Too many RPM's

[007]

I'm curious. My Jeep has a stock AMC 304 auto and QuadraTrac . When I'm going down the highway at 55mph (verified with gps) I'm running 2900 RPM. That seems like a lot. I'm running 235/75-15 tires on stock wagons. I know it's in third because at lower speeds I've dropped it to second and you clearly feel it shift. Does the TA not lock on these? If so how? Or could my stock tach be off?

 

[IOPort51]

What is your axle ratio??

 

[derf]

What is your axle ratio??

My guess would be 4.27s since the math works out to 4.29...

But it really sounds like that Jeep needs taller tires or taller gears.

 

[007]

I have no idea what the ratio is. I've looked everywhere on this darn axle and can't find the code.

 

[CJ]

I have no idea what the ratio is. I've looked everywhere on this darn axle and can't find the code.

007 - please follow the guidelines below for your gear ratio identification.

-->> How to tell what gear ratio is in your CJ. - Jeep-CJ Tech. Articles

 

[007]

I thought that the AMC20 had a code on the case just to the right of the cover?

 

[CJ]

I thought that the AMC20 had a code on the case just to the right of the cover?

Read my article - please!

 

[mtnwhlr]

It is doing that because you have a set of low gears in it. Try running some 31-10.5 tires it will help and make it look better. I wish mine had gears like that in it I would be running some 33's

 

[007]

It will be next week before I can confirm the ratio; but after doing some more testing and paying more attention I'm 90% sure it's a 4.10.

So even with 32x11.5x15 tires I'd still be running 3200RPM's at 70mph and that's still a bunch I'd think.

SO, since this QuadraTrac has the low-range shifter, could I just go to a 2.72 or 3.31 and be good for simple trails in low range and keep low RPM's regardless of tire on the highway? Can I even get 2.72 or 3.31's for my Dana 30 front or would I have to settle for 3.54's?

 

[computeruser]

The RPMs with the 32" tires sounds about perfect for a mixed-use Jeep.

 

[007]

So I blocked the fronts, put it in neutral and jacked up the rears, marked the driveshaft and began to spin the rears...

At first bump, both spin the same way, but then they spin opposite and the driveshaft only moves an inch or so then never moves again...doesn't matter which way you spin the rears or which rear you spin.

Is this because it's a QuadraTrac and it's trying to engage the front diff since the rears are spinning?
I am / was pretty certain that this thing had a trac-lok based on the small thumps/tire-slips I feel when turning, but the opposite motion of the rears would negate that belief. I guess I'll need to pull the cover - but how can I tell if it's a trac-lok when the cover is pulled?

Based on every calculation I can find this is a 4.10 rear end (unless there's some torque lockup that's not locking - is that possible?), which means I either need to re-gear or run 32's it would seem.

I plan on driving this thing some on the Interstate for some distance and I don't want to have it wound tight all the time...