I have a 2007 mn6 z51. it has 1200 miles on it. here is my problem, when I shift from 2nd to 3rd it feels like it is grinding or somethnig. it feels like the clutch is not inguaged the whole way. Has anyone else experienced this problem.

 

Yep, I've noticed it as well, I even somehow missed 3rd a couple times for NO reason since I shift the same way all the time. After a post on these boards I was told to palm 3rd into gear and just push up, that was ok but after a little I went back to the grip method. Oddly though for the past couple weeks 2nd-3rd shift has been better, perhaps it fixed itself?! Or perhaps with some more miles the trans as "broke-in" better. Right now I have 1900 miles.

 

That is typical behavior for Tremec MN6 (MM6 or MZ6) when the fluid is cold...it's the synchos trying to line things up inside for the next gear.

The slight vibration/noise through the shifter is un-nerving at first, but is not a serious problem unless you bang shifts with cold fluid to try and fix it. You are probably just noticing it now because the outside temps are dropping and the fluid in the tranny is colder when you start out. Make gentle shifts until your fluid temps come up to normal operating levels; I usually watch the engine oil temperature.

If the condition persists after you warm up the transmission fluid, then it's a tranny problem...shouldn't do it.

Edit: Another possibility is that the clutch really IS NOT disengaging completely, but I would expect rough shifting in ALL gears if it were the clutch. Do a search for threads about changing the clutch fluid using the "turkey baster" method. I'm doubtful that it's clutch fluid deterioation with that low mileage, but if it's not low tranny fluid temperature, then the bad clutch fluid possibility has to be eliminated. On 2005s, there are mechanical reasons why clutches on some VINs may not work properly, but that problem was fixed in 2005.

 

I have also noticed increased shift effort since the weather has turned cold. However, even when the outside temp was warm and the car at operating temp, the shifting was not as crisp as I would like. I have heard that changing to a synthetic trans fluid will help. While installing the CAGS eliminator today, I noticed the trans fill plug but didn't see any drain plug. Did I miss it or does the fluid have to be sucked out with a pump? Also, what is the best recommended synthetic fluid to use? The label on the trans says Dexron III.

 

You don't say how many miles you have on your car, but you should expect this rough shifting 1-2 and 2-3 to improve as you put more miles on and transmission parts wear in. That may be part of my car's improvement from last winter; it now has 3700 miles. I'm not sure if this ever goes completely away with cold fluid...some cars are reported to continue this trait with 5K miles or more on them.

From what others say, you will probably get the most improvement with Royal Purple Synchromax, but you will likely be out from under the GM warranty umbrella when you use it. Any fluid, synthetic or not, that meets GM's Specification H will keep your transmission under warranty. Read the label on any candidate fluid for meeting Spec H if you want to keep your transmission under warranty. I did a little research on this subject thinking I might have to change my fluid, and Mobil 1 synthetic Dexron ATF meets Spec H...that would be my choice if I have to change. Experience of others that have changed to the Mobil 1 report some improvement, but maybe not as much as others using the Synchromax.

Edit: There IS a dedicated drain plug. On C5s, the drain on the Z51 (MZ6) was the fluid temperature sensor, but on C6s there is a separate drain plug in spite of the service manual's incorrect info. Do a search; it seems like someone did a "how-to" thread on transmission fluid change.

 

Thanks for the quick reply. Yes, my car has only 1350 miles and I hope it improves with more miles. I did not see any drain plug but did notice the temp sensor which would also work as a drain when removed. Note; I have a 2007 coupe with the Z51 trans. Thanks again.

 

Cold definitely makes a difference. Mine is notchy as hell until it warms up, once in a great while hard to get into reverse. Once warmed up a bit, it's fine. However, 2-3 has been noted by the car mags as being cranky. I rely on the spring load 3-4 slot to align my shifts--let the spring bring it to center, and then up or down is a straight line. 2600 miles on the car, so still not really broken in completely. Don't see it as a problem as long as op temp makes it go away.

 

Thanks for all the info. I only have 1200 miles on it. Maybe I will wait another couple thousands miles and if it is still there I will take it back to the dealer. thanks

 

It's not going to improve with age. It will improve slightly if you change it to high quality synthetic. I've always had good results with the Amsoil auto trans fluid. It's the right Dex spec.

What you will notice is it starts to shift smoother sooner. With good synthetic it may only be that slight grindy feel the first couple of shifts, then real smooth within a minute or so of driving. Non synythetic it make take twice that long or 10 or 15 minutes or so of driving before it smooths out.

The other thing I've noticed that helps is as your first rolling down your driveway, just a couple miles an hour. Row the shifter through 1st to 2nd to 3rd. Spins up the gears, gets things lubed, and your not moving fast enough to grind them. I've found doing this makes the first couple of real 1 to 2 shifts and 2 to 3 a little smoother. If you just take right off cold with non syn, those first couple shifts can be pretty grindy. Nature of the beast, but you can improve it a bit with synthetic trans fluid.

 

[QUOTE=JmpnJckFlsh]That is typical behavior for Tremec MN6 (MM6 or MZ6) when the fluid is cold...it's the synchos trying to line things up inside for the next gear.

The slight vibration/noise through the shifter is un-nerving at first, but is not a serious problem unless you bang shifts with cold fluid to try and fix it. You are probably just noticing it now because the outside temps are dropping and the fluid in the tranny is colder when you start out. Make gentle shifts until your fluid temps come up to normal operating levels; I usually watch the engine oil temperature.

QUOTE]

Un-nerving is an understatement Even with light weight shifts, I'll grind at least once on the 2-3 then it goes away. Temp's don't seem to be an issue.

 

Many different opinions on this question...

The AMSOIL ATF meets the GM specifications for your car and is what I've been using in my 02 Z06 on the track for several seasons now without any transmission failures.

 

Severity of this issue varies from transmission to transmission...your result may not be the same as others. I don't notice this balky shifting problem when the temps are above about 65-70 deg.

If you always have this grinding on the first shift or two, then change to a synthetic fluid, or try Michrider's suggestion to pre-lube the transmission before driving.

 

[QUOTE=JmpnJckFlsh;1557842143]You don't say how many miles you have on your car, but you should expect this rough shifting 1-2 and 2-3 to improve as you put more miles on and transmission parts wear in. That may be part of my car's improvement from last winter; it now has 3700 miles. I'm not sure if this ever goes completely away with cold fluid...some cars are reported to continue this trait with 5K miles or more on them.

From what others say, you will probably get the most improvement with Royal Purple Synchromax, but you will likely be out from under the GM warranty umbrella when you use it. Any fluid, synthetic or not, that meets GM's Specification H will keep your transmission under warranty. Read the label on any candidate fluid for meeting Spec H if you want to keep your transmission under warranty. I did a little research on this subject thinking I might have to change my fluid, and Mobil 1 synthetic Dexron ATF meets Spec H...that would be my choice if I have to change. Experience of others that have changed to the Mobil 1 report some improvement, but maybe not as much as others using the Synchromax.

Jmpnjck,

Are there different weight oils or do I need to just look for the Mobil 1 synthetic Dexron ATF? What are others using to help with the up shifts?

Thanks

 

Is there a drain plug on the trans?

 

While fluid viscosity and temperatures may affect the smoothness of the shift I believe what the original poster is refering to is the angle in which we must shift from 2nd to 3rd. If you search you will see that many 6M owners are having the same trouble. I do not believe this is a fluid problem. You just have to get used to the angle in which you have to go from 2nd-3rd, your hand position, and the amount of pressure to apply. There are several posts with advice on making the 2nd-3rd shift better. Just keep practicing.

 

I haven't changed my transmission fluid yet. I'm saying that if I DO change, it will be to Mobil 1 synthetic ATF.

I was just holding a bottle of Mobil 1 synthetic ATF in my hand yesterday; it will say that it's for vehicles using Dexron/Mercon fluids, and on the front of the bottle, it clearly says that it meets Specification H...that, with the Mobil 1 label, is all you need to know

Even with the colder temperatures this year, it seems to me that my transmission is having less of a problem this year than last, but it could be because I am aware of the condition and make the first few 1-2, 2-3 shifts easy. At this point, I will probably NOT go to the trouble to change the fluid.

 

Possibly. But, when posters complain of missing the 2-3 shift because they're forcing the shift, the typical result is not gear "grinding" as I understand it...the shift lever just goes forward, apparently in gear, but the transmission stays in neutrel. At least that's what I read here...I can't say from experience because it hasn't happened to me.

However, you could be right about his question...in that case, I apologize for taking this discussion down the wrong road. If the OP IS trying to force the shift, he needs to quit trying to push the shifter to right as he shifts forward. If he can't find the 3 gate any other way, he should just push the shifter forward with his palm...the shifter is spring loaded to the 3-4 gates; it will automatically go into third gear without side force.

 

Put a Hurst shifter in it and you wiill never miss 3rd rear again. I have only about 1500 miles on my 07 now,but change to a hurst at 900 miles. Best mod I have done.

 

yes the drag plug is on the tranny. if you do change the fluid and has z51, make sure you run the engine a little bit while up in on the jack then see if you can refill some more due to the tranny oil pump.