Hello,

'90 Vert - Automatic (I love the car, I hate the transmission)

Has anyone ever heard that a vacuum leak or missing vacuum line can cause the transmission to slip and hard shift?

The reason I ask is I was told this by a Rotary shop after I first got my 7. When I first got the car the transmission was slipping very badly. They told me that they found a line off and that should help the shifting problem.

It was considerably better when I got it back, but the fluid and screen were changed and I put some treatment into it. So I don't know what made it better.

Recently I had the UIM off to replace a broken OMP line and ever since the transmission is back to slipping, hard shifting and shifting at very high RPMs. I haven't been able to find a leak, though.

Any input is appreciated.

Thanks.

 

Well I would't know because I have the manual, but there are some AT specific vacuum lines on the throttle body which may screw up the shifting if not connected properly. I would just open your hood and look around the throttle body for anything that looks astray . . look carefully and you might find the problem.

Most of us don't have the AT sevens because they are slower and we don't like slow cars.

 

i also have a similar problem.... let me know if you get a definite solution.....

 

Yes, there is a single vacuum line that is connected to the transmission. If this line is not connected, or becomes clogged, the transmission wil not work properly and will begin to slip and mis-shift. The result of this is transmission failure unfortunately. Just swap out that piece of ****. The automatic transmissions used in those cars are complete garbage.

 

There is 1 vacuum source for the auto trans at the UIM.
Check if the vacuum line is cracked or nor connected and check the vacuum diaphram. A malfuntioning of the diaphram will cause mis-shifting.

 

my slippnig seems to happen during cold starts only.. when the car has been driven for like lets say 10 mins.. then it seems to dissapear... the time its most noticible is when i get outta my parking spot and like punch the gas sometimes...

 

In some ways I hope that the transmission will go out totally so I will be forced to do the swap.

I'm on the look out for an affordable donor now.

I'll recheck all of my lines and let you know how it goes. It has to be something like that because it was shifting fine (or better I should say) before the latest repair.

Thanks

 

before you give up on the trans totally try putting some brake fluid in it.. it saved the transmission on my '91 tempo..

 

X3delight, change the fluid and filter and see what happens...

 

I see the Vacuum Diaphragm in the FSM, but where on the UIM does the line hookup?

Thanks in advance.

Brake fluid in the transmission? I've never heard of that. How much did you put in?

 

Your problem came up after you installed the UIM . Re-check the vacuum hoses and the check valve.
The vacuum hoses are near the throttle body.