Hello all,

This is my daughters truck - '99 4x4 5.9 / 46RE. I replaced her trans last weekend with a good used unit and it runs, shifts, drives fine. I adjusted the TV cable which only took a very slight adjustment and that was the only adjustment I have made as the gear shift selector seems to shift fine. I also flushed the aux cooler both ways with Kooler Kleen. There was a bit of old trans fluid in the new (to me) converter and the total fill was about 9 qts. No noises, under normal conditions. The trans fluid looks to be a little overfilled - maybe 1/2" on the dipstick, if that. When removing the old trans, I snapped the front (return??) hard line at the trans so I flared the metal tube and patched it with 400psi trans hose; which is not kinked but does have about a 70* bend coming out of the trans body and onto the hose. New hard line is on order.

I'm hearing an odd, slight noise only under heavy acceleration after about 3k RPMs which I can only describe as what sounds to be some type of hydraulic pressure/fluid/maybe restriction kind of sound. Not really a hi-pitched slight squeal sound but maybe lower pitched? Under normal and 1/2 throttle driving, maybe more - no sound. Only when getting the RPMs higher and only while under heavy throttle. To test, I drove it in 2nd at about 4k RPM, normal throttle/no noise but was able to duplicate the sound if I varied the throttle pressure between normal and heavy, all while the PRMs were still around 4k - if that makes any sense. When the RPMs go up, this noise increases but I notice no abnormal shifting.

I get the feeling it might have something to do with pressure or perhaps a partially blocked vent tube? Could the trans being slightly above the full mark maybe have something to do with it? Maybe my rubber hose fix where I snapped the steel trans line? It does seem to sound like a "pressure" thing but I'm not certain. For starters, I'm going to bring the level to where it should be. I'm familiar with the gov. press / temp solenoid issues as this we have a Jeep ZJ and have had a Dodge 2500 / 47RE but am not sure if this noise could be associated with either of those.

Any input would be greatly appreciated.

Thanks,
Mikey

 

Probably has to do with the cooler line, but, even so, Given the conditions the problem presents itself, it seems like a non-issue to me...... For likely 99.999999% of her driving, she will never see 4K RPM in any event.

 

Thanks Hey You, I appreciate the reply. I just took the fluid level down to where it is not overfilled, it is now within the safe range of the dipstick. I also took it for a test drive and the more I listened, the more it seems like it's maybe coming from behind the dash. Her dash is broken and cracked (as are or were most of ours) so maybe that has something to do with sound amplification. The original radiator was plugged up a good deal so I replaced it but did not replace the heater core. I wonder if my mind is playing tricks on me by thinking that it's the trans when it may be a restriction in the heater core. Anyone ever hear any sound like that from the cooling system? I suppose I could reverse the heater hoses at the firewall and try it. Thoughts?

Thanks again,
Mikey

 

I wonder if what you are hearing is actually one of the actuators for the HVAC system losing vacuum....... These trucks are notorious for that type of behavior at higher RPM...... (thus, low vacuum.)

 

Dude.. you may be onto something.. I wish I could describe the sound more accurately but from what you said, it does sound like it could be air rushing through a small tear in a vacuum diaphragm or something similar. It's just not high pitched BUT it does change in volume and not pitch with throttle pressure so what you're suggesting could be completely possible. So what's a quick test? disco and plug the small, hard, vacuum line coming through the firewall? That's what feeds the actuator pods, correct?

 

That would work. Careful with those lines though, they dry out and get really brittle with age.

 

True. So no luck. For testing purposes I disco'd all vacuum coming from the intake manifold going to the cruise control pod and into the cab. No change in sound. Where is the trans vent tube on the 46RE? does it exit the bell housing somewhere? Other than that, the only thing I can think of is that, as you said, might be the trans line that I patched. Can't think of anything else behind the dash that would make that type of sound. At any rate, the replacement hard line should be here early next week so I'll change it out and see what happens.

Thanks again,
Mikey

 

The vent for the trans is INSIDE the bellhousing, at the top of the pump body. Once of the stupidest things I have seen. It's impossible to plumb it up higher, so, you are forever restricted in your fording depth by that vent....... It's annoying.

With vacuum disabled, I don't know of anything else inside the truck that would make that noise...... Replace the line, when it shows up, and see if anything changes.