I have a 98 dodge cummings with a automatic tranny an my over drive is going in an out but when i have the over drive off it does not do it. If i have the over drive on an on the highway it is fine but if i get on it it starts going in an out. Can anyone help me?

 

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OD clutches are probably gone or the converter slipping, fluid smell burnt brownish color?

 

i dont think so i checked it an it looked good

 

Well, the torque converter has a TCC clutch switch which engages in fourth gear. It also is engaged in third gear with OD switch off on level ground cruising. When you Get on it you said it does it also, so in that mode the trans is kicking down to third.The TCC is controled by the PCM it would be a good place to start > the TCC is a solonoid check the plug on the trans maybe a loose conection.

 

ok ill have to check that thanks ill let you know

 

You may be experiencing convertor lock and unlocking in 4th gear (OD).This is caused by electronic noise that the alternator puts out.To fix this clean ALL your battery cables pos. and neg side.Even the ones on the block. If that does not fix it DTT sells a noise filter that is a 10 min job to hook up.This is a common problem TC lock and unlock.Hope this helps.

 

That is an option, I would clean all your ground cables to begin with and go from there. If you search around you can find alot of articles on this and many different types of solutions that have helped some. I had the same issue, but I just did a ground wire splice from my apps. There is a write up on here, try the keyword suncoast in the search and you will have to start reading, but should find it. Hope you get it squared away.

 

also check the tranny fluid, make sure it is full, check it with the truck idling in NEUTRAL..... in park it will read full but be 1-2 quarts low..... i speak from experience.....