Driving A Clutch Question

[mjtjnj]

Hey Guys-

Been away awhile.

Got a question, a little embarrassed to ask, so I can take the jokes.

I got this 87 MJ with the rebuilt 2.5, .030 over, roller rockers, header, runs really nice.

All of my other vehicles are stick shifts, and the Comanche gets the least driving of them all, as I finish the never-ending projects and plan on painting it eventually.

 

ANYWAY, it seems that the 2.5L in this heavy truck on 32's has a VERY narrow catch on the clutch.  When I had the engine rebuilt, I put in an ax-5 from a 2000 XJ and a new clutch, 25K miles ago.  I've had the truck for almost 10 years, so I don't remember much from when it was stock, but nowadays I'm always starving it when I take off in 1st.  Not major bucking, but you know that not-so-smooth feeling of taking off, like coming off the clutch too fast.  My other car, a monkey could drive, the clutch just grabs, and she goes. 

 

Have I lost my touch? 

Could I have done anything wrong on install?  The engine builder did machine my flywheel (didn't ask him to), even though they have the stamp on them NOT to. 

I know some guys install inertia rings on these trucks for off-roading, but my truck is strictly on highway.

 

Go ahead and laugh, I probably deserve it, but it's frustrating as hell! 

 

Any insight or opinions would be appreciated.  Not exactly tech, not exactly pub..... :rotf:

 

Tom

[zackcj7]

 It's a 4 cylinder so don't be afraid to rev it a little higher. What gear ratio are you running?

[92tanMJ]

 It's a 4 cylinder so don't be afraid to rev it a little higher. What gear ratio are you running?

Ive been worndering how 31's would do on my Mj..But I'm worried about the gear ratio being too low. So this would be my guess too low of a gear ratio ^

[JeepcoMJ]

4 cylinders "sweet spot" is at 3200 RPM.   that is where the hp and torque meet up on the same level.

 

Don't be afraid to rev it.

 

But I've got to say, your issue makes me think that you are running stock gears in it....a 4 cyl with 32's should be running 4.56 gearing.   4.10's is too light, and if yours was originally a 4 speed, then you have 3.55's, which would definitely cause the issue.

 

I'd say it's a gearing issue rather than a clutch issue.    My old 4 cyl 86 xj felt similar when i put 31's on it for fun, with 4.10 gears.    I ended up not putting the lift on, putting nice stock tires on, and getting rid of it.

[mjtjnj]

Thanks for the thoughts.  It has the stock 4.10 gearing.

I will try giving it a little more gas.  My mechanic friend said that AMC/Chrysler probably didn't want the flywheels machined, because they would be too thin, and subject to warping.  I've done some heavy pulling with the ol 4 banger, so maybe next time it's apart, I pop a new flywheel in there.

 

 

[JeepcoMJ]

you don't want the flywheels machined because they are concave and dished for the clutch to run appropriately

[92tanMJ]

Here's some good links for gearing info:

 

http://www.grimmjeeper.com/gears.html

 

http://www.experimentalinsanity.com/vehicle/resources/gearratios.php

^ according to this if youve got the ax5, 4.10s and 32s then you should be running okay on the highway, not every good around town. My guess is that with the gearing being kinda on the low side you don't have much torque, and (this is a guess could be completely untrue) that the machining could have made the catch on the clutch a little more narrow(er).. Someone correct me please, I'm just throwing out ideas..I'm new to this whole manual thing.

 

 

 

Not to thread jack, but I havent driven stick in probably 4 years, and that was for a month when I was 16...anyone have any advice for me on basically learning all over again? (I6 ax15)

[87Warrior]

Unlike the 4.0, the 2.5 flywheel CAN be machined. It is flat. No worries there.

 

I actually have the reverse problem. I daily drive my '86 MJ (2.5/ax5/95 XJ external slave/4.10s and 30" tires ). The clutch has a longer throw than my TJ does (4.0/3550/ 5.13s and 35" tires) so when I go to drive the TJ it takes a bit of relearning to get back into the groove. My '86 has plenty of power for the 30" tires with the 4.10 gears.

[JeepcoMJ]

the 2.5 flywheel is not flat in renix years.

[raviolli]

would it be possible your clutch wore out prematurely? ive got an '88 with a 2.5L with a ax-4...swapped out my 3.55 D35 for D44 and D30 with 3.07s that I plan to regear and I'm sitting on 32's as well. mud terrains as a matter of fact, and I have no problem with 1st. I've actually been able to spin the 32s coming out of 1st on loose pavement as surprising as that sounds..

[robbie95]

I just bought a 91 4 banger and mine is the same way. I just got it about 2 weeks ago and still trying to figure it out, the clutch is stiff and loves to spring back so you have to really have a good clutch leg lol... may be another problem but who knows..