Harsh down shifts from 6spd

[Centex14]

Truck has a 115k miles on it.  No leaks or drips anywhere.  Problem is that it downshifts harsh.  And by harsh I mean I'm waiting for a u-joint to snap when it does because it's so violent.  When I'm coming to a stop the 2-1 shift jolts the truck.  If I'm cruising around 55mph and stand on it it bangs into gear and takes off.  I plan on dropping the pan and changing the filter and adding new fluid but just haven't had the time in the 3 days I've owned it.  It may be because I pulled the fuses and am going through the relearn procedure on it or it could be I'm paranoid.  Otherwise it runs great.  Upshifting is fine and quick.  Just the down shifts seem harsh and violent.  Anyone else experienced this?  I've tried searching but I must not be entering the correct information.

[Jonty711]

If you’re not sure of the history of the truck, be careful swapping fluid. You might do more harm than good.

[Centex14]

That’s my other concern. Ruined one trans on an old truck that way.


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[Deadpoollane]

Is it a v8? If so watch to see if it happens when it goes into v4 mode.

I know my old truck had a hard tug when it went in to the v4 on higher gears


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[silveradosid]

have it scanned for codes and see if there any pending codes

[Doublebase]

I don't think I'd be too concerned doing a tranny service at 115,000 miles. That's not excessively high mileage to do a service like that. If it were 215,000 and the fluid never was changed? Then I might worry but not at 115,000.

[Centex14]

I'm getting the pan dropped and filter changed on Wednesday.  Fluid looks nasty.  I'll re-evaluate from there on whether I do a full flush in a month or so or just leave it be.  From the reading I've been doing the past week, sounds like it's not unusual for the 6spd to just be a goofy shifter until it gets tuned.  Also doesn't seem unusual for flushes to occurr at 100k mile intervals either.

[Centex14]

Dug through the service records and one of them says transmission fluid change at 56k miles. So now I’m not near as concerned with changing the fluid out.


2014 z71 LTZ
Volant Intake
Borla Exhaust

[Silverado-Hareek]

A pan drop fluid change is fine at that mileage, even without prior service.  It's the full transmission flush you have to worry about.  Even so, those have become less of a concern with modern flushing systems.  In particular, BG has a good flushing system that utilizes the transmission's own fluid pump to cycle out the old fluid and replace it with new.  The best way to describe the process is it's like a blood transfusion.  The pump and transmission work as if you were out driving around, except instead of cycling the existing fluid in a loop, the old fluid is pumped out as new fresh fluid is pumped in.  The BG machine has a window so you can monitor the color of fluid leaving the transmission.  Initially the fluid leaving the transmission is dirty and looks black.  As the service process plays out, the color of the fluid in the viewing glass gets progressively lighter until you finally see nothing but fresh new light red color fluid cycling out of the transmission.  That's when the process is complete.  Since this system utilizes the transmission's own pump, there is no pressurized forcing of fluid through the transmission by outside sources.

 

 

[Retired Bob]

For a 'basic' explanation of why not to change transmission fluid:

 

[Centex14]

Ended up getting a full flush since it’s been done once before. They used the BG machine so no added pressure. Can’t tell any difference but at least it’s clean now.

 

And I’ve ruined one transmission just doing a pan drop so I’m well aware of the dangers and that trans had services done regularly and then did a pan drop on another that hadn’t been changed in 220k miles and it held fine so who knows. Given my family’s history with changing trans fluid, it’s a crap shoot either way.

 

 

2014 z71 LTZ

Volant Intake

Borla Exhaust

Diablo