automatic gear changes clunky

[ozbowhunter]

can anyone help regarding adjustments to stop the gear change from being hard and clunky ? the transmission was supposedly rebuilt before I got the truck so it may need adjustments?

[geezer#99]

Could be your vacuum modulator is bad or adjusted incorrectly. Or your kickdown is out of adjustment.
Or it might not be the tranny. Could be a bad u-joint.
Here's a pic of where the modulator is.
http://www.teufert.net/t350/t350.htm

[wilkin250r]

Like geezer said, the problem might not be in your tranny. Could be a U-joint, or even in the differential. I've got a real nasty "clunk" when I shift into reverse, and I first thought it was the transmission (largely because of other transmission problems), but crawling under the truck I found out the problem is actually in my front diff.

[Rascal_one2001]

What transmission is in your truck is it a hard shift or does it clunk like the trans mount is bad letting it hit the floor.? Does it do it every time it shifts.

[ozbowhunter]

It does not do it every time sometimes it's seems smooth other times it clunks hard and other times it seems to take a long time to change
These things dont seem to happen all at once just not sure where to start

[InitialBoss]

Originally Posted by ozbowhunter

It does not do it every time sometimes it's seems smooth other times it clunks hard and other times it seems to take a long time to change
These things dont seem to happen all at once just not sure where to start

Does the times it clunks depend on how much throttle you're giving it. I had a hard shift and high rpm shift issue and it boiled down to some vacuum line issues. The trans guy said the vacuum line wasn't connected to the modulator. Wish I saw this before I had the trans guy check it out and fix it. It runs nice now but I wish my engine was a V8 instead of an inline 6. I want more HP. Ha ha.

[Rascal_one2001]

OK still need to know what trans your running. First step is check fluid level with it running
Then check your mounts and drive shaft joints
If you have a th350 make sure you have the vacuum hooked to a direct manifold vacuum normally just behind the carb there is a port in the intake manifold not the carb
Then make sure the line from the intake to the trans is a not rusted or kinked hard metal line with short 2-3 inch vacuum lines connecting it. A full soft line can collapse on it self. After all that if the shifts are erratic you may have a bad modulator or a crappy rebuild

[ozbowhunter]

No problem where and what do I look for to give you the correct trans info ???

[Ski-me]

Originally Posted by ozbowhunter

No problem where and what do I look for to give you the correct trans info ???

I'm also curious about this problem and would like some input too. Mine clunks "sometimes" on harder accelerations when it changes gears, too. Other times, it's smooth as silk.....especially when cold. I just had my tranny re-built and then "re-built" again for missed parts. He also said that he installed a little firmer shift on hard accelerations. New driveshaft, new u-joints, new rear end. Mine is a 700r4, 350 TBI, 9.5" rear end.

Here are some pics to identify your existing tranny based off of the pan.

[ozbowhunter]

ok have had a look and I have a th350 transmission I checked the vacuum lines and they seem ok so my first step is to check the level while running I will for my own peace of mind change the modulator and replace the trans fluid and let you know what happens
thanks for the info