: Transmission issue - intermittant grinding when shifting into 1st gear



DDS rollin a CTS
10-25-11, 12:53 PM
About a week ago I started noticing that occasionally when shifting into 1st gear either when stopped, or expecially if still slowly moving (2-5mph), I would hear and feel a grinding sound comming from the transmission. It also seemed to be getting harder to shift into all gears. I talked to a number of people and the unanimous diagnosis I got was bad transmission fluid. This morning I took the car to my mechanic and had the fluid changed with Dextron VI automatic transmission fluid (yes I know it says Dex III on the transmission housing, but the bulletin he had from GM, and the tranny guy at the local dealership both said Dex VI superseeds Dex III). He said the fluid definately needed changing because what came out was dark brown instead of red like its supposed to be. Shifts are now much smoother in all gears...except for 1st, where I still experience the grinding. It doesnt happen every time I shift into 1st, but over the last week since it started happening its done it more and more often. At this point it grinds more often than it doesnt. Its driving me so crazy that I'm no longer even using 1st, and starting in 2nd instead. My mechanic thinks maybe a linkage needs adjusting, but he's going to have to do more research first to find out. What do you guys think? Should I just take it to the dealership and let them look at it? As some additional background I do autocross this car so its under more stress than average, but I specifically avoid hard starts due to the history of these cars and their diffs. Thanks!!!

falke401
10-25-11, 01:11 PM
Have you changed your clutch fluid? That might help, but I wouldn't count on it. It could be the synchros going out in first gear.

If you need to buy some time between getting it fixed, I would just start in second gear.

mstrjon32
10-25-11, 01:12 PM
I wouldn't use Dex VI in the transmission. Dex VI supersedes Dex III in *automatic* transmissions, and as I recall there is some incompatibility with Dex VI and one of the metals used in our transmissions (something involving Brass, maybe?...someone else might be able to chime in).

If all of your other gears are engaging smoothly now my guess is that the synchros on 1st are worn, but using a high-quality fluid like Amsoil might improve things. A fluid change for the clutch certainly isn't going to do any harm, either...

Houdini
10-25-11, 02:33 PM
+1 on full clutch fluid replace and bleed. I don't think the newer dex fluid will hurt your trans... I believe there was an issue with older model t56 trans but not in the V (it is updated).

DDS rollin a CTS
10-25-11, 11:37 PM
I certainly hope theres no issue with using dex VI because it was the tranny guy at the cadillac dealership who told me specifically to use dex VI. I have changed and added fluid to the clutch reservoir but not changed the fluid in its entirety. Also my mechanic said it doesnt feel like worn synchros, but I dont know what that feels like as this is my first manual transmission. I have an appointment with the dealership tomorrow, I will let them take a look and see if they recommend anything else.

What all is involved in replacing the synchros? I've been thinking about upgrading the clutch and flywheel whenever major service is needed on the transmission, would this be a good time to go ahead and do that?

falke401
10-26-11, 09:13 AM
I do not know the procedure for replacing synchros, but while the transmission is out, it is a good time to replace the clutch, flywheel, slave cyl, ect.

DDS rollin a CTS
10-26-11, 11:59 AM
Update - I took the car to the dealer this morning. After an hour of poking, prodding, and test driving they determined the problem is internal, but they don't know what yet. They're going to drop the tranny to see what's going on. I do have powertrain warranty but they said it depends on what's wrong on whether or not it's covered. I inquired about replacing the clutch and flywheel, and while he said thats something he's seen done, and they could even do it for me while they had it apart, it would definately void the remainder of the waranty from the flywheel back. I chose this point to go ahead and mention that my diff has been whining and asked them to investigate that further as well. I guess if they go ahead and replace the diff under waranty, then I wont be so worried about it and go ahead and do the clutch and flywheel myself.

mstrjon32
10-26-11, 12:08 PM
I certainly hope theres no issue with using dex VI because it was the tranny guy at the cadillac dealership who told me specifically to use dex VI.

Here's some banter on gminsidenews.com about it: http://www.gminsidenews.com/forums/f53/dexron-vi-6-a-64757/index4.html (I hope linking to other forums is OK)
And here's a picture from bobistheoilguy.com showing the back of the bottle that states that it should NOT be used in manual transmissions: http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1477775

Make up your own mind, but I would drain it and replace it with a fluid specifically intended for use in your box. Might even fix your shifting problems...

CadzillaTN
10-26-11, 09:58 PM
DDS how many miles do you have?

DDS rollin a CTS
10-27-11, 12:55 PM
Update - So I talked to the service advisor last night. Turns out the synchros for 1 and 2 are toast. Also the clutch slave cylinder was leaking, and there was one other thing that I dont remember. Anyways, theyre replacing the synchros and the clutch, all under waranty. Fortunately or unfortunately, they determined that my diff is probably a gen 1, but not in need of replacement at this time. I hope to have the car back Monday or Tuesday. Oh well, at least they gave me a Traverse to drive and not that shitty HHR they were trying to stuff me into.

CadzillaTN - My V has 44k miles, 14k of which are mine put on since March of this year.

CadzillaTN
10-27-11, 02:18 PM
You are golden then, plenty of time to get that diff changed!

Are they doing the flywheel too?

I had issues with 1st until they replaced the whole gear, now it's fine.

I will say that I never really attempt to get into 1st at any decel speed.., I use second unless I dead stop. Even then it's second unless the incline is more than 20 degrees.

JimmyH
10-27-11, 02:20 PM
Update - So I talked to the service advisor last night. Turns out the synchros for 1 and 2 are toast.

That's what you get for flying through the cones so fast :D

DDS rollin a CTS
10-27-11, 04:33 PM
You are golden then, plenty of time to get that diff changed!

Are they doing the flywheel too?

I had issues with 1st until they replaced the whole gear, now it's fine.

I will say that I never really attempt to get into 1st at any decel speed.., I use second unless I dead stop. Even then it's second unless the incline is more than 20 degrees.

I dont think theyre doing the flywheel too. I use 1st mostly just for deadstarts too, and second if i'm doing a "rolling stop".


That's what you get for flying through the cones so fast :D

Bah, youre just jealous! ;)

Houdini
10-27-11, 04:41 PM
Fortunately or unfortunately, they determined that my diff is probably a gen 1, but not in need of replacement at this time.

You have an 07 V so it wouldn't be a gen 1 diff. Gen 3 diff was stock for 06/07 Vs.

JimmyH
10-27-11, 05:49 PM
gen1 was 04/05
gen2 was 06/07
gen3 started getting used sometime in mar 08
I am not sure where gen4 came in.

CadzillaTN
10-27-11, 06:32 PM
It didn't. gen4s are most likely repackaged gen3s. That's my theory anyway.

JimmyH
10-27-11, 10:28 PM
Yeah, I have never seen any evidence of any difference besides part numbers.

DDS rollin a CTS
11-03-11, 04:22 PM
Well I got my car back today. They replaced 1 & 2 synchros, inner and outer block rings, replaced clutch assembly, and replaced actuator assembly. Grand total had I not had waranty: $2395.91, and that doesnt include the free rental for 6 days. Looks like I'll be looking in to an extended waranty again, just need one repair like this for it to pay for itself. Anyways the verdict? Awsome. It shifts better now than it ever has in the time I've owned it. The other thing I noticed, before even with the "pissnuoff short shifter" it had more side to side slop in the shifter than jenna jamesons you know what after a long day at work. Now it has a very firm direct feel with very little play.

This all leaves me with one question, is there any sort of "break in procedure" for the new clutch or synchros? I asked the service advisor and he just said avoid powershifting for a while but said everything else was fine. What do you guys think?