CrossedPistols

My 2001 auto coupe doesn't want to shift into third at low RPMs. If I accelerate hard it will go to redline without shifting. When I let off on the throttle it will shift into third. If I accelerate slowly it will shift but not until it gets to about 4k. It has power in 2nd, it just wont go into 3rd like it should.

Am I losing a clutch and facing a costly rebuild? Or, please, could it be something else?

Bill Curlee

The VERY FIRST thing that you have to do is see if you have any DTCs set for the transmission. Enter the DTC reading routine and list ALL the DTCs that you have. Especially the P series DTCs.

My guess is that you have a shift solenoid issue and it could be a blown fuse or bad solenoid. List the DTCs and that will get us started on getting this resolved.

BC

Route99

First: Have you done any work to the trans or had anyone else do any trans maintenance? Have you had a recent tune performed that could have affected the shift points/pressure?

Second: Have you checked for DIC codes? If the problem is electrical (solenoid) it could reflect there.

Third: Have you checked your trans fluid level? A possible inexpensive fix attempt would be to change the fluid and filter. Long ago, there were issues that the filter could have gaps that would keep it from maintaining vacuum which would then reduce the fluid pressure in the transmission.

If the transmission fluid level is full, does it smell burned? This could represent something overheating in the trans; quite possibly the 3-4 clutch pack.

Hopefully it is just low fluid or even the servo which is still a cheap fix. If not, you may be right about a rebuild. Ouch.

Oops: Just saw Bill Curlee beat me to the punch about the solenoid.

CrossedPistols

No codes. Just LDCM U1064 loss of coms with my door.

CrossedPistols

I'll get it to the lift and check the fluid. I might as well change it while it's in the air. I changed it when I got the car at 115kmiles. It's at 154k now. I was going to do it at 165k (50k between changes) but if it could be an inexpensive fix it's worth a try now. Thanks

Bill Curlee

When was the last time you check the trans fluid level?? Do you know how to do it properly?

Bill

CrossedPistols

The oil is full and a beautiful color. No smell I could discern.

pjensen

So you had the engine running (and the transmission in park) when checking the fluid level?

The only way to see if is full is to try to add more and see if it overflows.

ncali

where do you check the trans fluid level in a c-5

Bill Curlee

WARNING!!! REFERENCE THE SERVICE MANUAL for the exact procedure . If you do the check/fill procedure wrong, you could damage the trans and or BURN your self if the oil is hot!.

Drivers side of the trans on the pan. ENGINE MUST BE RUNNING when you remove the fill plug and or add fluid!!!!!!!!!!!

ncali

thank you for the reply. I have made a friday appt at the trans shop so they can change oil , filter

BigGun

Make sure they are aware of the correct fill procedure. Sadly some shops are not. Some trans shops have never worked on a C5. The service manual will have you drop the pan and change the filter along with the fluid.

Bill Curlee

Man,,,,,,,,,,,,,,, You are thinking exactly like me... I SECOND that recommendation.

Even though they are a "TRANSMISSION SHOP" they might not be familiar with the CORRECT C5/C6 fill procedure. If it were me,,, for piece of mind, I would ASK.

Let us know how it turns out.

Bill

vipmiller803

If your fluid is not low, not leaking, and not burnt, you may be throwing away maintenance budget replacing it now, considering a rebuild is a possible need.
I'd opt for the shop to diagnose the issue rather than just throwing fluid in, potentially causing more harm than good. A scan tool should tell you the commanded gear. If third is not commanded until 4k rpm, the trans has nothing to do with this problem and you would have to look at what's causing the pcm to make erroneous commands.
If the command is simply not being followed, then something in the wiring or the trans is the issue, and you could take your diagnosis from there. A solenoid problem can be diagnosed without opening up the trans.

ncali

any thoughts on synthetic trans fluid?

Bill Curlee

Switching to a synthetic fluid this late in the game is NOT going to make ANY difference. IF the fluid is not low or burnt, I would have to agree with VIPMILLER 803 in that you are wasting time and money. If its burnt, then you need a rebuild.

Another point to PONDER.. If the trans is not shifting correctly,, it SHOULD be throwing DTCs. If NOT, like VIPMILLER803 stated, you need to track that issue down FIRST!

BigGun

Vipmiller803 and Bill make excellent points. A fluid change at this point would be a waste of money.

CrossedPistols

That's what I thought. Since it's not throwing codes on the DIC I was baffled. Anyone in the NOVA or DC area know a reputable mechanic? I don't want to be taken to the cleaners by someone who sells me something I don't need.

Bluefire

I just wanted to add that the FSM also states that the transmission fluid temp MUST be between 86 degrees F and 122 degrees F to get a proper level reading. I read mine when fluid was quite warm and it was full. I then waited until the fluid was at the correct temp and I found that I was 22 oz. low!!!!

kh400

direct clutches are burned up.