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Post by Deleted on Sept 12, 2019 9:03:24 GMT -5
The Jetaway transmission in my 65-442 was rebuilt in 2010, but due to illness only 900 miles have put on it since the rebuild. The issues I am having are:
1) Under low to mid throttle acceleration from a standing start with selector in "D", there is a hesitation between the 1 to 2 up shift. Engine has a slight rev increase between the shift.
2) Again with selector in "D", coasting to a stop the downshift has a hesitation from 2 to 1, engine also revs between the downshift.
Talking with some fellow cruisers, they mentioned timing, vacuum could affect this. I knew the original Rochester 4GC was worn out, including the throttle shafts, so I installed a new Edlebrock 1406 carb, adjusted timing to factory specs since the 400 is stock, replaced all vacuum hoses and the vacuum is @ 14.
Any and all suggestions would be appreciated, and FYI I am not a trans guy, but can handle all the other mechanical components of the 65-442.
Thanks!!
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Post by shane on Sept 12, 2019 10:38:22 GMT -5
Engine vacuum should be between 18 and 21. Something isn’t correct if your only getting 14.
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Post by Deleted on Sept 16, 2019 9:40:01 GMT -5
Okay, I will do some deeper diagnosis, Thanks.
I did a compression check, 7 cylinders are 160#, the other 165#. From what I can find out the compression for the 65-442 400cu. in., is suppose to be @ 180-185. Not sure if this would contribute to lower vacuum?
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Post by joepadavano on Sept 17, 2019 7:50:41 GMT -5
Absolute compression readings are far less important than consistency from one cylinder to the next. Your engine is fine.
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Post by Deleted on Sept 23, 2019 8:11:58 GMT -5
Thanks, will continue to see what is causing the vacuum to only be 14"
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Post by island65cruiser on Sept 28, 2019 13:10:53 GMT -5
When I put a Speed Demon Carb on my stock 442, with Jetaway, I connected the vacuum line to the wrong port on the carb base and had the same problems you are describing. You need the port that draws full vacuum all the time, not the one that is ported above the butterflies in the carb. Hope this helps.
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Post by Deleted on Oct 6, 2019 23:58:32 GMT -5
Thanks for reply. Currently, the vacuum modulator line is connected to a port on the intake manifold which should be full vacuum, correct?
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Post by island65cruiser on Oct 9, 2019 19:37:05 GMT -5
Yup, it should be. Are you pulling enough vacuum there? Does the car idle OK, have you checked for vacuum leaks? I am not a tranny guy, but could it be the modulator itself? Have you checked the wiring for the "switch pitch" converter? My solution for puzzling auto trans problems is to install a 4 speed!
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Post by jims442 on Oct 9, 2019 19:45:10 GMT -5
I agree install a 4 speed,there is nothing like banging through the gears,my wife told me if your going to have a muscle car it has to be a 4 speed
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Post by island65cruiser on Oct 11, 2019 20:07:22 GMT -5
And, your car is absolutely safe from Millenial and younger car thieves who can't manage three pedals!
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Post by Deleted on Nov 29, 2019 21:22:30 GMT -5
A vacuum modulator is NEVER connected to manifold vacuum. It is connected to port vacuum. The modulator regulates the pressure according to throttle position the faster you go the more line pressure slower less line pressure. Hard up shifts and down shifts your connected to manifold vacuum.
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Post by joepadavano on Nov 30, 2019 8:38:25 GMT -5
A vacuum modulator is NEVER connected to manifold vacuum. It is connected to port vacuum. The modulator regulates the pressure according to throttle position the faster you go the more line pressure slower less line pressure. Hard up shifts and down shifts your connected to manifold vacuum.
Sorry, but you are incorrect. Check the factory Chassis Service Manual, which clearly shows the trans vacuum modulator connected to straight manifold vacuum. You also should refresh your understanding of ported vs. manifold vacuum. The only difference between the two is at idle and small throttle openings. Once the throttle blades in the carb uncover the ports in the throttle bore, ported and manifold vacuum are exactly the same.
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Post by Deleted on Dec 11, 2019 21:24:57 GMT -5
"You also should refresh your understanding of ported vs. manifold vacuum".
Getting old and feeble. Embarrassed by my first post here. Used to rebuild rear wheel drive transmissions back in the day in a professional shop. Just shot from the hip on this one without thinking.
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