Quadratrac (1339) upgraded vacuum lines? Or mods?

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JohnnySwell
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Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by JohnnySwell »

Pulled apart the dash to clean up my 78 Chief and fix up wiring and found my vacuum lines to the 1339 are destroyed. Looking to get some info or ideas on what you guys have done for replacing the lines or upgrading them. I’ve hear of people using brake lines or something more durable than the OEM rubber lines.

I saw a video where this guy converted the vacuum system to a linkage system. Seems like a decent upgrade. You can see this starting at 10:20 in the video below:

https://youtu.be/DfOESXGTe5s

Would appreciate any advice or input.


-Johnny


Sent from my iPhone using Tapatalk
Johnny B

1978 Cherokee Chief

I'd love some input on my build here:
https://www.fsjnetwork.com/forum/viewto ... 12&t=20266

letank
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Re: Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by letank »

rubber lines work fine... some Year Model had steel lines running against the firewall and the under carriage, but still using rubber hose at input and output ...

IIRC the limiting factor is the vacuum control unit on the QT transfer case.

Many years ago, my dash switch failed... and at this time there was no availability, so I used a 3 way stopcock.
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)
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Stuka
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Re: Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by Stuka »

You have to connect with rubber lines at some point, even if you use steel in between. The only maybe advantage that I can think of for steel is if you have mice that constantly chew through the rubber lines.

Jeep did use a cable actuated system for one year, and then promptly went away from it. As I recall you would have to mess with it a bit to get it to shift. With a vacuum actuated switch you just send vacuum, and it will shift it as soon as the teeth are lined up. The mechanical setup in the video is neat, but it has a flaw. Normally mechanical linkages use another piece between the shift rail, and the shifter arm. Because as its setup in the video, its going to be pulling the arm up and down as it goes in and out. Which means the seal around the shift rail is probably going to fail, and may actually cause internal wear.

I honestly don't see anything wrong with the vacuum setup provided things are working correctly.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
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fulsizjeep
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Re: Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by fulsizjeep »

It is easy to confuse what is shifting what. The cable shifter for low range was 73-75, flag shifter is 76-79. The Edrive vacuum shifter was always for Edrive if stock QT or 2wd/4wd for the part time kit. I have had good experiences with the vacuum shifting device.
Flint Boardman
88 GW, 401/727/208, 5" lift, D44s/4.10s/locked up, 35s
https://jubileejeeps.org/quadratrac
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Stuka
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Re: Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by Stuka »

fulsizjeep wrote: Tue May 04, 2021 5:27 pm It is easy to confuse what is shifting what. The cable shifter for low range was 73-75, flag shifter is 76-79. The Edrive vacuum shifter was always for Edrive if stock QT or 2wd/4wd for the part time kit. I have had good experiences with the vacuum shifting device.
Ahh, you are right of course :)
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Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
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1978J10REDWHITE
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Re: Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by 1978J10REDWHITE »

I went thru all this also.
Mine has the metal tubes with rubber tun[bes to it factory.
Replaced every rubber hose including under hood and under dash.
I also had to put a tywrap on the metal tube ends & Diaphram to ensure zero air leakage,
It is easy to verify the glove box Switch so do that to know it does switch properly.

The cable uprade is actually a good idea, this vid is crappy example yet enough to give you the idea.
I measured mine in a 78 J10~360 With TH400, and the length appears to be dead on at 7 length feet total , In case you decide a reference point length you wiley will need o near that.
I may still do this, having looked at the cables online, the one I found are very sufficient and weld up the bracket is easy to have done or do.

The cable is the next best thing as a lot of time the vacuum diaphragms leak and are jonk so cable set-up here we come!!
It’s a matter of just do it.

BJ’s makes a great 2X4 conversion kit to rid the QT-TC of the "cone mechanism” inside, The OEM cone setup that are OK but not Great”, , plus you want to get the hub engage pieces too anyway.
Something to consider.
, I got one yet am in limbo about doping it yet will likely.
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fulsizjeep
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Re: Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by fulsizjeep »

Personally not a fan of the 2x4 conversion and 16% OD is a joke unless you are a mall crawler. Living in Colorado produces all kinds of road conditions and if you drive your FSJ much like we do, full time 4WD is nice to have and we feel safer.

I recently helped a friend find vacuum problems for his QT w/PT kit. It turned out the steel lines were plugged up so he ran all new rubber lines from glove box switch to the vacuum shifter.

Finally, the weak spot in the PT kit is in the 4wd coupler...
Image
I have seen a few like this. One of the symptoms is the QT will not stay in 4WD.
Flint Boardman
88 GW, 401/727/208, 5" lift, D44s/4.10s/locked up, 35s
https://jubileejeeps.org/quadratrac

letank
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Re: Quadratrac (1339) upgraded vacuum lines? Or mods?

Post by letank »

X2, as above, the 16% is bad... upon recommendation in 1988, I went from 3.07 to calculated 2.78... a real challenge touring the sierras... and the 74 had a 1.08 stock venturi which yielded amazing mpg... when the gas was real gas.

As for the coupler, Frank Almaas in Norway reported the same issue years ago... and his solution was to extend some of the splines by welding addon... unfortunately his site is MIA... could not find any link at this time.

http://www.ifsja.org/forums/vb/showthread.php?t=48571
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)
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