Skip to main content ↑ ↓
Topic: Cat 3208 / ORED torque converter noise between 3rd and 4th gear? (Read 488 times) previous topic - next topic

Cat 3208 / ORED torque converter noise between 3rd and 4th gear?

Another question for you guys: my Cat 3028 is pretty quiet and a smooth runner. The only exception is when in third gear between 2400 rpm and 2500 rpm (right before it shifts into 4th). At that time there is a loud, for lack of better term, harmonic imbalance that comes from the back. It sounds like a really loud fan humming and right before the shift into 4th, it lets off and briefly re-engages again before going silent... it sounds like a clutch maybe.

The radiator fan is direct drive, so if it were that I would expect it to exhibit the same behavior in 4th gear but it does not. Could it be the torque converter? Drive shaft needs rebalancing? Any one else with a Cat 3208/Allison combo experience this? There's no noticeable change in performance...shifting remains smooth through out; it's just noise.

Re: Cat 3208 / ORED torque converter noise between 3rd and 4th gear?

Reply #1 –
Do you have the side radiator? If so the transmission has a different sound when shifting than the 250 hp rear radiator.

Re: Cat 3208 / ORED torque converter noise between 3rd and 4th gear?

Reply #2 –
 
Quote from: red tractor –
Do you have the side radiator? If so the transmission has a different sound when shifting than the 250 hp rear radiator.
I have the rear radiator

Re: Cat 3208 / ORED torque converter noise between 3rd and 4th gear?

Reply #3 –
Mine only hums a bit at 68 mph. Diff whine .
Might change trans and diff oils ?

Re: Cat 3208 / ORED torque converter noise between 3rd and 4th gear?

Reply #4 –
Quote from: Protech Racing –
Mine only hums a bit at 68 mph. Diff whine .
Might change trans and diff oils ?
Yea all new fluids are going in before our first trip. Maybe that'll do it.  Need to get the U320 sold before I really start digging in though

Re: Cat 3208 / ORED torque converter noise between 3rd and 4th gear?

Reply #5 –
Quote from: Elliott –
The only exception is when in third gear between 2400 rpm and 2500 rpm (right before it shifts into 4th). At that time there is a loud, for lack of better term, harmonic imbalance that comes from the back. It sounds like a really loud fan humming and right before the shift into 4th, it lets off and briefly re-engages again before going silent.

Elliott, you really need to stop worrying about this.  All you have so far is a noise you heard.  Just what do you think a clutch sounds like?  If the tachometer didn't start heading for the sky, it's not a clutch.  If you're worried about the clutch, lift off during the shift and give the clutch(es) time to fully engage.  I have about 10 years on a motorcycle clutch that was slipping because of the wrong lubricant being used. BTDT.

Re: Cat 3208 / ORED torque converter noise between 3rd and 4th gear?

Reply #6 –
Quote from: Protech Racing –
Mine only hums a bit at 68 mph. Diff whine .
Might change trans and diff oils ?
Changed both. Transmission oil was nice and clean, diff oil was sludgy as hell and about a gallon low. Not even a fleck of metal on the magnet though, thankfully. Hoping it was indeed the diff and this clears it up because everything else under there looks tight and relatively well cared for. We head to Vegas at the end of the month and I'll know then one way or another.