PLEASE HELP!!! 1987 F350 6.9L 3-speed auto

[bcafferata]

Hey guys,

PLEAAAAASEEE HELP ME!!!

I have a 1987 F350 4X4 6.9L N/A with a 3 speed automatic transmission. The problem is my trans has a real hard time shifting, and after it shifts, it will down shift whenever it wants. I thought it may have been the vacuum actuator on the side of the trans so i decided to take it to my trans guy. He took a look at it and told me that the actuator is holding perfect PSI and nothing is wrong with the trans. He also said that the motor is not putting out enough vacuum to the actuator to shift the trans. I dont understand this because correct me if i am wrong, diesel's don't make vacuum. If anyone knows what i can do, or if anyone else has had this problem and maybe you could help me out, i would really appreciate it!



Brandon

 

[hesutton]

There is a vaccum pump driven by a belt on the front of the motor under the alternator. If the pump is bad or there is a vaccum leak, that may be the problem. I don't know a great deal about the vaccum diagram for the C6, but someone else will be along shortly.

Heath

 

[Agnem]

Get yourself a vacuum gauge and add it to your insturment cluster. Both your ability to shift, and your ability to stop depend on good vacuum! You should have about 23 inches of mercury at sea level. The VRV on your IP may be going bad as well. There is a test for this, but I don't have it in front of me.

 

[bcafferata]

thanks buddy appreciate it

 

[david85]

x3, as mentioned you need to verify that vacuum is getting to your transmission controls. I limped my C6 transmission home several times when ever an alternator belt would fly off.

Probably not a major problem. If your power brakes are working then I would be looking at all the lines related to the transmission to make sure there are no leaks. The way the system is designed, high vacuum causes early, soft shifts, while low or zero vacuum causes late hard shifts.

The advantage of the system is the transmission will limp in a fail safe mode at the hard grabbing end of the shift map instead of the soft mushy end where slipping could occur.

 

[icanfixall]

Well... All the above postings have clearly pointed you in the correct direction.... Post back if you get it fixed or need more help... I'm kinda going with the VRV thats found on the drivers side of the injection pump

 

[Brianedwardss]

VRV x3, but... check the kick-down lever as well, had mine pop loose at the IP once and do this. I will assume the transmission gave it a look, but ya' never know