Vintage Mustang Forums banner
  • Hey everyone! Enter your ride HERE to be a part of this month's Ride of the Month Challenge!

1 - 17 of 17 Posts

·
Registered
Joined
·
12 Posts
Discussion Starter #1
To start I just had the Transmission rebuilt...the guy at the shop said he couldn't get it started.So I went to the shop and finally got it started but it wouldn't idle, so got it going enough that I followed him to my place. Long story short I did a tune up and got it to idle correctly. So now when I put it in any gear the vacuum drops and the engine dies. I'm at my whits end chasing this ghost.
I'm thinking it may be the torque converter, but the transmission guy says he put the new correct stock converter in(but what do I know). He did limp it back to my home.
The VACUUM is a little low 11hg, I pulled the vacuum line off the manifold going to the shift modulator and vacuum dropped to 7hg. But when I shift to any gear (with modulator line hooked up) the vacuum goes down to under 5hg and the motor dies. Any and all help would be more than welcome.

66 Mustang 289 with a 2 barrel carb.
 

·
Registered
Joined
·
2,134 Posts
That vacuum reading does sound kinda low but if someone was working on it it they could have bumped something unrelated to the transmission so it could be anything.

Do you have a tach? What's your idle speed in park once you get it running?

If you unplug the vacuum line to the modulator and plug it what's your vacuum reading? You said you pulled it off but you didn't say you plugged it for your reading.

What other vacuum accessories do you have? Try unhooking those and plugging the ports. It could be that today is the day your distributor diaphragm, brake booster, swing away steering or AC controls just happened to die.

When you're looking at all the vacuum lines look close at any little plastic "T"s. They can break but still look ok at first glance.
 

·
Premium Member
Joined
·
6,084 Posts
Check the tiny 90 degree line at the trans steel line and the modulator valve, and the connection at the steel line / ferrule to the intake manifold. What about power brakes and a tee that goes to the booster? Good luck...
 

·
Registered
Joined
·
12 Posts
Discussion Starter #4
I've set the rpm to various speeds 800 to 1000 rpm with no difference, still dies. There is no brake booster and no tilt wheel. I have cecked the line going to the trans modulator and it is good. and yes someone did mess with the tranny, newly rebuilt and new torque converter.
 

·
Premium Member
Joined
·
13,214 Posts
Disconnect the vacuum line going to the transmission and plug it off. Now start the engine and check your vacuum reading. If it is not around 20" you have engine problems that are not related to the transmission. Get your engine problems fixed and then add the transmission back into the equation.
 

·
Registered
Joined
·
12 Posts
Discussion Starter #6
Stupid question...Is that 20 in Hg or 20 cm Hg.
If I just can't get up, does that mean the valves are shot ?
Also this is a california car so it has a smog pump. so coming off the carb spacer it goes to the PCV valve and the smog pump.
Maybe I'll try to eliminate that next.
 

·
Registered
Joined
·
1,200 Posts
If you are only getting 11hg on a stock motor and cam then something is not right.


I would start over setting timing with a vacuum gauge or find another mechanic.

<style></style>
 

·
Premium Member
Joined
·
13,214 Posts
Stupid question...Is that 20 in Hg or 20 cm Hg.
20 in. Hg.

If I just can't get up, does that mean the valves are shot ?
https://www.onallcylinders.com/2015...d-a-vacuum-gauge-to-pinpoint-engine-problems/

Also this is a california car so it has a smog pump. so coming off the carb spacer it goes to the PCV valve and the smog pump.
Disconnect all vacuum hoses and cap off the ports. If your vacuum is normal in that condition reconnect the vacuum hoses one at a time until you find the culprit.
 

·
Registered
Joined
·
507 Posts
I had the same issue after I added a new cam. I had to get a 2600 stall torque converter. Could also be a vacuum leak.
 

·
Registered
Joined
·
12 Posts
Discussion Starter #10
Thanks for all the information from all. It just strikes me funny that before the tranny build and the new converter I STILL ONLY HAD ABOUT 10 in HG and the other trans worked fine. PROBLEM WAS THE REVERSE BAND WOULDN'T STAY LOCKED IN (bad seal)
 
  • Like
Reactions: myfirstcar66

·
Premium Member
Joined
·
6,084 Posts
Thanks for all the information from all. It just strikes me funny that before the tranny build and the new converter I STILL ONLY HAD ABOUT 10 in HG and the other trans worked fine. PROBLEM WAS THE REVERSE BAND WOULDN'T STAY LOCKED IN (bad seal)
Congrats on getting it fixed and many happy miles to you !
 

·
Premium Member
Joined
·
13,214 Posts
It just strikes me funny that before the tranny build and the new converter I STILL ONLY HAD ABOUT 10 in HG and the other trans worked fine.
If you only have 10" of vacuum you either have a radical camshaft or another engine problem. So do you have a radical cam?


Congrats on getting it fixed and many happy miles to you !
I don't see that he got anything fixed. Maybe the trans is fixed but he can't keep the engine running to find out.
 

·
Premium Member
Joined
·
6,084 Posts
Oh, I see. I think. Still only 10inHg? Maybe a really lopey cam... It was enough before and now that isn't enough? What about an internal trans leak, then?
 

·
Registered
Joined
·
12 Posts
Discussion Starter #15 (Edited)
Everything is stock, no engine work. completely stock with only 53k original miles. Everyone I talk with says the same thing as Fitch, BAD TORQUE CONVERTER. I asked the guy that rebuilt the transmission what the stall speed was and all he would say is that it was the stock converter. But I don't even know what the stock stall speed should be. Irregardless in gear, any gear, it kills the motor. I think I will go have another talk with him next week.
 

·
Premium Member
Joined
·
13,214 Posts
Everything is stock, no engine work. completely stock with only 53k original miles. Everyone I talk with says the same thing as Fitch, BAD TORQUE CONVERTER.

Believe me, please.

If your stock engine is only pulling 10" of vacuum at idle you have a problem. And it is NOT the transmission. The trans/torque converter is not doing anything with the engine idling and the trans in P or N.
Find out why your engine can only pull 10" of vacuum.
 

·
Registered
Joined
·
12 Posts
Discussion Starter #17 (Edited)
Believe me, please.

If your stock engine is only pulling 10" of vacuum at idle you have a problem. And it is NOT the transmission. The trans/torque converter is not doing anything with the engine idling and the trans in P or N.
Find out why your engine can only pull 10" of vacuum.
I understand, so tell me this. If i advance the timing a little and adjust the idle to attain 15" of vacuum why does it still stall the engin ???

And like previous stated. Prior to any transmission work I only had 10" of vacuum and it never stalled.
Maybe I should try a different vacuum gauge, It could be bad.
 
1 - 17 of 17 Posts
Top