Transmission issues
Thread Starter
|
4th Gear
Joined: Dec 2022
Posts: 4
Likes: 0
From: Las Cruces NM
Transmission issues
I inherited my dad's 1980 ford f350, truck has a 400m engine and a C6 transmission. That being said, I am having shifting issues with the transmission as well as a wierd ping when I put the truck into park. The transmission will shift into first and second and won't go past that. I replaced the carburetor with a Edelbrock AVS2 and am not sure if I connected the vacuum lines correctly. Any help would be appreciated!
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
Welcome to FTE
Let start with the ATF fluid level.
Up to temp in park is the level in the safe zone?
If not add or remove some to get it there.
Now under the truck under the transmission to the back you should see a vacuum line going to a valve.
First pull the hose off the valve do you see any ATF? If so the valve needs to be replaced other wise put the hose back on.
Did it fit snug to the valve & metal line? It needs to.
Follow the metal line up the back of the motor and it should go to manifold vacuum. A port that has vacuum all the time.
If that is all good it gets a little deeper and someone that knows a little more on autos will have to step up.
Dave ----
Let start with the ATF fluid level.
Up to temp in park is the level in the safe zone?
If not add or remove some to get it there.
Now under the truck under the transmission to the back you should see a vacuum line going to a valve.
First pull the hose off the valve do you see any ATF? If so the valve needs to be replaced other wise put the hose back on.
Did it fit snug to the valve & metal line? It needs to.
Follow the metal line up the back of the motor and it should go to manifold vacuum. A port that has vacuum all the time.
If that is all good it gets a little deeper and someone that knows a little more on autos will have to step up.
Dave ----
Moderator
Joined: Jan 2001
Posts: 56,949
Likes: 2,718
From: Virginia
Start the engine and with it idling get under the truck on the passenger side and pull that vacuum line off that the previous Dave was talking about on the transmission. Does it suck on your finger when you pull the line off? If not, you don't have the vacuum lines hooked up correctly like you thought.
Thread Starter
|
4th Gear
Joined: Dec 2022
Posts: 4
Likes: 0
From: Las Cruces NM
Welcome to FTE
Let start with the ATF fluid level.
Up to temp in park is the level in the safe zone?
If not add or remove some to get it there.
Now under the truck under the transmission to the back you should see a vacuum line going to a valve.
First pull the hose off the valve do you see any ATF? If so the valve needs to be replaced other wise put the hose back on.
Did it fit snug to the valve & metal line? It needs to.
Follow the metal line up the back of the motor and it should go to manifold vacuum. A port that has vacuum all the time.
If that is all good it gets a little deeper and someone that knows a little more on autos will have to step up.
Dave ----
Let start with the ATF fluid level.
Up to temp in park is the level in the safe zone?
If not add or remove some to get it there.
Now under the truck under the transmission to the back you should see a vacuum line going to a valve.
First pull the hose off the valve do you see any ATF? If so the valve needs to be replaced other wise put the hose back on.
Did it fit snug to the valve & metal line? It needs to.
Follow the metal line up the back of the motor and it should go to manifold vacuum. A port that has vacuum all the time.
If that is all good it gets a little deeper and someone that knows a little more on autos will have to step up.
Dave ----
Ok dave so i checked the ATF fluid and i believe that its at an ok level, its hard to tell on that particular dipstick. As to the valve i pulled the hose and there was no ATF fluid on the hose and the hose was pretty tight as well. i can get the transmission to shift into reverse, first second and third but nothing past that. I do have the vacuum hose line hooked up to the front drivers side Vacuum port on my edlebrock AVS2 Carb.
Thread Starter
|
4th Gear
Joined: Dec 2022
Posts: 4
Likes: 0
From: Las Cruces NM
Trending Topics
Cargo Master
Joined: Aug 2007
Posts: 2,558
Likes: 69
From: New Zealand
If you can feel 2x up-shifts (1-2 & 2-3), that's it......no 4th gear
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Hotshot
Joined: Jun 2015
Posts: 12,767
Likes: 2,420
Thread Starter
|
4th Gear
Joined: Dec 2022
Posts: 4
Likes: 0
From: Las Cruces NM
So after paying real close attention to the shift points i believe that the transmission gets stuck in second gear. The shifts are pretty rough from gear to gear then the transmission hangs up in second gear. I tried stomping on the pedal to see if i can get it to shift and nothing happens. I bought a vacuum gauge and tested the line going into the vacuum valve on the transmission, at idle im running 20-30. I dont know if that is enough vacuum. I dont have any fluid running out of the valve however im considering changing the valve anyway as the truck sat for a while. I did check and its not burnt, however it was a little low so i refilled which made no difference.
Moderator
Joined: Jan 2001
Posts: 56,949
Likes: 2,718
From: Virginia
The only other thing to check, is to make sure the kickdown is not hung up and activated all the time. The gear selector lever and the kickdown lever both come out of the same place on the side of the trans. The kickdown lever will have a linkage going up to the carb. Make sure it's free and springs back to it's home position. If you are unsure, just take it loose down at the trans and make sure the lever goes back to home. I have had the kickdown get stuck in the on position and that messed the shifting up on my transmission.
Cargo Master
Joined: Aug 2007
Posts: 2,558
Likes: 69
From: New Zealand
One other thing.....C6 governors, which work together with the modulator to control shifts, can get sticky & this gives shifting problems.
The easy fix is to either jack the rear of the truck onto axle stands, or find an empty road, then drive in reverse for a minute or so. This flushes the tail housing (& the governor) with trans fluid.
I've had to do this with both C6's I've owned once or twice, it's an effective fix if that's the problem.
The easy fix is to either jack the rear of the truck onto axle stands, or find an empty road, then drive in reverse for a minute or so. This flushes the tail housing (& the governor) with trans fluid.
I've had to do this with both C6's I've owned once or twice, it's an effective fix if that's the problem.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,695
Likes: 2,616
From: SE Florida
From a standing start how many shifts do you get? One or two?
Thread
Thread Starter
Forum
Replies
Last Post
SCRWDRVR
Clutch, Transmission, Differential, Axle & Transfer Case
4
Nov 20, 2022 11:53 AM
Bobbytr1ll
1987 - 1996 F150 & Larger F-Series Trucks
5
Sep 26, 2021 10:39 AM
Luis V
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
2
Feb 21, 2021 10:37 AM