Drivetrain Whine

[FelixOP90]

Hi all,

I bought my 99 RT10 in January and after it has been used for about 100 miles in 13 years I've now enjoyed putting 3k miles on it and just got back from the Le Mans classic with the track session there too!

I gave the car a very thorough service and new tyres when I bought it but unfortunately have developed a drive train whine. I've changed the diff oil for Motul Gear Competition 75w-140 Fully Syntheic. The old oil didn't have any glittery bits in it and there was nothing on the fill plug. The noise happens under load in any gear, 4th included. What started as a slight whine when I bought the car (and put down to the Viper rawness) has now become pronounced, especially with the windows up on the highway. It happens only when I'm on the throttle.

I'm thinking it's an issue with the differential. I'm thinking of swapping it out with a known good used unit. I can always get mine rebuilt in the winter then (possibly with different gears). Is there anything else I can check for or replace whilst I have it out? The car only has 22k miles.

Thanks in advance for any advice

 

[GTS Dean]

Rear gear whine is pretty normal. There is a lot of sheet steel and very little sound deadening - all very close to your head.

 

[FelixOP90]

I had a Corvette C4 manual with a Dana 44 and it wasn't this noisy. It's a shame there's not another viper locally I could go for a ride in to compare. I'm planning another European drive in the autumn to Spa-franchorchamps and don't want to risk a bigger problem but likewise don't want to just change things for the sake of it

 

[Steve M]

In my limited (but relevant experience), once you develop differential whine, nothing short of a rebuild will get rid of it. Many (including myself) have tried just changing the fluid, but it never works when it comes to gear whine.

My experiences:
- Had a 2002 Chevy Camaro SS I bought new off the lot. Car had gear whine. Took it to the dealer under warranty only to be told "It's a performance rear end...it's supposed to sound like that." Continued to get worse until I could no longer ignore it. Took it to a different dealer under warranty, and they agreed to rebuild it. Took them 3 attempts to finally get it right, after which it was finally quiet. I have no idea how many techs it took for them to finally find one that knew what they were doing, but my understanding is that it was rebuilt and not just outright replaced.
- Bought my 2008 Viper used with ~9,500 miles on it. During the 11 hour drive home I noted some gear whine on the highway, mostly on accel, but some on decel as well. It continued to get worse over the next few years until I took the car to the drag strip. A few passes on street tires + a few passes on drag radials pushed it to serious noise levels that forced me to replace it. Ended up swapping it with a new Gen 5 differential with 3.55 gears straight from Mopar. That one was silent.
- After some more passes at the strip on drag radials, my Gen 5 diff also developed gear noise. Steadily got worse over time to the point that I decided to attempt a rebuild myself in my garage.
- Rebuilt my original diff - equipped it with 3.73s and an OS Giken limited slip carrier. Took my time to make sure the gear setup was perfect. It was completely silent during break in. On my second pass at the drag strip, I broke one of the OS Giken output stubs which forced me to tear it down. I ultimately decided that 3.73s were too much gear for a Gen 4 unless you are willing to run a 28" diameter rear tire.
- Rebuilt my Gen 5 diff - put OEM Spicer 3.55s in it along with one of my OEM Visco Lok limited slip carriers. Again, took my time to make sure the gear setup was perfect. It was completely silent during break in, and has stayed silent. I have not taken the car back to the drag strip or run anything stickier than a regular summer performance tire (i.e., no R-compounds).

With a differential, you have to get the pinion depth, pinion bearing preload, carrier bearing preload, and backlash correct for the gears to be happy. It's a very narrow window that requires patience and determination to get it right. Hammering on it (e.g., hard launches at the drag strip) seems to mess with at least one of those variables, but I don't know exactly which. The housings are aluminum, and must distort at least some under heavy acceleration and/or wheel hop. I know for a fact that at some point during the Gen 5 production run that Dodge added some extra aluminum to the differential housing around the pinion bearings. Why? Not sure, but it was pretty easy to see once you had my old Gen 4 housing next to the Gen 5 housing, so clearly something drove them to make that change.

Your best bet would be to source a known good unit or find someone that's willing to put the sweat equity into rebuilding yours. That might be a trick since you are across the pond, but where there's a will, there's a way. I wish you the best of luck, and please keep us updated on the outcome if you do end up fixing it.