Dropping the transmission to change oil cooler line?

by 76malibu Sun Jun 11, 2017 4:04 pm

Hi guys,

A transmission oil cooler line on my 76 Malibu is broken and I cannot unscrew the fitting nuts on the transmission to change it.
Do I have to drop the transmission or do I miss a special tool? (see pictures below)

The wrenches I have cannot turn the nuts as they are in contact with the transmission tunnel.
I think the transmission is a TH350. The nuts are frozen in rust and the line is frozen in the nut.

If I have to drop the transmission I may have to unbolt part of the exhaust, crossmember, starter... and I try to avoid that extra work.

I don't want to patch the actual line as it may break again.
Any suggestions are welcome.
Thanks Smile

Dropping the transmission to change oil cooler line? Img_2011

Pic 1: view of the fitting nuts from the passenger side, between the catalytic converter and the frame
Dropping the transmission to change oil cooler line? Img_2012

Dropping the transmission to change oil cooler line? Img_2012

Pic 2: good view of the fitting nuts from underneath the transmission
Dropping the transmission to change oil cooler line? Img_2013

Pic 3: The set of wrenches I have. None have the clearance to unscrew the nuts
Dropping the transmission to change oil cooler line? Img_2014

Pic 4: the transmission tunnel don't allow the wrench to turn. The nuts are frozen in rust so I will strip them if I try to turn them in an angle or with the tip of the wrench

by Hawk03 Sun Jun 11, 2017 4:18 pm

I don't remember how tight it is in there or if this will work but can you try and cut the lines close to the nut and so you would be able to use a socket? If you're not going to reuse the line then destroying it shouldn't be an issue.

by Mcarlo77 Sun Jun 11, 2017 4:50 pm

I second that idea...why fight with those nuts?

by Joe73 Sun Jun 11, 2017 5:22 pm

Yes, I agree. Cut the lines and use a deep socket. Only other idea would be to borrow a crows foot flare wrench in the proper size. Its basically only the end part of the wrenches you show in your pic and you put a 3/8" extension into the end of it. So your using it at 90 degrees.
But cutting the line is the easiest and quickest.

by crice63 Sun Jun 11, 2017 5:56 pm

Even if you cut the lines to remove them you will need the crows foot to install the new lines. You may be able to unbolt the crossmember and mount, slide it back a bit and lower the trans an inch or two to open up space. This is all easier on a lift than jack stands. You don't want to cross thread those fittings going on.

by 76malibu Sun Jun 11, 2017 9:17 pm

Hawk03 wrote:I don't remember how tight it is in there or if this will work but can you try and cut the lines close to the nut and so you would be able to use a socket? If you're not going to reuse the line then destroying it shouldn't be an issue.

Thanks for the advice Hawk03.
It worked perfectly.

crice63 wrote:Even if you cut the lines to remove them you will need the crows foot to install the new lines. You may be able to unbolt the crossmember and mount, slide it back a bit and lower the trans an inch or two to open up space. This is all easier on a lift than jack stands. You don't want to cross thread those fittings going on.

You are right crice63. I will buy that tool:
Dropping the transmission to change oil cooler line? 41%2BMxQSyLkL

Dropping the transmission to change oil cooler line? Img_2016

Pic 1: Once the line cut, a breaker bar with extension fits well. The nut got loose without hassle.

Dropping the transmission to change oil cooler line? Img_2018

Dropping the transmission to change oil cooler line? Img_2018

Pic 2: The 1/2 flare nut was frozen solid to the 9/16 nut. You can see my previous attempt with the wrench. That could have ended as a stripped nut!

Dropping the transmission to change oil cooler line? Img_2015

Dropping the transmission to change oil cooler line? Img_2015

Pic 3: The only way to unmarry them is on the vise.

Dropping the transmission to change oil cooler line? Img_2017

Pic 4: I had to cut the line when it goes up to the radiator to be able to remove it. I have no idea how I can install a new one...

Maybe I should keep the new line straight then bend it once inside the engine compartment.

by pila Sun Jun 11, 2017 10:26 pm

Bending that line may be a problem with "kinks" in it, if you don't use a tubing bender. I would just get a new line made to fit, and bend it as needed to get it up in there....

by crice63 Mon Jun 12, 2017 1:51 am

Considering the price, quality, fitment, and good shipping reputation from Inline Tube, versus the dozen precise bends you'd have to make on your own, I'd at least take a look at their offerings before committing to do it myself. I bent some lines for my S10 and it is a pain. Kink the 10th bend and you start all over.

by Hawk03 Mon Jun 12, 2017 8:49 am

Glad you got the line off, little victories are sometimes the best. When I had everything together and started filling fluids I had a huge transmission leak at the fitting the transmission, the threads were stripped on the 9/16th nut. I think the transmission builder installed a used one because I don't remember it leaking that bad when I took everything apart. I'm sure I just used a regular wrench to tighten things up. Threading the new line through the engine compartment might be a 2 man job.

by Limey SE Mon Jun 12, 2017 9:57 am

I agree I would get the pre bent one and have a Buddy help you feed it thru there you will got thru one or two before you bend it right with no kinks I know I did

by Joe73 Tue Jun 13, 2017 11:33 am

https://www.summitracing.com/parts/sxt-9708 on sale $21

by Hs1973 Tue Jun 13, 2017 2:34 pm

You May have to remove the starter as the Lines go between the starter and the engine. There is a little metal bracket that sits on one of the oilpan bolts. Its a Real pain to get it sitting right with the starter in place. There can also be a problem getting the Lines past the motor mount, but Being 2 guys can help, or jacking the motor up and removing the mount is also a possibility.

Also make sure the fittings are sitting right in the treads, dont use any tools until you have made sure the fittings are going in right, otherwise the treads will strip and you are dead in the water. Worst case is a new radiator or trans.

by BBMALIBU Tue Jun 13, 2017 4:46 pm

I have a 1976 Malibu with a BBC and TH400, and I can get a wrench on those fittings with no problem.

When I did my trans lines, I bought bulk line and bent them myself (with tool).

All this was accomplished with trans, engine, and exhaust installed.

I'm just a little confused why you are not able to get a wrench on those fittings.

by 76malibu Wed Jun 14, 2017 10:11 pm

The bend that goes up to the radiator may make the job impossible without having to unbold components like the starter, exhaust, or even the engine.
A straight line can be reinstalled (with some patience).

After looking at a 1992 Chevy Silverado I noticed a rubber hose is used to plug an additional oil cooler, with fittings like that:
Dropping the transmission to change oil cooler line? 41Hn4e3uiCL

Dropping the transmission to change oil cooler line? 41Hn4e3uiCL

Dropping the transmission to change oil cooler line? 31GFq4JYfkL

The idea is then to do the bent part in rubber, which is quite close to current oil cooler lines:
Dropping the transmission to change oil cooler line? Rnb-625-101_ja_xl

Dropping the transmission to change oil cooler line? Rnb-625-101_ja_xl

by ant7377 Thu Jun 15, 2017 6:48 am

Make sure you use transmission cooler rubber line for any rubber section. Regular hose will burst.

by 76malibu Tue Jul 04, 2017 12:54 am

Well... doing the steel line part was not that bad after practicing the double flare technique. The trick when the pipe is slipping from the tool is to heat it with a propane torch (or buy another tool).

And reinstallation is somewhat easy when they are pre-bent like the original, except for the part coming up to the radiator which I plan to do with flexible hose.

Dropping the transmission to change oil cooler line? 19724010

Dropping the transmission to change oil cooler line? 19724010

The crowfoot flare nut wrench is mandatory to tighten that fitting.

by 76malibu Tue Jul 04, 2017 1:43 am

However, finding the right fittings to do the flexible hose part is a nightmare.
The short story is I have to do a conversion to NPT or AN.

The NPT conversion looks to be the cheapest, and the AN conversion looks to be the most professional.
What do you think?

The details:
I salvaged some fittings from a 92 Silverado, so the plan was to buy another set and put a rubber hose.
Unfortunately this is 1/4 NPS, which is not used anymore for pipe-to-flexible lines. We can find some for 5/16 NPS, like the Hayden 390, but none for 1/4 NPS.

Solution 1:
1/4 NPS male to 1/4 NPT male + 1/4 NPT female to 3/8 barb

Solution 2:
1/4 NPS male to AN-6 male + AN-6 female to AN hose (or to barb)

Also, finding rubber transmission hose that fits the barb can be hard. 3/8 hose is loose in the Silverado barbs (and should be snug). The auto part store hasn't 5/16 hose, and the guy told me that 11/32 hose does not exist...

The whole story is quite funny, as I had to go from Auto parts shops to Hydraulic shops, and every time the guy looked at me like I came from another planet because of this "weird" fitting they never saw before Very Happy

Dropping the transmission to change oil cooler line? 19807710

The 1/4 NPS - ?/? barb fittings from the 92 Silverado.

Dropping the transmission to change oil cooler line? 19749410

1/4 NPS is not 1/4 NPT.

Dropping the transmission to change oil cooler line? 19726910

A good view of the problem.

Dropping the transmission to change oil cooler line? 19749610

That NPT fitting is barely threaded in. One more turn and I may have to buy a new radiator.

by Joe73 Tue Jul 04, 2017 6:54 am

Couple questions here. Is the NPT fitting not going into the rad because the rad is Metric ? Just a thought.
Also, keep the barbs all the same size. No switching between 1/4, 5/16 or 3/8". Keep everything with the stock size diameter. You dont want to decrease diameter because that will INCREASE pressure but DECREASE flow.
I also would not be "heating" the tubing to get the double flare. It will make the metal brittle. Grab a better quality tool to do the job. If they are around you, Auto Zone and Advance Auto Parts loan tools for free.

by 76malibu Tue Jul 04, 2017 10:49 am

Joe73 wrote:Couple questions here. Is the NPT fitting not going into the rad because the rad is Metric ? Just a thought.

This radiator is 1/4 NPS like the original (also known as inverted flare). I tested it several times just to be sure I was not confused.
Dropping the transmission to change oil cooler line? 19718610

Dropping the transmission to change oil cooler line? 19718610

Joe73 wrote:Also, keep the barbs all the same size. No switching between 1/4, 5/16 or 3/8". Keep everything with the stock size diameter. You dont want to decrease diameter because that will INCREASE pressure but DECREASE flow.

You are right. The original steel tube is 5/16 so I have to use a bigger hose (3/8 or AN-6) because a 5/16 barb fitting has a constriction, I mean the 5/16 barb fitting internal diameter is smaller than 5/16. Fun fact, the 92 Silverado fitting has a constriction (5/16 = 0.3125).
Dropping the transmission to change oil cooler line? 19718710

Dropping the transmission to change oil cooler line? 19718710

by fasrnur Tue Jul 04, 2017 10:53 am

From what I see is that you're trying to go from inverted flare to NPT. The radiator is more than likely inverted flare and NTP just won't screw into it. Maybe something like this is what you need?

https://www.summitracing.com/parts/aer-fbm1211?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-aeroquip&gclid=CIrg1rjw79QCFQUNaQodRcMFeg

by 76malibu Tue Jul 04, 2017 11:16 am

fasrnur wrote:From what I see is that you're trying to go from inverted flare to NPT. The radiator is more than likely inverted flare and NTP just won't screw into it. Maybe something like this is what you need?

https://www.summitracing.com/parts/aer-fbm1211?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-aeroquip&gclid=CIrg1rjw79QCFQUNaQodRcMFeg

NPS to NPT (or AN) adapters that I see are all Male-to-Male. I think I should start with one of these then use a female-to-barb fitting after that.
https://www.summitracing.com/int/parts/fra-481670-bl
https://www.summitracing.com/int/parts/dvr-240006

by crice63 Tue Jul 04, 2017 1:33 pm

Barb fitting is overkill. Just flare the end of the tube, slide the hose over it and secure with a Hose clamp. My PO did that and I've been running it for over 2 years now. No leaks.

by BBMALIBU Tue Jul 04, 2017 1:49 pm

I used bulk steel tubing from trans to radiator.

But I used 2 sections of tubing for each line, connecting them with a union.

I used a longer length of tube from trans vs the section of tubing
connecting to radiator (cut and flare a section if needed).

Made it easier for bending at each end.

by Joe73 Tue Jul 04, 2017 1:49 pm

crice63 wrote:Barb fitting is overkill. Just flare the end of the tube, slide the hose over it and secure with a Hose clamp. My PO did that and I've been running it for over 2 years now. No leaks.

That is absolutely correct!! And if you dont want to flare it, just put 2 hose clamps on it. It wont come off, not enough pressure.

by fasrnur Tue Jul 04, 2017 3:46 pm

Very good point about just using the steel line, flaring the end and using hose clamps. We've all done it I'm sure with much success. I know I'm one of them. Very Happy

The one thing that might need to be added to this conversation is if you're going to use rubber line in any fashion on the trans lines, it would be wise to use transmission line and not gas line. Again, I'm guilty of using fuel line as I'm sure a lot of us have, but it can over time possibly go bad and cause one heck of a mess. lol

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