Are these RPMs normal for a 32RH?

[jjvw]

And measure your tires. Not all 33" tires are exactly 33. I have 35" BFGs and they're 34.5". My wife's Mickey Thompson 35s are 33".

-Mac

If he is going to do that, then he needs to hold a tape measure from the ground up to the axle tube. Where the tape touches the tube is the center hub height. Double that number for the effective rolling diameter.

A horizontal measurement is not what we really looking for.

 

[Jellis]

33’s and 4.11 gears would end up right at 2400 rpm at 55 mph. It’s probably a slight discrepancy in the speedometer and you likely have 33’s and 4.11 gears. We can’t help any more than that with the limited info. 33’s actually are around 31.5” large and my calculations reflect that.

It can’t hold the same rpm from 50-65 mph, that makes no sense.

I will download a speedometer app and get back to you all. I'm telling you all though that from 55-65 if I increase speed slowly and steady it stays around 2500. If feels like a transmission that has overdrive and it's not shifting to overdrive, yet this tranny doesn't have overdrive

 

[jjvw]

I will download a speedometer app and get back to you all. I'm telling you all though that from 55-65 if I increase speed slowly and steady it stays around 2500. If feels like a transmission that has overdrive and it's not shifting to overdrive, yet this tranny doesn't have overdrive

Google Maps tells you your speed.

 

[machoheadgames]

Agreed. The effective rolling diameter measured from the hub height X2 would be close to that.

As would the rev/mile feature of most tires being around 630-640.

 

[jjvw]

As would the rev/mile feature of most tires being around 630-640.

Tire manufacturers do not know what PSI we run

 

[KennethS]

If feels like a transmission that has overdrive and it's not shifting to overdrive

I don’t know what that means. A 4 speed overdrive transmission that doesn’t shift into 4th gear is just not shifting into gear. You said you feel it shifting to 3rd gear. So I don’t know what you mean by that statement.

 

[hear]

I will download a speedometer app and get back to you all. I'm telling you all though that from 55-65 if I increase speed slowly and steady it stays around 2500. If feels like a transmission that has overdrive and it's not shifting to overdrive, yet this tranny doesn't have overdrive

Pics or it didn't happen. Post a video and lets see what's going on.

Otherwise I'm calling the Thermodynamics Police.

 

[Jellis]

I don’t know what that means. A 4 speed overdrive transmission that doesn’t shift into 4th gear is just not shifting into gear. You said you feel it shifting to 3rd gear. So I don’t know what you mean by that statement.

It is a 3.73 gear

 

[Jellis]

I will download a speedometer app and get back to you all. I'm telling you all though that from 55-65 if I increase speed slowly and steady it stays around 2500. If feels like a transmission that has overdrive and it's not shifting to overdrive, yet this tranny doesn't have overdrive

It is a 373 gear

 

[jjvw]

It is a 373 gear

Then if your tires are a 33", the Jeep should be close to this...

32rh/31.5"/3.73=2387rpm @ 60mph

 

[Jellis]

Then if your tires are a 33", the Jeep should be close to this...

32rh/31.5"/3.73=2387rpm @ 55mph

Thanks. So maybe my torque converter is staying locked up? I'm running 2500 rpm

 

[jjvw]

Thanks. So maybe my torque converter is staying locked up? I'm running 2500 rpm

2500rpm at what speed? And is that an accurate speed?

 

[Jellis]

2500rpm at what speed? And is that an accurate speed?

Im going to get back with you on this. Going to make sure I give you Accurate info

 

[hear]

The hardest one to get right is the tire size. Ignore what it says on the sidewall and instead measure from the ground up to the center of the wheel. That's your actual rolling radius, and it will be less than what your tire says.

 

[hear]

Thanks. So maybe my torque converter is staying locked up? I'm running 2500 rpm

You'd stall if it was staying locked up. But the easiest way to tell if locking up is a problem is to just unplug the TCC from the back corner of the trans and see if it does anything different (other than throwing a P0743).

 

[jjvw]

Im going to get back with you on this. Going to make sure I give you Accurate info

To achieve 2500rpm at 60mph, your tires will have a effective rolling diameter of 27.5" or a hub height of 13.75".

Or you have 4.27 gears.

Or your speedometer is not accurate.

 

[KennethS]

Then if your tires are a 33", the Jeep should be close to this...

32rh/31.5"/3.73=2387rpm @ 60mph

2400 RPM calculated is very close to the reported 2500 RPM. That 100 RPM difference is probably tachometer tolerance and eyeballing the needle position.

 

[jjvw]

2400 RPM calculated is very close to the reported 2500 RPM. That 100 RPM difference is probably tachometer tolerance and eyeballing the needle position.

Maybe so. Though it is valuable to understand that tire dimensions and gearing can and do make the numbers change quite a bit.

 

[Jellis]

Thanks for all the help on this one guys. Unfortunately the tranny is messed up again not even a week after the rebuild. The shop thinks it may need a valve body for the tranny, thet are tearing it apart again. Any suggestions on where to find a valve body for a 32 hr (904) transmission?

 

[hear]

I would be interested to know what about it is messed up.

I shopped VB's for the YJ flavor of this transmission, and I found TONS of variations in the valve body & transfer plate. If it were me rebuilding it myself, I would probably get a used VB off ebay motore and hope for the best. Swapping out the VB is not really that hard, just messy.