Leaking transmission fluid (I think) — ‘74 wagoneer

[FinGoJeep]

I recently purchased my first FSJ, a 1974 Grand Wagoneer, 3 speed auto, 401 with Quadra-trac. It runs and drives great, but coming off the fuel, particularly going down hills, it’ll just puff out bluish smoke. I thought it was engine oil at first, but the transmission fluid level keeps dropping while the engine oil stays slightly more consistent.

I would like to be able to fix it, but I’m not totally sure where to start. Any advice is much appreciated.

[sirrus]

Might be a transmission leak dripping on exhaust? Does it leak when parked? Might be time for a new pan gasket

There is no way ATF can get burned in the engine


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[tgreese]

Can't the vacuum modulator on the transmission leak back into the engine? It's connected by a vacuum line. Vacuum is highest when decelerating. Easy to check for oil. Look in the '74 TSM here https://oljeep.com/edge_74_tsm.html at p. 7-45.

[sirrus]

Oh snap, I keep forgetting about transmissions other than 727 vacuum modulator can actually be a way for ATF to reach the intake


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[letank]

X2 on the vacuum modulator, it has happened to me as well, giant puff of smoke, when you disconnect the vacuum hose at the transmission it will be full of transmission oil. New modulator, there are different version of the modulator, with or without elbow, this is with elbow:



the non elbow works as well, remove the elbow and the insert lever

[TheDarkLord]

Same situation, but my 74 is a 360. The little lever inside is tripping me up. None of the replacements I see for sale or any how to video mentions it.

Can I replace it with one that does not have the lever? Also, it seems my cooler lines enter at a different location than most diagrams I see..



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[letank]

yes you can, the straight will fit