: Caution those with Revshift DS couplers



OneFast V
04-06-13, 11:54 PM
This morning I hopped in the car with some friends to grab breakfast and head down the street. As soon as I hit 25+ mph I get this HORRIBLE shaking and vibration throughout the car. I immediately turn around and park the car. jack it up and find out that every single DS bolt has come loose, one was missing and one bushing had fallen out! It turns on that the factory tension nuts are a one time use part and not meant for re-use. this almost became catastrophic! I'd recommend everybody replace their tension nuts if they re-used the OEM hardware and I would recommend Revshift either make it VERY clear not to re-use these nuts or include a new set with the DS coupler. So now my coupler bushings are trashed so hopefully they will warranty it.

FuzzyLogic
04-07-13, 12:40 AM
This morning I hopped in the car with some friends to grab breakfast and head down the street. As soon as I hit 25+ mph I get this HORRIBLE shaking and vibration throughout the car. I immediately turn around and park the car. jack it up and find out that every single DS bolt has come loose, one was missing and one bushing had fallen out! It turns on that the factory tension nuts are a one time use part and not meant for re-use. this almost became catastrophic! I'd recommend everybody replace their tension nuts if they re-used the OEM hardware and I would recommend Revshift either make it VERY clear not to re-use these nuts or include a new set with the DS coupler. So now my coupler bushings are trashed so hopefully they will warranty it.

I've removed and reinstalled the stock coupler bolts at least 10 times with no problems. I wonder whether the Revshift coupler put extra stress on the bolts.

OneFast V
04-07-13, 01:08 AM
I've removed and reinstalled the stock coupler bolts at least 10 times with no problems. I wonder whether the Revshift coupler put extra stress on the bolts.

Not sure what duration you are going between pulling them on and off but this happened over the course of close to 10k miles. I have not touched it since I installed it.

PISNUOFF
04-07-13, 09:18 AM
I've removed coupler bolts and nuts at least a dozen times without replacing or using Loctite. There has been times with longer than 10k miles between changes. They are not one time use bolts because there isn't any stretching and they are not clinch nuts. Just replace them and use Loctite.

soulja
04-07-13, 09:48 AM
Loctite^^^^

robojesus
04-07-13, 12:25 PM
this has actually happened to me before too, but with the stock coupler. advance auto has the grade 10.9 bolts you need to replace.

Bacon V
04-07-13, 12:40 PM
This is a lot of speculation, but its probably more likely that the coupler failed due to driveline misalignment than it did because of a fastener issue. As others have stated, these are not single use nuts or a "locking" specific nut. The clinch feature in the nut is there to prevent the nut from loosening during vibration - the torque is what secures the nut.

If you had a worn tranny mount, for instance, it would cause a droop in the driveline - the same would happen with a sagging carrier bearing. If this happens its putting a bend at the flex coupler which causes alternating loads on the poly bushings. Lets assume that the coupler is ~5" in diameter and has a circumference of ~16". If a hard accel caused 5 degrees of driveline rotation (guessing) then you would have 16"*(5/360)deg = ~.2" of stretch. In the stock coupler, this deflection is spread through the entire disc. In the revshift, that same deflection has to be spread between the 6 poly bushings that are much smaller in total "circumference" (adding the diameters as if it were a solid feature). In effect, this causes a much larger percentage stretch of the material. Im assuming the revshift poly bushings are harder material and more prone to fatigue or tearing failure. In a perfect driveline they are probably great, but it seems that under slightly worn conditions they blow apart. This is not the first time ive heard of this failure mode.

Sorry if this got long and didnt make any sense...

OneFast V
04-07-13, 01:03 PM
straight from mcmaster-carr:
http://www.mcmaster.com/#hex-locknuts/=m7vy2v
Distorted-Thread Hex Locknuts
Also known as all-metal and Stover locknuts, these one-piece nuts feature distorted threads that create a vibration-resistant friction fit—so the nuts stay put. Not reusable.


Anyways I have the CS tranny mount and CS diff mount and block so nothing else in the driveline could be sagging other than driveshaft itself. I for one will not be taking the chance of reusing these nuts.

Bacon V
04-07-13, 01:31 PM
Use whatever nuts you want, but I guarantee you that GM does not use overpriced McMaster nuts. If I remember correctly (from when I removed and reinstalled the same hardware), they came out with green thread locker on the threads. Perhaps you should have used some when you put them back in.

lollygagger8
04-08-13, 09:20 AM
I too had removed my stock driveshaft/coupler probably in the teens as far as times and never had any problems. I also made sure I put the DS and coupler on the same way everytime (by marking it) to avoid vibes in the future.