Question for those with the "Transmission Thunk/Hard shift/Clunk&#

[Steve1199]

I have a questions for all of those experiencing the "transmission thunk/clunk/hard up-shift" ect.

 

Of those who are experiencing it, how many of you have an Oil Separator installed?

 

I have been experiencing something that after my last trip to the dealer that I wanted to pass on and get opinions/experiences from the masses.

 

After my last trip to the dealer (routine oil/service), i made note of all the transmission issues i've been having since shortly after buying my truck in Nov of 14'. Issues ranging from clunky upshifts/downshifts, hard shifts, feelings of driving over rumble strips when on flat ground, clunking from rear end/transmission, moments of lack of power, and many of the other general transmission/rear end issues many complain about on here.

 

After this last trip to the dealer, a suggestion was made to me and i have had some behavior changes in the truck since then that i am not sure if they are perminent or what, but thought i would share on here for thoughts

 

Basic history of my truck:

Nov 14 - 0 miles - Bought truck, all was well

Jan 15 - ~2000 miles - started to notice clunk/thunk/bang/hard shifts

Feb 15 - ~5000 miles - Service - dealer said its transmission learning, let it learn

Apr 15 - ~10000 miles - Service - Transmission issue/clunk/think/bad shifting - greased drive shaft joints per a SB - Improvement for about a week and the grease wore off and back to old clunky

May 15 - 12500 miles - Installed RX Performance Oil/Air separator - no change to transmission/rear end issues

Jul 15 - 15000 miles - Same transmission issues - Dealer reprogrammed transmission per a SB related to another vehicle but with same/similiar transmission. was told this was a change that could not be reversed. not sure how flashing a new firmware to the TCM can not be reverted, but ok. Dealer flashed TCM with a TCM per a SB for a different vehicle. This helped for a couple week and then back to clunking, but now, the truck would occasionally (once every 1500 miles average) die on me when coming to a stop light

Sep 15 - 20000 miles - dealer service, still bad transmission issues, dealer ready to get Chevy corporate field rep involved. noted i had oil seperator installed. noted if pulled from main engine vacuum.Dealer tech mentioned that any changes made to flow of main factory vacuum could have far reaching effect. because of this, he felt that Chevy corporate would be unwilling to do much with that separator installed. removed separator per tech and re-hooked up OEM vacuum lines.

Oct 15 - 23500 miles - the truck has yet to die on idle again since removing the separator. i still have the occasional rough upshift/downshift or slight clunk from the rear, but it is a lot less than it ever was before. Overall, the truck still has some issues i feel need worked out with the transmission programming, shifting, ect, but it is a big improvement in terms of the shift points alone and how clunky/rough the transmission felt.

 

What i can't explain is the difference seemingly made by taking the oil separator off and going back to stock. The mechanic said that changing or effecting the flow if the main vacuum can have odd effects, but affecting the shift quality timing was a surprise and i'm not sure if its placebo effect or actually better.

 

How many others who have these transmission issues and all out there also have an Oil Separator?

 

I have no way to easily explain why my truck seems to be shifting better (not 100% good though) or no longer stalling, but now with that the TCM has been changed/reflashed over to some other source vehicle. all i can come up with is the possibility that the TCM reflash actually fixed something, but the oil separator was causing some issues that were masking the effects the transmission FM change had.

 

has anyone else seen this or able to add some info to what i've seen?

 

 

 

[Steve1199]

Hmmmm...........may be i got this update? http://www.gm-trucks.com/forums/topic/169997-transmission-fix-finally-for-14-15-sierra-silverado-woooot/?p=1694890

http://www.gm-trucks.com/forums/topic/177950-and-update-for-the-better-clunk-be-gone/

 

just saying my behavior changed for the better after getting the new TCM firmware and removing my oil separator (which got about 1oz per 1000 miles)

[BuyAmericanIron]

This is a new one on me and have been following the transmission issues for nearly a year. One thing you might consider is that RX Performance has been having some problems recently. From what I read a past employee copied the original design and had them built in China and was selling a sub standard product with the RX name on it. Perhaps you purchased a low quality unit made offshore and thought you were buying the real McCoy. After seeing all the crap my Elite Catch Can's capture, I can't imagine running without one. Hope you get your transmission issues repaired. It is very frustrating.

[Steve1199]

i bought mine from Jegs, so, i would hope that i got the real thing, but.............????

 

it was catching about 1oz/1000 miles or so.

 

also, with the separator on there, i had had a whining/creaking noise intermittantly coming from the driver foot well/parking brake area (roughly opposite side of firewall from brake booster pump). since i have removed my separator, i no longer heard that noise. that noise only started after maybe 1500/2000 miles of having my separator on.