Transmission cooler lines

6

6cuda61

New member
Apr 17, 2020
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Anyone know if the trans cooler lines are unique to these coaches or if they come from something else? Mine are a bit suspect after a pin hole repair
yesterday.....normally i'd just make my own but i'm short on time before our major trip so if i can find something pre-made off another GM product it
would simplify things greatly.

Yes i know JimK has some and trust me i would love to give him more of my hard earned $$$ but between the shipping cost, shipping time and dollar
exchange its just not feasible at the moment.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
Rich,
The lines are unique to the coach. Even if there were other models that fit, finding those parts in stock here in Canada for something of this vintage will take some hunting and would most likely require shipping. Making your own lines and installing them is less than a day’s work. Get yourself the appropriate sized Poly-Armour Tubing and a bender and your halfway there.

Les Burt
Montreal
'75 Eleganza 26'

>
> Anyone know if the trans cooler lines are unique to these coaches or if they come from something else? Mine are a bit suspect after a pin hole repair
> yesterday.....normally i'd just make my own but i'm short on time before our major trip so if i can find something pre-made off another GM product it
> would simplify things greatly.
>
> Yes i know JimK has some and trust me i would love to give him more of my hard earned $$$ but between the shipping cost, shipping time and dollar
> exchange its just not feasible at the moment.
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
That's my plan if nothing is really available.....i've made hundreds of lines over the years for different vehicles and as you've said its not hard
just takes a few hours.

> Rich,
> The lines are unique to the coach. Even if there were other models that fit, finding those parts in stock here in Canada for something of this
> vintage will take some hunting and would most likely require shipping. Making your own lines and installing them is less than a day’s work. Get
> yourself the appropriate sized Poly-Armour Tubing and a bender and your halfway there.
>
> Les Burt
> Montreal
> '75 Eleganza 26'
>
>

> >
> > Anyone know if the trans cooler lines are unique to these coaches or if they come from something else? Mine are a bit suspect after a pin
> > hole repair
> > yesterday.....normally i'd just make my own but i'm short on time before our major trip so if i can find something pre-made off another GM
> > product it
> > would simplify things greatly.
> >
> > Yes i know JimK has some and trust me i would love to give him more of my hard earned $$$ but between the shipping cost, shipping time and
> > dollar
> > exchange its just not feasible at the moment.
> > --
> > Rich Mondor,
> >
> > Brockville, ON
> >
> > 77 Hughes 2600
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
A couple of companies make them but they are too long to ship. So they cut them in half. They are unique to the GMC so nothing else will fit. Make
your own. The are very low pressure return lines, so it is no big deal to bend and flare them.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Thanks Ken....i was more just trying to save a few hours work that i could use to other tasks on the coach seeing as how im working this week and next
but if nothing else crosses over the DIY is gonna be it [plus i hate it when they bend/cut lines to ship them].

> A couple of companies make them but they are too long to ship. So they cut them in half. They are unique to the GMC so nothing else will fit.
> Make your own. The are very low pressure return lines, so it is no big deal to bend and flare them.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
Keep in mind the connections at the tranny are not tapered pipe threads. Using that will probably crack the case. I think the connections were
inverted flare but don't remember for sure
--
Jerrod Winter
1977 Palm Beach
Green Jelly Bean
Twin Cities, Minnesota
 
Thanks for the heads up....i noticed when looking at the GMC sites that they supplied flare to threaded fittings for the trans so i knew something was
up

> Keep in mind the connections at the tranny are not tapered pipe threads. Using that will probably crack the case. I think the connections were
> inverted flare but don't remember for sure

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
What I remember is you buy tubing. Bend your own, but re-use the original old fittings on the new tubing.

You have two different size end pieces. The radiator side being an odd ball. (5/16” tube with what would be a 3/8” tube nut??

Some people think upping to 3/8” tube improves things. But that really takes some odd fittings to make work.


--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Jon—
It really doesn’t take any odd fittings to install 3/8” lines.

When I changed my lines years back to 3/8” I just bought standard 3/8” pre-flared steel brake lines. They are available in many different lengths.
I recall buying two fittings that would go into the top of my transmission. I ran lines from the transmission to the left frame rail and then joined another line to it with
a 3/8” inverted flare coupling. That is a very standard fitting, I ran a line connected to one of the frame lines behind the lower part of the radiator and they up to screw into the
transmission cooler in the radiator. I wanted to use an external transmission cooler which I mounted in front of the lower radiator. I bent another piece of brake line to go into
the other transmission cooler fitting in the radiator (the return line). This was bent to go around the side of the radiator and into the aux. cooler. Then I ran a line from the output
of the aux cooler to connect to the other line that ran along the frame rail.
So I used a total of 5 lengths of brake line, 2 fittings that went into the top of the transmission and 2 inverted flare couplers.
I bought a cheap tubing bender from Harbor Freight that worked very well with tight bends.
I did not need to do any flaring as the brake lines were already flared into new fittings.. All connections worked just fine with the 3/8” brake line fittings.
None of the fittings were odd sizes. The ones going into the transmission must be straight SAE thread fittings on one end going to an inverted flare on the other end.. DO NOT use pipe fittings which have a tapered thread. They have the
same threads per inch as the other fittings but the tapered portion could crack the casting of the aluminum transmission. Some transmissions do use the pipe thread but GM transmission do not. If you go to a radiator shop to buy
the fittings be careful as they might sell you the 3/8" tapered pipe thread fittings.

Emery Stora
77 Kingsley
Frederick, CO

>
> What I remember is you buy tubing. Bend your own, but re-use the original old fittings on the new tubing.
>
> You have two different size end pieces. The radiator side being an odd ball. (5/16” tube with what would be a 3/8” tube nut??
>
> Some people think upping to 3/8” tube improves things. But that really takes some odd fittings to make work.
>
>
>
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
You maybe correct. I just thought I distinctly gave up on changing tranny lines after a day driving around town looking at all the auto parts stores
and hardware stores, and re-used my old lines when I did my drivetrain rebuilds. Those tranny lines put me back a full day on the project.

I was thinking the fittings on tranny are smaller flare nut wrench then the radiator side. And to find the different nuts to match similar tube size
was a problem.

But that was going on two years ago when I tried and failed at that.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
I went to 3/8 brake line tubing for the trans cooler. One of the things I observed is that the couplers and adaptors that we use to complete that job
of hooking those multiple pieces together is, the hole in the couplers/adaptors is about the same ID as 5/16 brake line tubing. What is the point in
running 3/8 line if you are restricting flow down to 5/16 at each of the couplers? So, I fit a drill that was same ID as the 3/8 tube, and used the
drill to enlarge the hole in the couplers/adaptors to the same ID as the tubing. Had to clamp the couplers/adaptors in a drill press vice to get the
hole centered and straight, but actually a fairly easy thing to do to make the flow up to the 3/8 capability. JWID
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
Oh, the other thing I did is move the path of the cooler line from the driver side frame rail and across the front of the radiator, moved to over the
top of the transmission bell housing to the passenger side frame rail. Then straight down to the radiator for a direct straight in fit. This then
allowed me to put a coupler at the top of the transmission bell housing, so that when I needed to remove the trans, it was easier to disconnect the
couplers at the top of the trans than reaching down to the trans cooler line inputs. JWID
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
I used premade lengths from Advanced - it took two of their longest, plus a short one and coupling to get to the upper cooler outletfor the
transmission. Bending tool is cheap from Freight, harbor...

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
 
Larry i like that idea and it gets it away from the exhaust manifold as well.

> Oh, the other thing I did is move the path of the cooler line from the driver side frame rail and across the front of the radiator, moved to over
> the top of the transmission bell housing to the passenger side frame rail. Then straight down to the radiator for a direct straight in fit. This
> then allowed me to put a coupler at the top of the transmission bell housing, so that when I needed to remove the trans, it was easier to disconnect
> the couplers at the top of the trans than reaching down to the trans cooler line inputs. JWID

--
Rich Mondor,

Brockville, ON

77 Hughes 2600
 
Thanks Larry. Turnquist suggested I should up my tranny cooler lines to 3/8”. So hoping I have better luck with fittings. I will be not
reusing the radiator tranny cooler and will be installing a larger one i front of radiator.

When I tried to re-route and go to 3/8” line. I found the space on my 455 from passenger frame rail
To the exhaust header to be damn near the same distance as the stock lines were
To the drivers header. I opted to wrap the lines in an insulations shield at that
Time.

I am thinking 3/8” hardlines following the same route as stock. Then transition to AN fittings and a flexible hose right at the support off the
fan shroud.

Turnquist said I need to make sure the cooler has the larger ports.

Always a project.
--
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Jan
I have not seen the need for flexible hose. The steel lines seem to have plenty of flex and I have had them in for several years with no problem.

Emery Stora

>
> Thanks Larry. Turnquist suggested I should up my tranny cooler lines to 3/8”. So hoping I have better luck with fittings. I will be not
> reusing the radiator tranny cooler and will be installing a larger one i front of radiator.
>
> When I tried to re-route and go to 3/8” line. I found the space on my 455 from passenger frame rail
> To the exhaust header to be damn near the same distance as the stock lines were
> To the drivers header. I opted to wrap the lines in an insulations shield at that
> Time.
>
> I am thinking 3/8” hardlines following the same route as stock. Then transition to AN fittings and a flexible hose right at the support off the
> fan shroud.
>
> Turnquist said I need to make sure the cooler has the larger ports.
>
> Always a project.
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
I up sized my transmission line to all 3/8” on our first coach. See Album

http://www.gmcmhphotos.com/photos/g3670-transmission-line-26amp-3b-filter.html

On the stretch I use hydraulic hose made up lines which work. You do need the adapters to go up to 3/8” out/in of the transmission.m mJim K has had them in the past and he can tell you what and where you can get them, if he no longer carries them.

JR Wright
Michigan

>
> Thanks Larry. Turnquist suggested I should up my tranny cooler lines to 3/8”. So hoping I have better luck with fittings. I will be not
> reusing the radiator tranny cooler and will be installing a larger one i front of radiator.
>
> When I tried to re-route and go to 3/8” line. I found the space on my 455 from passenger frame rail
> To the exhaust header to be damn near the same distance as the stock lines were
> To the drivers header. I opted to wrap the lines in an insulations shield at that
> Time.
>
> I am thinking 3/8” hardlines following the same route as stock. Then transition to AN fittings and a flexible hose right at the support off the
> fan shroud.
>
> Turnquist said I need to make sure the cooler has the larger ports.
>
> Always a project.
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
IIRC, the only electrical connection to the radiator is through the trans lines. If you use flex connections like rubber trans hose, you may loose
that grounding and have issues with electrolysis and corrosion in the radiator. Make sure you have some kind of grounding to the radiator. Someone
please correct me if I am wrong about this.
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
> Thanks Larry. Turnquist suggested I should up my tranny cooler lines to 3/8”. So hoping I have better luck with fittings. I will be not
> reusing the radiator tranny cooler and will be installing a larger one i front of radiator.
>
> When I tried to re-route and go to 3/8” line. I found the space on my 455 from passenger frame rail
> To the exhaust header to be damn near the same distance as the stock lines were
> To the drivers header. I opted to wrap the lines in an insulations shield at that
> Time.
>
> I am thinking 3/8” hardlines following the same route as stock. Then transition to AN fittings and a flexible hose right at the support off
> the fan shroud.
>
> Turnquist said I need to make sure the cooler has the larger ports.
>
> Always a project.

John,
If Steve doesn't have the fittings for the transmission to convert to 3/8 lines, I THINK I might have a set of them. let me know, I could mail them to
you.

--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
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