Trans plumbing question
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Junior Member
Joined: Mar 2013
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Trans plumbing question
Question on how the plumbing works on a 4R70W. I have an 01 screw with 5.4m, 115k miles. Last year in spring I was pulling my boat (3000lbs) and was blowing fluid out the trans like mad. I had a very reputable local trans guy look at it and he couldn't find anything unusual, but said it was running hot. He installed a HUGE cooler in place of the stock cooler and I installed an Edge so I could monitor the temp. Runs 80Deg F over ambient in normal driving, up to 120deg F over ambient when pulling boat, but still blowing fluid. Looked at it very closely today and the vent line is dry as a bone. Noticed a small hole in the dipstick tube and lots of fluid below it. Is it possible that the fluid is going half way up the tube and leaking out, without coming out the vent tube? It's also VERY wet on the drivers side where the linkage goes into the trans.
Second, why does the trans oil line run through the side of the radiator? Is that to heat fluid in winter or shed heat before going to the cooler? Which line coming out the passenger side of the trans is the return? the upper or lower?
Thanks in advance. I know there is tons of good knowledge here. Hoping for some help on my first post.
Second, why does the trans oil line run through the side of the radiator? Is that to heat fluid in winter or shed heat before going to the cooler? Which line coming out the passenger side of the trans is the return? the upper or lower?
Thanks in advance. I know there is tons of good knowledge here. Hoping for some help on my first post.
Senior Member
Joined: Mar 2000
Posts: 1,740
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From: SE Florida, USA
There is no heater for the transmission. There is a cooler in the radiator. It is a very effective transmission cooler.
I forget which is in and which is out of the trans. Follow the lines. The flow goes from the trans to the radiator cooler, then the aux cooler, then back to the trans.
The hole in the dipstick tube could be the source of your leak.
I forget which is in and which is out of the trans. Follow the lines. The flow goes from the trans to the radiator cooler, then the aux cooler, then back to the trans.
The hole in the dipstick tube could be the source of your leak.
Senior Member
Joined: Nov 2009
Posts: 825
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From: Virginia Beach
For the cooler, look at where the two lines to into the right side of the transmission. The one on the top is the return and the lower line is what send the fluid to the cooler. Just follow the lines as needed.
As far as the leak is concerned, don't overthink it. Wherever you see fluid is going to be where to look. If you have a hole in the dipstick tube, fix it. If that's the only suspicious area, use some engine degreaser and clean the trans and surrounding area after you fix the tube. If you see more fluid after driving, you'll have a better idea of where to look since you know it was clean before.
Regarding trans temperature, it would help if you posted the actual temperatures you're seeing. The transmission doesn't care about the ambient temperature. It does care about the fluid temperature though.
As far as the leak is concerned, don't overthink it. Wherever you see fluid is going to be where to look. If you have a hole in the dipstick tube, fix it. If that's the only suspicious area, use some engine degreaser and clean the trans and surrounding area after you fix the tube. If you see more fluid after driving, you'll have a better idea of where to look since you know it was clean before.
Regarding trans temperature, it would help if you posted the actual temperatures you're seeing. The transmission doesn't care about the ambient temperature. It does care about the fluid temperature though.