How much more oil in my tranny?

[Norcal1972K5CST]

My truck is going into reverse no problem, but not any forward gears. Tranny was just rebuilt and has less than 10 k miles prior to it being parked for a couple years. I don't trust the dipstick as it says it's full and if I remember correctly I always needed to go past the full mark on that dipstick when I did drive the truck. I just don't want to keep adding fluid and do some damage possibly. I was just wondering if anyone has come across this problem with the TH 350 before? Thanks!

 

[diesel4me]

If you overfill it,it will peuke out the excess thru the breather vent--its not good to run one overfilled as it will foam and air in the trany can cause slippage and other problems--having said that,I have a few friends that had the dipsticks be the wrong ones and they just filled the tranny till it "vented",then sucked out about a pint with a turkey baster and a hunk of fuel line and their trannys held up OK..

BTW,the engine must be running to check the fluid level--I had many customers come into the junkyard looking for a trany,and they didn't know you had to have the engine running and in park to check it-when the engine is off the tranny might appear full,but thats because the torque converter dumps its fluid back into the pan when the engine stops--when you start it it'll read empty on the stick!...you probably knew this,but just in case you didnt---!..

You could have stuck valves in the valve body if it has sat a long time possibly...

 

[Amtek]

Seems like its low on fluid since reverse is working but foward is not.

Exactly as diesel said, you must check it only with the engine running. Get in, start the engine, keep your foot on the brake and shift through all the gears waiting at least 3 seconds in each before putting it in park again but leave the engine running and check fluid level. If nothing shows up on the dipstick, shut the engine off and add 1/2 a quart at a time. Start the engine, shift through the gears and check again and repeat the process until it starts showing up on the dipstick. Make sure at least 4-5 minutes pass from the time you've added fluid to the time you check the fluid to give the fluid to drain from the dipstick tube completely so you wont get false readings.

I made the same mistake after replacing the torque converter with one with a slightly higher stall. with the engine off, the dipstick marked full. The transmission would shift into reverse but any forward gear would be extremely weak. Ended up having to add 3 more quarts to get the oil to appear on the dipstick with the engine running.

And if you think you have overfilled the transmission, just remove the vacuum modulator on the side and the fluid should be flush with the hole. If its overfilled, it will leak out from there. Do not run the engine without the modulator attached!

 

[4xcrazy]

Thought 1st and reverse used the same valving/clutches or whatever they are called.... if no forward, then he shouldn't have reverse.

 

[Amtek]

Reverse runs at a higher pressure. But if he left it in reverse for any length of time, it would eventually start slipping too as the fuild foams up from sucking in air. It would probably also then start foaming/puking fluid from the dipstick, which could be confused for an overfilled transmission.

 

[owenst7]

I'm betting on the valve body. Either a jammed valve or that stupid s-shaped linkage got stretched/compressed and is out of whack...the fluid level is definitely relevant here but if reverse is operating than the reverse piston should still be giving you some response in low (operates in L and reverse).

When you pull the pan, you can figure out where the dipstick is in relation to what full actually should be. Fluid should not be above the casting hole under the first set of clutches behind the pump. Fluid drains through there back in to the pan, so your dipstick full mark should be somewhere below there when it's sticking through the grommet in the casting.

 

[Norcal1972K5CST]

Yeah it was idling when i checked it. I appreciate all the input, i'll check all those things out and see what happens. Thanks again!