Hi out there. I have been watching the forum for a couple months now and really enjoy and appreciate all the great info. and discussion. I purchased a '70 Ranger a few months ago and am in the process of getting it back to mechanically sound condition before I tear into the body and interior. I started by taking some great advice and put the Holley 500 2-bbl on, what a dream compared to the old autolite that it came with. Runs much smoother and more power. It's got a 360 with what I would assume is the C-6 auto-trans., from what I've been reading. The truck has been running great aside from some lifter noise and tappets-due to the necessity of full lifter replacement. I'm holding out to buy a rebuilt 390 from a buddy in the next few weeks, so I can deal with the tappet noise until then. My main concern is the fact that the transmission, over the past couple weeks began to slip out of gear when coming to a stop and is revving quite high before it shifts up into second. Since this sounds like transmission fluid issue, I checked it and sure enough it was low. So, after seeing that many of you recommended the Dextron III, I bought a few quarts and added them. Checking after each quart, the fluid didn't reach the dipstick yet, but after a few minutes, the thing started blowing thick blue smoke out of both sides of the exhaust, as I have dual exhaust. So, I took it out on the road and drove it until it blew through and stopped smoking. It shifted better, but deteriorated as it seemingly burned off. At that point I wasn't exactly sure if it was the trans. fluid that caused the smoke. So, I added another couple quarts and sure enough it began puking more smoke from both tailpipes. All I can guess is that it has something to do with the transmission vaccuum??? Could it be sucking fluid into the intake? The added fluid did cure the shifting problem, but the smoking is unbearable. By the way, no leaking of trans. fluid. Any Ideas....? Thank you in advance!

 

I don't know that the vacuum connection at the transmisson would allow for fluid to get into the vacuum hose. Maybe part of the hose is torn or burnt near the fluid filler. but, I would think that some would still spill to the ground. Is theer a hole in the exhaust near the filler tube?

I'd pull the vacuum hose and see what happens. Maybe cap it off at the carb. It will shift rough, but you can better diagnose the smoking problem.

You've got me stumped. Hopefully one of the gurus will ID your problem shortly.

 

Sounds like you might have a hole in the modulator valve which will cause it to overspeed and suck up tranny fluid into the intake manifold.

Also, you should use type F fluid unless the tranny has been rebuilt with clutch packs compatible with the Dextron juice.

Barry

 

I concur with the modulator theory.

Also it is my understanding that dextron will cause a type "F" transmission to slip, where as type "F" will only firm the shifts of a dextron trans.

(we could go into the details of the seal swelling and friction properties of each, but its pretty dry stuff.)

B&M actually told me after I put a shift kit in one of those off brand cars (THM400) to use type "F" if I couldn't find any of thier "TrickShift".

FWIW

 

B&M "TrickShift" is Type F with blue coloring.

 

Hey there, thanks all! The modulator problem sounds about right. The tranny is overspeeding from a stop, I actually have to let it overspeed and then let off the pedal for it to kick up into 2nd, 3rd. I'll also look into the "F" fluid. Any tips on getting into the modulator? is this something relatively painless, or am I looking at dropping the tranny. If so, I might as well wait a couple weeks, until I get the 390 from a buddy and tackle it all at once. Is this an expensive part? Can it be replaced with trans. in place? Thanks again! Eric

 

Replacing the modulator is easy, it's on the outside passenger side near the bottom. Follow the vacuum line from the engine, it connects right to it. To remove, just unscrew. You can tell if it was ruptured when you pull off the vacuum hose, it will drip out tranny fluid. Buy the correct one for your tranny and just screw it in and reconnect the vacuum line, that's it.

Barry

 

Wow, thanks soo much, I'll get into that and let ya know how it goes. Eric