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Old 05-25-2020, 12:26 PM
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Default TH 400 cooler line replacement

I'm replacing the cooler lines on my TH400 transmission (67 GTO) and thought I'd check on any difficulties in advance. I can see that it's tough to gain access to undo the lines at the transmission. I can get to the bottom line, but it appears that I must remove the dipstick tube to access the upper line.

Will I have a face full of fluid when I remove the dipstick tube? In the past I've just capped the lines at the radiator when removing them, so I don't know how much will leak out when I remove the lines at the transmission.

I'm pretty sure I'll need to replace the O-ring at the bottom of the dipstick tube; does anyone know if this a standard size that I can get at a hardware store?

Thanks in advance.

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Old 05-26-2020, 03:12 PM
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Lacking any heads-up, I went ahead with this job. For those doing this in the future, yes, a bit more than a pint of transmission fluid will come out when removing the dipstick tube, with the car on ramps. Mine had the o-ring and also some black RTV above that (I assume it leaked in the past, but it hasn't been leaking). It's easy to do without making much of a mess.

After removing the tube, the cooler lines are "easier" to reach, but not much. There still isn't much room to reach the upper line and get a line wrench to turn. Removing the lower line, which is a tad easier, provides more room for the upper.

Only a trivial amount of fluid came out when I removed the lower line. Now to remove it and install the new one...and find a new O-ring for the tube.

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Old 05-26-2020, 03:32 PM
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fyrffytr1 fyrffytr1 is offline
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Just curious, why did you decide to replace the lines?

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Old 05-27-2020, 09:34 AM
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Reasonable question, it would have been very easy to leave everything alone. My existing original lines were rusty, corroded, and bent, and it wasn't easy to use the hold-down clip on the passenger side (the lines are not even close to the right place where the clip is). The filler tube was quite rusty, but it looks like new after wire brushing. I bought the new lines a few years ago when I recored my original Harrison radiator. It looked so good that I thought new lines would be a nice addition. My local radiator shop charged me $200 to do the recore!

I imagine that many of us have gotten to the point where we are trying to make every little part "just right", especially lately. So it's just a bit of "attention to detail" (my wife has another word for it). After all these years, I still have trouble learning "if it ain't broke, don't fix it".

BTW, the filler tube O-ring is listed as #1164253 in the assembly manual. This number has been discontinued and the new GM part # is 6264902. Felpro 411 is one of many equivalents. I can still get the GM part from my local dealer, but I have to order 20 at $2.60 ea. I found them at NAPA and Advance.

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Old 05-29-2020, 11:03 AM
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Default Cooler line clip location, bolt size

I've gotten the cooler lines replaced, but I am not positive about the location of the clip that holds the line above the right control arm. I can't make sense of the Assembly Manual figures for this. I see a reasonably large hole in about the right place.

Does anyone have a good photo showing the location? It would also be great to know the bolt size and type. Am I correct that it's a self-tapping automotive bolt?

Thanks.

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Old 05-29-2020, 11:58 AM
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I'd be curious to know this info, too, as I'll have to replace those lines on my car as well. Old ones were beat up and worn out from being unsecured and rubbing on everything, including the steering centerlink.

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Old 05-29-2020, 01:17 PM
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I'll bet ni-cop would work great for this

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