I am hoping to get some help or input on the vacuum line to the trans modulator for the above combination. In a recent discussion with a previous owner of this 68 GP, I mentioned that the engine sounded like it was revving higher before the trans would shift into a higher gear. Long story shortened is that I was informed that the original vacuum line to the modulator was replaced as there was issue with the original and subsequently a vacuum line that was 1/4 inch was installed as they were unable to source an original. I was told that the original was a 3/8 diameter and a 1/4 inch was installed and perhaps this 1/4 line was affecting the modulator and shifting.
Admittedly, I do not have a hot clue whether the original vacuum line should be 1/4 inch or a 3/8 inch, so my question is, does anyone have any information as to what size the vacuum line should be for 396 / TH400? Also, could a variation in the diameter also be a contributing factor in shift variation?
The car is stuck in storage for 10 more days so I can't access it immediately for any other info, but wanted to try and get some info on this topic. Also, does anyone have an original part #?
Without looking I'd say it's probably a 3/16 line Jake.
Classic tube, Fine lines or Inline probably has an exact shiny reproduction part. Or just do it yourself with brake line. I don't thing the size will have much bearing on the function of the modulator. Provided the modulator isn't stuck and the hard line and hoses aren't significantly kinked, it should not matter.
Funny you are asking about it, I will be making up that exact line this spring for my engine install, and have been actually thinking about it.
Cheers,
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65 Laurentian post, 67 Grande Parisienne 4 door HT.
Thx for the responses, it gives me some valuable info to explore when I liberate it from storage! 10 days and counting, hope Winnipeg weather cooperates!
There's a couple different configurations, mainly dealing with the fitting on the intake manifold. On most, the fitting has the vacuum port pointing straight at the passenger side fender. However on some, the fitting has the vacuum port pointing almost 45 degrees towards the heater box. Which fitting do you have, and I'll take a look at the vacuum lines I have. (I grab these from the junk-yards as I was missing one on my 2+2 rag when I got it) As GLHS60 mentions above, the ends are reduced.
Hello Seventy2plus2, I am not sure which fitting I have but I will take a look,...in ten days! The car is buried at the moment and I am going to take it out of storage at the end of the month. I doubt I will have a chance to have a look prior to that but your question is something that I am going to look at closely. I will let you know in ten days!
I'm sure I have a reproduction one for the fitting that points towards the heater box, and I'm sure I have a used one for the fitting that points towards the fender.
