hubcityford Posted May 28, 2021 Share Posted May 28, 2021 In my rehab I went and had my transmission serviced as it shifted from park to gear rough and some leaking. They changed modulator and replaced leaking seal. They mentioned modulator could push fluid into engine if too bad. Can someone explain and also is there anything I should do if fluid was going to engine…like change oil? He said that they would change everything and clean it up to observe and also drive to see if it was better. Got call today saying ready so I assume they found no other problems. Just want to prevent something happening with engine if trans fluid got in. Next is the AC!!! South Mississippi is already getting hot!! Thanks Jeremy Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 28, 2021 Share Posted May 28, 2021 I'm not au fait with the C4, but if its modulator is like that of the C6 then it is controlled by engine vacuum. So if the modulator gets a hole in it the engine vacuum sucks ATF from the transmission into the intake manifold. It is usually just a little bit and it doesn't hurt anything but will create smoke. As for the A/C, mine is getting serviced tomorrow. I hope! Link to comment Share on other sites More sharing options...
hubcityford Posted May 29, 2021 Author Share Posted May 29, 2021 I'm not au fait with the C4, but if its modulator is like that of the C6 then it is controlled by engine vacuum. So if the modulator gets a hole in it the engine vacuum sucks ATF from the transmission into the intake manifold. It is usually just a little bit and it doesn't hurt anything but will create smoke. As for the A/C, mine is getting serviced tomorrow. I hope! I was starting to get smoke so hopefully that will be eliminated now. Going to pick up in the morning. Thanks for reply. Jeremy Link to comment Share on other sites More sharing options...
Rusty_S85 Posted May 29, 2021 Share Posted May 29, 2021 I'm not au fait with the C4, but if its modulator is like that of the C6 then it is controlled by engine vacuum. So if the modulator gets a hole in it the engine vacuum sucks ATF from the transmission into the intake manifold. It is usually just a little bit and it doesn't hurt anything but will create smoke. As for the A/C, mine is getting serviced tomorrow. I hope! Funny enough mine was bad on my truck for about 6 years I never knew it cause the truck never smoked but I had a problem with the vacuum hose getting super soft and falling off the vacuum tree. I didnt know what was happening but one day I realized what was happening and replaced it as well as did a band adjustment and pan gasket as I was tired of adding a quart of transmission fluid every oil change. Link to comment Share on other sites More sharing options...
grumpin Posted May 29, 2021 Share Posted May 29, 2021 Funny enough mine was bad on my truck for about 6 years I never knew it cause the truck never smoked but I had a problem with the vacuum hose getting super soft and falling off the vacuum tree. I didnt know what was happening but one day I realized what was happening and replaced it as well as did a band adjustment and pan gasket as I was tired of adding a quart of transmission fluid every oil change. Now you have me wondering. I replaced some very soft hoses that would fall off. Couldn’t figure out why someone would put those on. Going to have to look into this! Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 29, 2021 Share Posted May 29, 2021 Funny enough mine was bad on my truck for about 6 years I never knew it cause the truck never smoked but I had a problem with the vacuum hose getting super soft and falling off the vacuum tree. I didnt know what was happening but one day I realized what was happening and replaced it as well as did a band adjustment and pan gasket as I was tired of adding a quart of transmission fluid every oil change. Now you have me wondering. I replaced some very soft hoses that would fall off. Couldn’t figure out why someone would put those on. Going to have to look into this! Hadn't thought of that, but hot ATF would tend to cause the hoses to swell and I can see them falling off due to that. Link to comment Share on other sites More sharing options...
Rusty_S85 Posted May 30, 2021 Share Posted May 30, 2021 Funny enough mine was bad on my truck for about 6 years I never knew it cause the truck never smoked but I had a problem with the vacuum hose getting super soft and falling off the vacuum tree. I didnt know what was happening but one day I realized what was happening and replaced it as well as did a band adjustment and pan gasket as I was tired of adding a quart of transmission fluid every oil change. Now you have me wondering. I replaced some very soft hoses that would fall off. Couldn’t figure out why someone would put those on. Going to have to look into this! Yep the hoses would get swollen, soft and very limp. Almost like cooked pasta. I ended up using a ziptie to hold them on cause I couldnt figure out what was going on. Then I replaced the shift modulator and replaced the hoses and it never happened again. Vacuum hoses are not rated for chemicals like ATF or oil so after a bit the fluids attack the hoses. Hadn't thought of that, but hot ATF would tend to cause the hoses to swell and I can see them falling off due to that. ATF in general I think causes it. I think its a chemical reaction between the vacuum hose rubber and the fluid itself. Vaccum hoses state they are not for automotive fluids such as engine oil, which I think also includes ATF. Mine didnt really swell too much, they swelled some but they generally became super soft and just the weight of the hose would cause it to fall off the firewall mounted vacuum tree as the rubber was now so soft it couldnt hold onto the barb. Link to comment Share on other sites More sharing options...
grumpin Posted June 5, 2021 Share Posted June 5, 2021 Funny enough mine was bad on my truck for about 6 years I never knew it cause the truck never smoked but I had a problem with the vacuum hose getting super soft and falling off the vacuum tree. I didnt know what was happening but one day I realized what was happening and replaced it as well as did a band adjustment and pan gasket as I was tired of adding a quart of transmission fluid every oil change. Now you have me wondering. I replaced some very soft hoses that would fall off. Couldn’t figure out why someone would put those on. Going to have to look into this! Yep the hoses would get swollen, soft and very limp. Almost like cooked pasta. I ended up using a ziptie to hold them on cause I couldnt figure out what was going on. Then I replaced the shift modulator and replaced the hoses and it never happened again. Vacuum hoses are not rated for chemicals like ATF or oil so after a bit the fluids attack the hoses. Hadn't thought of that, but hot ATF would tend to cause the hoses to swell and I can see them falling off due to that. ATF in general I think causes it. I think its a chemical reaction between the vacuum hose rubber and the fluid itself. Vaccum hoses state they are not for automotive fluids such as engine oil, which I think also includes ATF. Mine didnt really swell too much, they swelled some but they generally became super soft and just the weight of the hose would cause it to fall off the firewall mounted vacuum tree as the rubber was now so soft it couldnt hold onto the barb. Decided to check out my vacuum modulator today. Thought I’d pull the vacuum line off and see if it was moist, but got a little shower! Put a new one in and it drives great. Glad the rod stayed in my old modulator, that could be easily missed. Had a bit of a hard time getting the rod back in. Put it in so I could feel it better, then put the new modulator on the rod and it slid in nicely. Thought it would be a quick and easy job, but not so, took awhile and a bit messy. Glad you mentioned those hoses Rusty. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 5, 2021 Share Posted June 5, 2021 Decided to check out my vacuum modulator today. Thought I’d pull the vacuum line off and see if it was moist, but got a little shower! Put a new one in and it drives great. Glad the rod stayed in my old modulator, that could be easily missed. Had a bit of a hard time getting the rod back in. Put it in so I could feel it better, then put the new modulator on the rod and it slid in nicely. Thought it would be a quick and easy job, but not so, took awhile and a bit messy. Glad you mentioned those hoses Rusty. I guess it was a bit more than "moist"? I'm sure the engine has been burning a bit of ATF. It will thank you, as will the hose. Link to comment Share on other sites More sharing options...
RenoHuskerDu Posted June 6, 2021 Share Posted June 6, 2021 Some folks burn ATF on purpose, with the belief that it cleans the intake tract. I doubt that it has caused any damage to your motor. We fill diesel fuel filters with ATF on change time to clean injectors. Good to see you replaced that modulator. Link to comment Share on other sites More sharing options...
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