grumble at exactly 1900rpm

[calsbeek]

I bought my 1986 BJ74 about 2 months ago. Its running great, and I just drove about 7 hours back and forth to maine this weekend without a hitch, getting something close to 27 mpg.
however, I have noticed that when accelerating in 3rd and/or in 4th gear, as SOON as I hit 1900rpm, I pick up an extra rumbly grumbly sound from below. Can't tell if its engine noise or from the transmission, but its definitely consistently right at 1900 and then goes away when I get to 2000 rpm. Feels not-natural (a little more vibration comes along with the sound)

If I back off of the accelerator a bit it goes away, and if I accelerate through 1900 rpm while going gently down hill it is also absent.

any ideas?

 

[Mookies]

If it's anything like my well worn R151, the output shaft bearings wearing out produces the exact sound and vibration. First things first though, check the u joints and output shaft flange for play.

 

[calsbeek]

thanks for the start. I'll have a look there first. Either way, it doesn't seem like the shaft bearing would be a major repair...if I'm correct in assuming that I don't have to tear down the transmission to get to it?

 

[Burbot]

I would start with your shafts make sure no excessive play in splines or joints. Experiment what happens in low? Hubs in and out only happens under load from the sound of it. Took mine out today pulled over twice trying to figure a strange growl noise at 90 km. Was the mud flap I think. Sometimes two sets of ears helps. Windows open radio off. Sounds telescope so hard to figure sometimes. Good luck

 

[calsbeek]

Driving around town today i could not reproduce the sound. Weird. It was super consistent all day on that drive from Maine...

 

[JuanJ]

Hello,

Shafts are a good starting point. They might be in need of some grease. Check the grease ports in the spider gears. They play tricks when they run out of grease.

I assume you have the H55F transmission. This gear box slips gears with age and/or abuse. If yours does not, it is probably fine.






Juan

 

[Burbot]

Drive it till it breaks. Mystery solved. Or turn up radio lol

 

[roscoFJ73]

My 73 series had some rumbly noises. Just about everything mechanical on it died around 280000klms. I suspect the PO never changed the oil in anything. I replaced the rear diff and it got rid of some rumbling, and then the front diff which took some more out. Later I did the T/case and that got the last bit of rumbly.
I'm getting a touch of rumbly around 2000 in my troopy at the moment then it fades away.I get it everyday going down the freeway entrance Definitely feel like universals need replacing.

 

[calsbeek]

I've still only heard the noise now on that longish trip to Maine. Maybe the prolonger hi way speed had something to do with it?

I have replaced the fluids in the front and rear diff, the transfer case, the PTO, the transmission and the engine oil. It may be my imagination or just coincidence but I think the noise only showed up AFTER I changed all of the fluids.
At any rate, i will keep waiting to see if it comes back. Till then.....