Newly installed C6 shifting problem
Thread Starter
|
Senior User
Joined: Jul 2007
Posts: 403
Likes: 0
From: Story City, Iowa
Newly installed C6 shifting problem
I just got done swapping a 390/C6/NP205 into my 74 F100. The C6 doesn't want to shift into 3rd gear. It acts like it is slipping from 2nd to 3rd and the rmps go up and it doesn't do anything. What could be going on?
Little history. The C6 came from a running 74 F100 parts truck. It shifted and worked fine when installed in that truck. I pulled the drive train from that truck and put it in my good truck. While out I drained the fluid from the transmition and from the torque converter and installed new fluid.
Little history. The C6 came from a running 74 F100 parts truck. It shifted and worked fine when installed in that truck. I pulled the drive train from that truck and put it in my good truck. While out I drained the fluid from the transmition and from the torque converter and installed new fluid.
Senior User
Joined: Mar 2009
Posts: 135
Likes: 0
From: Westby, MT
Did you check the trans fluid after driving the pickup some i recently rebuilt my c6 trans and drained the torque converter and it took forever to fill both and i had to drive and fill the truck alot
Thread Starter
|
Senior User
Joined: Jul 2007
Posts: 403
Likes: 0
From: Story City, Iowa
I did. The truck has a cooler on it, so with the initial fill got 12 qts. Then after another small run on jack stands got another quart in it. Then last night I got it out and drove around the block and put another qt. in after the drive. So I was hoping 14 qts would be enough. I haven't checked it after tonights drive. I was frustrated and had to get to a meeting. So I just put it back in the garage until tomorrow night.
Elder User
Joined: Jul 2008
Posts: 522
Likes: 0
From: South Central PA
How many miles are on the C6? And how dirty was the old fluid? They say if its really dirty and old, leave it alone instead of changing it as long as it still works. Reason is that the dirt and sludge is accually working like a friction modifier and keeping the thing working. The detergents and whatnot in new atf are designed to clean that crap out, - a good thing if you keep up on your oil changes, but bad if you don't. It will then cause slipping to occur. I did this with my old Caddy. Worked great until I did an atf change and filter, then it started slipping and leaking really bad too- the cleaners cleaned the gunk off the old dry seals so then they didn't do sqat. Sold the car insted of rebuild the trans. Sounds dumb but its true.
If you were low on fluid it should slip in all gears, not just the 2nd to 3rd shift. Try some lucas additive or equivelent in it and see if it improves. Thicken it up a bit- like the dirty stuff was.
If you were low on fluid it should slip in all gears, not just the 2nd to 3rd shift. Try some lucas additive or equivelent in it and see if it improves. Thicken it up a bit- like the dirty stuff was.
Thread Starter
|
Senior User
Joined: Jul 2007
Posts: 403
Likes: 0
From: Story City, Iowa
The fluid in the tranny wasn't bad. The engine and tranny only had about 20-25k on a rebuild (reason I bought the parts truck). I have heard of the changing of the fluid thing. I will get some additive and try that.
The thing is, it shifts fine from 1st to 2nd, reverse is fine, it's just 2nd to 3rd. It never really acts like it engages. Does the vacuum have anything to do with shifting. Just wondering if I had the vaccum lines screwed up, or if the vacuum modual on the tranny is bad.
Double check me, the vacuum lines, the modual vacuum line goes to the vacuum tree on the back of the engine. The other line goes to the back/bottom side of the carb. Let me know if those are right. It maybe I just have the lines in the wrong spot.
The thing is, it shifts fine from 1st to 2nd, reverse is fine, it's just 2nd to 3rd. It never really acts like it engages. Does the vacuum have anything to do with shifting. Just wondering if I had the vaccum lines screwed up, or if the vacuum modual on the tranny is bad.
Double check me, the vacuum lines, the modual vacuum line goes to the vacuum tree on the back of the engine. The other line goes to the back/bottom side of the carb. Let me know if those are right. It maybe I just have the lines in the wrong spot.
