Transmission oil line: steel or rubber?

H

heinz wittenbecher

New member
Mar 1, 1998
1,470
0
0
I realize that our GMC's have with metal ( I assume steel ) lines from
tranny to radiator-tranny cooler.

I'm going to be installing an external tranny fluid filter and a new cooler
tomorrow and am trying to decide what to do re tranny lines.
Transmission cooler kits come with rubber ( tho be it hi temp rubber ) hose
to use. Rubber was also used to join metal to hose fitting at my last tranny
change/cooler install.

While steel has the obvious longevity, it can also be a pain.

I'm wondering if anyone has any rubber hose of length currently in use or
had in use and changed back to steel due to failure.

I'm not concerned about longevity as I would not have a problem to change it
out every few years, just concerned with drastic failures in less than 2
years or so.

Also... any thought on whether an external filter would increase back
pressure on the tranny itself in an undesirable manner? I know that the
catalogs tout "improvement and longer tranny life", but they sell this
stuff. I'm looking for some first hand exposure... pro or con.

TIA - Heinz

P.S. Still undecided on whether to use the termostat. It's fixed at 185
degrees +/- 10 degrees. Still looking for one that's adjustable.
 
>
> While steel has the obvious longevity, it can also be a pain.
>
> I'm wondering if anyone has any rubber hose of length currently in use or
> had in use and changed back to steel due to failure.

Heinz,

My transmission fluid lines were badly rusted and I replaced them with
SS lines from Classic Tube. They were kinda' pricey($200 IIRC)
considering that, with some patience and a good tubing bender you could
make them yourself for 1/2 the price including tools. I haven't added
an external cooler, but always thought if I did, I would break the
return line from the radiator where it "els" up and put AN flares on
both ends. Then have "Aeroquip" lines made up to connect the SS lines
to the cooler. If you can't find a cooler with AN flares, most racer
shops sell braze-on AN flares(Racer Wholesale has them in their
catalog). Also, I would probably install a bypass thermostat to prevent
the trans from running too cool - althought I remember some traffic here
recently that implied this is not *really* a problem.

My $.02 YMMV,
Patrick
- --
Patrick Flowers
Mailto:patrick

The GMC Motorhome Page
http://www.gmcmotorhome.com
 
Speaking of these lines, which one is the return line?

Richard
>
> >
> > I'm wondering if anyone has any rubber hose of length currently in use or
> > had in use and changed back to steel due to failure.
> >
> > I'm not concerned about longevity as I would not have a problem to change
> it
> > out every few years, just concerned with drastic failures in less than 2
> > years or so.
> >
> > Also... any thought on whether an external filter would increase back
> > pressure on the tranny itself in an undesirable manner?
> Heinz,
> I used the rubber connectors on the steel lines, 10,000 miles, no problems,
> tranny has not run over 190* since I replaced cooler & fan clutch (both
> Hayden) and added filter & temp gauge. Jim Bounds suggested installing the
> temp sensor in return line from rad to tranny, but I'm glad I insisted in
> measuring direct from tranny output before cooled by rad & cooler.
> Lanier
>
 
> Heinz,
> I used the rubber connectors on the steel lines, 10,000 miles, no
problems,
> tranny has not run over 190* since I replaced cooler & fan clutch (both
> Hayden) and added filter & temp gauge. Jim Bounds suggested installing the
> temp sensor in return line from rad to tranny, but I'm glad I insisted in
> measuring direct from tranny output before cooled by rad & cooler.
> Lanier
>
>

Lanier,
Is the temp always (or nearly always) at 190 or over coming out of the
tranny?

I'm considering adding a thermostat control, but it's fixed at 180 deg +/1
10 deg and I'm concerned it's too high and would never make it through the
cooler in regular running.

You can set my mind at ease if your temp is indeed always, or mostly, above
that.

TIA - Heinz
 
>
> > I'm considering adding a thermostat control, but it's fixed at 180 deg
+/1
> > 10 deg and I'm concerned it's too high and would never make it through
the
> > cooler in regular running.
>
> Heinz,
> If in fact your transmission fluid never exceeds 190 deg. F, then
there's
> really no need to send it through the cooler. If it never reaches 180
deg.F,
> then you really should warm it up a little. (Like by sending it through
the
> radiator-mounted oil cooler, though I recall you had a problem with yours,
so
> maybe you can't.)
> Bottom line is: go ahead and use the fixed thermostat. It was designed
> for automatic transmissions, like ours. 180 deg.F +/- 10 deg is a long
way
> from overheating your fluid.
> My .02.
>
> Rick Staples

Thanks for your post Rick.

That's pretty well what I ended up doing, as a start anyway. I'll have a
temp gauge in the filter and my normal for the pan so I'll have an idea of
in and "at rest" in the pan. Eventually I'll add the tran filter sensor to
the AV10, but I need to wait until they have more inputs available for me.

Didn't get finished today as I ran into trouble with the caliper I bought.
Typical rebuild quality control. Couldn't seal the brakeline connectection
due to nicks that the gasket washer couldn't handle. (Fenco Rebuild).

I'm planning to cut the existing steel lines about even with front of engine
and then go rubber transmission oil cooler type hose. The filter got mounted
in the forward corner of the frame. Pics upon completion (and after I find
my battery charger for the camera :-).

Heinz
 
I'm trying to confirm that the previous owner hooked up the external
transmission oil cooler correctly.

Does this sound correct?

- -Steel line from the transmission enters the O.E. built-in cooler at its lower
connection.
- -Line from the upper connection of the O.E. cooler goes to the add-on cooler and
enters it at the higher connector.
- -Line exits the add-on cooler from the lowermost connection and returns to the
transmission.

I note that the transmission fluid enters the O.E. built-in cooler at the bottom
and exits the top and wonder if, likewise, it should enter the add-on cooler at
the bottom and exit the top. Or doesn't it matter?

Richard
 
>
> Is the temp always (or nearly always) at 190 or over coming out of the
> tranny?
> >>
> Heinz,
> Once it warms up, it hangs just on the left edge of the 190 mark and I'd
have
> to do some seious hill-climbing to get much over that.
> Lanier
>
That sounds excellent.
That means it normally leaves the tranny at 180/190 and the thermostat in
line with the tranny cooler will help me keep it there.

Thanks again

Heinz
 
>.... but I'm glad I insisted in
>measuring direct from tranny output before cooled by rad & cooler.

I am thinking about installing one in the output line too. Would you check
and tell me which line contains the fluid flowing out of the transmission?

TIA,
Dave
73 Sequoia
 
All the trannies I have seen, (not a lot) the oil comes from the trans into the top
of the rad-out the bottom of the rad into the aux. cooler(top) out of the aux.
cooler- into the return line which used to be the lower line off of your rad.

> I'm trying to confirm that the previous owner hooked up the external
> transmission oil cooler correctly.
>
> Does this sound correct?
>
> -Steel line from the transmission enters the O.E. built-in cooler at its lower
> connection.
> -Line from the upper connection of the O.E. cooler goes to the add-on cooler and
> enters it at the higher connector.
> -Line exits the add-on cooler from the lowermost connection and returns to the
> transmission.
>
> I note that the transmission fluid enters the O.E. built-in cooler at the bottom
> and exits the top and wonder if, likewise, it should enter the add-on cooler at
> the bottom and exit the top. Or doesn't it matter?
>
> Richard
 
I'm just doing tranny lines.

The bottom of rad is "from tranny" in my 455 Transmode.

To find out for sure: disconnect, unplug coil so that engine can't start,
put a ziplock or other plastic bag over the end of the pipe and crank
starter. It indeed "from", tranny fluid will be in the bag. It took several
cranks on mine. (Wanted to be sure we had the right line going to new
external filter).

Heinz
...back to the store for another brass fitting. cheech.

> All the trannies I have seen, (not a lot) the oil comes from the trans
into the top
> of the rad-out the bottom of the rad into the aux. cooler(top) out of the
aux.
> cooler- into the return line which used to be the lower line off of your
rad.
>

>
> > I'm trying to confirm that the previous owner hooked up the external
> > transmission oil cooler correctly.
> >
> > Does this sound correct?
> >
> > -Steel line from the transmission enters the O.E. built-in cooler at its
lower
> > connection.
> > -Line from the upper connection of the O.E. cooler goes to the add-on
cooler and
> > enters it at the higher connector.
> > -Line exits the add-on cooler from the lowermost connection and returns
to the
> > transmission.
> >
> > I note that the transmission fluid enters the O.E. built-in cooler at
the bottom
> > and exits the top and wonder if, likewise, it should enter the add-on
cooler at
> > the bottom and exit the top. Or doesn't it matter?
> >
> > Richard
>
>
 
You must log in or register to reply here.
GMCMI Fall 2026 Rally
Get your shine on at www.cruzingear.co

Share this page

Share this page
Top Bottom
Back