Wimpy shift into 3rd

[junkyardjeff]

I have a C-4 that will slide into 3rd with a light throttle and will shift firm when into it a bit,I was told to adjust the modulator screw in a bit so I turned it in two turns and it helped but still wants to slide into 3rd on a light throttle. I noticed it slow to shift the other day when cold so does it look like its time to rebuild. Jeff

[junkyardjeff]

This trans came from a 68 to 74 3/4 ton van that probably had at least 3.73 gears and I have it in a car with 2.79s so could the governor be set for the steeper gears causing it to act that way. Jeff

[nitrowarrior]

Cold problems with engaging into gear is likely gunk in the valve body and keeping the shuttle valves from immediately working. The soft third is possibly worn direct clutches, gunk built up around the lip seals and or low main pump pressure. If I was faced with this, I would pull the pan and see if there is a science project growing inside the pan. If it looks like heavy amounts of debris built up, my recommendation is to build the thing. The steeper gears definitely make these problems become more prevelant.

[junkyardjeff]

I had the pan off and it looked good and the trans looked to have been rebuilt in the past but it came from a junkyard so who knows its history,the more I think about it it sometimes is late to shift when cold and will shift into 3rd decent at a light throttle but starts to slide when warm and its only hooked to a cooler in front of the radiator as the raditor does not have a built in cooler. Jeff

[nitrowarrior]

If it's clean, you might try pulling the valve body and cleaning it. If you're nervous about doing it, have someone you trust or a good shop do it for you. There are valves hanging up most likely from burring inside the bores or silty dirt stopping them from free movement. I wouldn't mind pumping the main line pressure just a bit. I fear sometimes too that the last builder left the clutch clearances a bit to loose. That's why your third gear takes more throttle pressure to hit it well and slides when you're trying to get into third when you're easy on it. Grant it I'm no magician and something else such as an internal leak could be causing it. These are just areas most commonly to be the culprit.

[nitrowarrior]

Intermediate is for second. Unless it's hanging up, it should release instantly. I had thought about the servo sticking on release if that was the case. I feel that would be a rare instance though.

[nitrowarrior]

I ran through all of those and went back to his post. Both descriptions. Just doesn't feel right to me. I'll bet he is due for the band adjustment though. Ya can't get proper servo travel and load if they're out of whack.

[junkyardjeff]

Its been rebuilt years ago and could of sat in the junkyard for awhile too,the reason I think it has been rebuilt is the case was painted blue and a couple local trans shops paint their trans blue. It has been in my car for about 3 years just sitting while I got some body work done,I drove it shortly after installing it and it acted the same so it needs some attention. When it slides into 3rd the RPM goes up some if that will tell anything Jeff

[nitrowarrior]

AH HA.......The rest of the story

[nitrowarrior]

Ever have that phone call at the shop?...."Hello, My car's broke. What's wrong and how much?"

[junkyardjeff]

The fluid was nice and red when it was pulled from the donor vehicle but I drained the fluid and put in new front and rear seals along with a filter before installing it in my car but I wil try adjusting the bands and see what happens,I was just wanting to know if there was any adjustments I could do before taking it out and having someone go through it. I am going to drive it as it is for the summer and take it out in the fall if it lasts that long. Jeff

[junkyardjeff]

I was hoping the huge vacumn leak would improve the shifting but it did not,it shifts fine with a light throttle when cold but as soon as it warms up it starts to slid into gear so I am going to adjust the bands and see if it improves but if it lasts all summer it will be pulled and rebuilt over the winter. Jeff