Trans leak only during hard acceleration.

reg GM 3 speed TH350

Though it was the vacuum modulator. wasn't.
Thought I found a bad piece of line. Replaced with steel braided.
Still leaks. Though only during hard accel. The right side and exhaust pipe are wet. It doesn't seam to lose much but smokes like you know what. It seam to leak down to the add a quart line and stops.

 

I had the exact same problem, right side underbody wet, CAT wet and smoking like a damn forest fire (damn embarassing it was ) found my return and send lines were leaking. Put some plumbers tape on the threads now it's been dry for 3 weeks.
Hope your's is this easy to fix dude..

 

Excellent idea.

I had worked on the exhaust system as of late.
Had to drill everything out. Under there allot.
I could of knocked a line lose.

Though all of this is sort of trying to track down why all 7 other plugs are white clean and #6 is not bad but dirty. I though maybe the modulator was bad. So engine vac was sucking up trans fluid and it was going down the #6 intake runner.

Its just been so darn hot here and I work nights.
Other wise id be under it at midnight.

 

Well I am back to thinking its the vacuum modulator or???

#6 plug is still getting dirty fouled out for no reason fast, not oil or other. And it only uses trans fluid under hard accel. If I drive like a granny it last weeks, if not its like ever 3-4 days it needs 1/2 quart of fluid added.

Maybe I was mislead but how the heck can the tans work ok and be leaking fluid like that through the modulator? Would think the trans wouldn't op right.

Can that mod be changed with it on the ground, easy stuff?

Thought of rerouting it though so the vacuum for it come from else where and leave my #6 plug alone. Just needs full manifold vacuum right? Put it on the carb so all cylinders get equal ammounts. if anything, would burn it better till fixed.

 

vacuum modulator is probably leaking, buy a replacement and it's $13 or so. Get an adjustable one if you can they're nicer to adjust shift points. Also it's held on by one bolt and will spill out a little trans fluid when replacing it. You should jack the car up a bit on jackstands...easy 15 minute job.

 

Any tips on the adjustments?

They are all over cheap but I don't see any obvious screw or what not to adjust. Where should one start and how do ya know which way does what?

Or is there a mod that one can buy that is already well set up?

 

the adjustment screw is located where the vacuum hose connects to. Basically you use a very small flat blade screwdriver to turn the modulator. Mine came with directions on how to turn it, in-or-out, to vary the shift rpms. You could vary it 2 turns in or 2 turns out to adjust the shift points. I just asked my local speed shop for a vacuum modulator that was adjustable for a TH350 and he ordered it. Or you could ask for a 76 camaro with a TH350 from your local parts store and it should probably be adjustable as well. Hope this helps

 

From looking around there is a black and red strip mod. Dunno what it means but the adjustables ones I have found are red strip. $12 shipped.

 

check out summit part # SUM-G110 adjustable modulator for TH 350 or 400 $11.95

 

i think i have the red stripe one...it's been a while since i was under the car and not fixing something broken and had time to check out the trans

 

Look at the overflow tube at the top of the transmission and see if the area up there is wet? To find this leak, dry off the transmission with paper towels, now drive the vehicle to make it create the leak, jack the vehicle up, take white paper towels to dry off the transmission and this help you locate the leak. The vacuum modulator you want is the single red stripe. If the part throttle shifts are too early, turn the screw clockwise one turn, go for a test drive & see what happens, if still too early repeat the above procedure. If the shafts are too late, then just the opposite of the above recommendation. Three turns maximum either way from the starting point.

 

Well I finally got a new vac mod but you know the bolt snapped off while trying to get the old one out. And there was no way Im droppin the trans for that. Murphays laws says more crap will break.

Talked someone into getting me a 90* drill attachment for xmas but giving it to me early. Like almost always even the best drill bits don't get anywhere fast. But my handy dandy step drill bits from harborfreight cut through hard and fast.
Then I used a nut n bolt this time. Steel to aluminum threads that are exposed to weather is super hella dumb.

Dunno if all is well yet. Need to change out #6 plug and go tearin around town looking for smoke and low trans fluid level.