing..... If it was your engine would be knocking like crazy.

Its more likely a dampener that is coming undone.
 

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Blackbox19, what dampener are you talking about?
You are right about the knocking. There is none. When I start the engine it the oil pressure is around 40 to 45 psi. After running about 30 minutes it drops to around 20 while driving BUT at a traffic it drops to PANIC! Increase the RPMs and the pressure goes up (think goodness I have a manual transmission).
 

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Blackbox19, what dampener are you talking about?
The harmonic balancer. (Same one you were asked about in post #11.) That would be the "pulley" on the front end of the crankshaft. There is a layer of rubber that fails and allows the balancer (aka damper) to wobble. I would recommend that you check for a difference in axial runout between the inner and outer sections of the balancer.

After running about 30 minutes it drops to around 20 while driving BUT at a traffic it drops to PANIC! Increase the RPMs and the pressure goes up .
That is consistent with a clogged oil filter in which the bypass opens at higher rpm. I just dealt with that very issue last week. Oil change and new filter solved the problem.
 
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