So I tested the vacuum and the car is idling in park at 19 inches, in drive with brake at 16 inches. I ran a 7/32 vacuum line from the port on the manifold to the modulator. Driving the car in 1st and approaching 2nd it would hit a peak of 3 inches, shift and spike up to 5 inches, immediately shift back down and drop down to 3 inches and repeat. The vacuum changed in perfect sync with up and down shifts. Running just the 7/32 line without anything else in the line seemed to help the downshifting happen less on the big hill here, but it woudl still do it a time or two on flat ground.
Th350 shifting up and down repeatedly on hills.
- Thread starter GBodyVillain
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What is the throttle opening when the 3 and 5 readings are obtained? What RPM is the engine at with the 3 and 5 readings?
What exhaust system is on the car? New? Old? Cat?
It really sounds like the exhaust system is restricted killing the vacuum. Take the head pipe loose and run that hill bet it runs fine. Yes it will sound like hell without the exhaust system.
What exhaust system is on the car? New? Old? Cat?
It really sounds like the exhaust system is restricted killing the vacuum. Take the head pipe loose and run that hill bet it runs fine. Yes it will sound like hell without the exhaust system.
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Ref those comparison shots, the second picture showing the pans. The other clear difference is that the 350 case shows the modulator valve that it uses for vacuum delivery at the case. The TH200 doesn't have that, and the case has no place on it for one.
Under the car, looking up, you would slide under from the passenger's side and the modulator valve would be facing to the rear, on your left side, just ahead of the crossmember. It should have a short length of re-inforced rubber hose attached to it and then to the steel vacuum line that heads forward along the case and then up behind the bellhoussing bolts on its way to the vacuum line fitting screwed into the manifold just in front of the distributor.
As suggested you can make one or possible do a Pick a Part run and find one still in a hulk. Often they will get left behind if the only thing being taken is the engine.
Nick
Under the car, looking up, you would slide under from the passenger's side and the modulator valve would be facing to the rear, on your left side, just ahead of the crossmember. It should have a short length of re-inforced rubber hose attached to it and then to the steel vacuum line that heads forward along the case and then up behind the bellhoussing bolts on its way to the vacuum line fitting screwed into the manifold just in front of the distributor.
As suggested you can make one or possible do a Pick a Part run and find one still in a hulk. Often they will get left behind if the only thing being taken is the engine.
Nick
It is not a transmission problem, the transmission is working properly with vacuum signals that are out of range for its design. The engine has a vacuum problem and my best guess is it has a clogged exhaust system.
I recently had a clogged cat and muffler. The pieces of the honeycomb had clogged everything so bad the car would barely idle. Everything from the cat all the way back has been replaced. A vacuum problem I can see though I've no clue where to look. I've recently had the dash out and tested everything behind it and found no leaks using some carb cleaner. I can go through everything in the engine bay but I'd like to route everything correctly and use all the correct fittings and correct size lines and get rid of this cobble web of lines once and for all. I did some searching during lunch today and couldn't find any for sure answers on what is correct other than the smog related routes.
What is the vacuum at wide open throttle? How long does it take to build the vacuum back up?
How does it run at high speed?
Have you checked the EFE valve on the exhaust manifold (looks like it has a crossover pipe and the EFE is on the passenger side) is it rusted closed or jammed with something?
How does it run at high speed?
Have you checked the EFE valve on the exhaust manifold (looks like it has a crossover pipe and the EFE is on the passenger side) is it rusted closed or jammed with something?
At wide open throttle the vacuum drops to around 2 to 3 inches. It seems to build back up at a rate of 2 inches per second though I'd have to go back and verify this. At high speed the motor runs strong. As for the EFE I'm not familiar with what that is. It's extremely crowded on the passenger side by the exhaust and I'm not sure about what it is I'm looking for.
Okay, that's on the driver side out in the open. It never worked and I took it out to check what was up with it when I first got the car and its welded in the open position. I deleted the vacuum lines to it as well as the fitting that controls it that goes into the block and plugged up the hole. I couldn't buy a new one back then and I doubt I can get one now. I pass smog without it so I'm not worried about getting one.
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