Overheat/timing adj.

[larry dtimothy]

> If the radiator system is functioning properly it will never overheat.

Now that's what I like to hear! Should that be true when I'm towing
5,000+ lbs
up a long mountain climb?

Tom Wrote:
>Wouldn't it be simpler and cheaper to buy the Caspro system that
> automatically detects spark knock and retards the spark instead of trying to
> do it manually?

I missed the reference to manual timing adjustment, where was that? I do
plan to use the Caspro automatic.

Tim Timothy
73 Glacier NW FL

 

[thomas g. warner]

The answer of course is that the GMC was only designed to trailer no more
than 1000# as manufactured. You are asking a 20 year old coach to perform
like one designed for towing. The heat for the most part that you are
contending with going up that hill is that from the Torque
converter(assuming that you don't really get on the gas and try to race up
the hill). The more it slips the more heat is given off. There are some
things we can do:

1. Install a heavy duty 2 speed torque converter (caspro has one model)
2. Install a vacuum gauge and use it when hauling heavy loads up hill.
3. Install wetting agents in the water to reduce the temperature
4. Install a large transmission oil cooler and get it out of the engine
radiator(it is the major cause of engine overheating when going up hills)
5. Install a transmission and engine oil temp gauges
6. Install the 3.46 or higher final drive
7. Reduce the exhaust restrictions
8. switch to synthetic oils in the engine, tranny and final drive
9. When rebuilding the tranny use heavy duty parts. They increase friction
and reduce temperatures
10. Ensure that the timing is set correctly (I intend to install a spark
knock detector and ignition retarder similar to Caspros)

>> If the radiator system is functioning properly it will never overheat.
>
>Now that's what I like to hear! Should that be true when I'm towing
>5,000+ lbs
>up a long mountain climb?
>
>Tom Wrote:
>>Wouldn't it be simpler and cheaper to buy the Caspro system that
>> automatically detects spark knock and retards the spark instead of trying to
>> do it manually?
>
>I missed the reference to manual timing adjustment, where was that? I do
>plan to use the Caspro automatic.
>
>Tim Timothy
>73 Glacier NW FL
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach

 

[zachary zehnacker]

Tom,

While I agree that most of these solutions are good ones, I have some
comments about some of them.

>1. Install a heavy duty 2 speed torque converter (caspro has one model)

In the high stall mode, the converter builds up even more heat. Caspro's
fuzzy logic even uses timers to ensure that you don't stay in the high
stall mode for too long to try and keep the trans cooler. I think that
this solution just moves the heat problem somewhere else if it helps the
motor at all.

>2. Install a vacuum gauge and use it when hauling heavy loads up hill.

This is a good idea, and will prompt the driver to downshift at the
appropriate times.

>3. Install wetting agents in the water to reduce the temperature

I have heard of good results with these, but do not have personal
experience with them. Most seem to say that too much antifreeze negates a
lot of their effectiveness though. They are said to actually increase the
temperature of the water, because they are able to draw more heat out of
the block. This makes the improvements hard to quantify because most water
temp gauges will actually go up even though the block temp is probably
cooler than it would have been without the additives.

>4. Install a large transmission oil cooler and get it out of the engine
>radiator(it is the major cause of engine overheating when going up hills)

This is a very good idea. We have actually installed two coolers in front
of the radiator on ours. Our fluid in the pan is now very cool. We still
run the fluid through the radiator. Our fluid is FAR below 195, so it
should actually be cooling the water. We used to have it go through the
coolers after the radiator, but now we put it though the coolers first and
then the radiator because we felt that the fluid was actually too cold by
the time it got to the trans the other way.

>5. Install a transmission and engine oil temp gauges

Another good idea. We were happily surprised to find out our trans ran
MUCH cooler than we expected. We don't have an oil temp gauge because we
are pretty much out of spots to put one cleanly, but it would also be a
worthwhile addition.

>6. Install the 3.46 or higher final drive

I still don't think the higher final drives are worth the money, but you
are correct saying that they should help with overheating. I still think
that downshifting when appropriate is the better solution though. I'll
hype the downshift button again for this purpose. We really like the
button we added which simulates full throttle to the trans even when you
are not at full throttle. The trans downshifts when you press the button
and stays there as long as you hold the button. It is much more convenient
and much safer (no chance of shifting into reverse or park) than
downshifting with the stalk.

>7. Reduce the exhaust restrictions

Changing from Dynomax mufflers to Edelbrock mufflers made a very big
difference in engine compartment heat (and probably engine heat as well).
The starter would have heat soak problems with the Dynomax mufflers, but
was fine once we changed to the Edelbrocks.

>8. switch to synthetic oils in the engine, tranny and final drive

Another good idea. We have changed over to synthetic in the engine. We
have found that we use less oil per stop now than we did with the regular
oil (fresh engine so YMMV). We have also changed over the final drive to
synthetic. The trans fluid is something we would like to do. It seems to
be pretty expensive though. We are also currently running Type-F (after a
complete rebuild to avoid compatibility problems) in the trans which would
limit us to Redline. We will probably do it the next time we change the
trans (probably this winter) and go with the Mobil One DexIII fluid. We
like to keep our trans fairly fresh because of the towing and distances we
travel with the trailer. We have two so one is always ready to go in. We
usually swap them about every 3 years or so at around 45,000 miles. This
is probably not necessary, but we feel safer about it.

>9. When rebuilding the tranny use heavy duty parts. They increase friction
>and reduce temperatures

We have our transmissions done by our race trans shop, so they add the same
components they would for a race trans. The rebuilt transmissions don't
seem to be any better or any worse than the original stock trans, however,
which I'm led to believe is pretty much a stock Toronado trans. Was the
original GMC trans "beefed" up when compared to the Toronado trans?

>10. Ensure that the timing is set correctly (I intend to install a spark
>knock detector and ignition retarder similar to Caspros)

Another good idea. We used the MSD timing control to manually adjust our
timing while traveling. We have since switched to fuel injection with a
knock sensor. The system controls all the timing so we don't have to worry
about it anymore (VERY NICE!). The Caspro unit sounds like it would have
similar qualities to the EFI system's timing controls which would probably
make it a very good addition to a GMC. We once had to travel with no
advance whatsoever because of an ignition module failure and the engine
temperature was much higher than normal.

Just some of our experiences,

Zak

 

[thomas g. warner]

Zak as far as I know the GMC tranny is the same as the Toro. Final drive is
the same also and the 3.07 is in fact the towing drive for the Toro.

>From talking to an experienced tranny friend of mine, he says there are
heavy duty parts available for the TH-425 transmission. I am trying to make
a list of them. Do you know of any?

With reference to the wetting agents. They also provide a more uniform temp
of the block and eliminate any possible hot spots.

The Caspro knock sensor that I am considering automatically retards and
advances the timing.

Did you also install the 3" pipes?

>Tom,
>
> While I agree that most of these solutions are good ones, I have some
>comments about some of them.
>
>>1. Install a heavy duty 2 speed torque converter (caspro has one model)
>
>In the high stall mode, the converter builds up even more heat. Caspro's
>fuzzy logic even uses timers to ensure that you don't stay in the high
>stall mode for too long to try and keep the trans cooler. I think that
>this solution just moves the heat problem somewhere else if it helps the
>motor at all.
>
>>2. Install a vacuum gauge and use it when hauling heavy loads up hill.
>
>This is a good idea, and will prompt the driver to downshift at the
>appropriate times.
>
>>3. Install wetting agents in the water to reduce the temperature
>
>I have heard of good results with these, but do not have personal
>experience with them. Most seem to say that too much antifreeze negates a
>lot of their effectiveness though. They are said to actually increase the
>temperature of the water, because they are able to draw more heat out of
>the block. This makes the improvements hard to quantify because most water
>temp gauges will actually go up even though the block temp is probably
>cooler than it would have been without the additives.
>
>>4. Install a large transmission oil cooler and get it out of the engine
>>radiator(it is the major cause of engine overheating when going up hills)
>
>This is a very good idea. We have actually installed two coolers in front
>of the radiator on ours. Our fluid in the pan is now very cool. We still
>run the fluid through the radiator. Our fluid is FAR below 195, so it
>should actually be cooling the water. We used to have it go through the
>coolers after the radiator, but now we put it though the coolers first and
>then the radiator because we felt that the fluid was actually too cold by
>the time it got to the trans the other way.
>
>>5. Install a transmission and engine oil temp gauges
>
>Another good idea. We were happily surprised to find out our trans ran
>MUCH cooler than we expected. We don't have an oil temp gauge because we
>are pretty much out of spots to put one cleanly, but it would also be a
>worthwhile addition.
>
>>6. Install the 3.46 or higher final drive
>
>I still don't think the higher final drives are worth the money, but you
>are correct saying that they should help with overheating. I still think
>that downshifting when appropriate is the better solution though. I'll
>hype the downshift button again for this purpose. We really like the
>button we added which simulates full throttle to the trans even when you
>are not at full throttle. The trans downshifts when you press the button
>and stays there as long as you hold the button. It is much more convenient
>and much safer (no chance of shifting into reverse or park) than
>downshifting with the stalk.
>
>>7. Reduce the exhaust restrictions
>
>Changing from Dynomax mufflers to Edelbrock mufflers made a very big
>difference in engine compartment heat (and probably engine heat as well).
>The starter would have heat soak problems with the Dynomax mufflers, but
>was fine once we changed to the Edelbrocks.
>
>>8. switch to synthetic oils in the engine, tranny and final drive
>
>Another good idea. We have changed over to synthetic in the engine. We
>have found that we use less oil per stop now than we did with the regular
>oil (fresh engine so YMMV). We have also changed over the final drive to
>synthetic. The trans fluid is something we would like to do. It seems to
>be pretty expensive though. We are also currently running Type-F (after a
>complete rebuild to avoid compatibility problems) in the trans which would
>limit us to Redline. We will probably do it the next time we change the
>trans (probably this winter) and go with the Mobil One DexIII fluid. We
>like to keep our trans fairly fresh because of the towing and distances we
>travel with the trailer. We have two so one is always ready to go in. We
>usually swap them about every 3 years or so at around 45,000 miles. This
>is probably not necessary, but we feel safer about it.
>
>
>>9. When rebuilding the tranny use heavy duty parts. They increase friction
>>and reduce temperatures
>
>We have our transmissions done by our race trans shop, so they add the same
>components they would for a race trans. The rebuilt transmissions don't
>seem to be any better or any worse than the original stock trans, however,
>which I'm led to believe is pretty much a stock Toronado trans. Was the
>original GMC trans "beefed" up when compared to the Toronado trans?
>
>>10. Ensure that the timing is set correctly (I intend to install a spark
>>knock detector and ignition retarder similar to Caspros)
>
>Another good idea. We used the MSD timing control to manually adjust our
>timing while traveling. We have since switched to fuel injection with a
>knock sensor. The system controls all the timing so we don't have to worry
>about it anymore (VERY NICE!). The Caspro unit sounds like it would have
>similar qualities to the EFI system's timing controls which would probably
>make it a very good addition to a GMC. We once had to travel with no
>advance whatsoever because of an ignition module failure and the engine
>temperature was much higher than normal.
>
>
>Just some of our experiences,
>
> Zak
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach

 

[zachary zehnacker]

Tom,

I'm not exactly sure what upgraded parts our trans shop puts in. I know
the converters have the anti-balloon support and furnace brazed fins. The
transmissions in our race cars use kevlar bands, but I don't know whether
these go in the motorhome trans or not. There might be some heavy duty
clutches as well. Besides the bands and the clutches, I don't think there
is much else to upgrade in a trans. I think most problems with rebuilt
transmissions are usually due to the rebuilder and not really the parts
they use. GMCers seem to get good service from the original stock trans
and then begin to have trouble once they get it rebuilt. Since the
original parts were no better than the Toronado parts, a rebuild to
Toronado specs should give the same service as the original trans, but this
does not seem to be the case with a lot of rebuilders.

The Caspro knock sensor/timing control sounds pretty interesting. We had
always considered it, but never went for it. Now we have the EFI which
basically does the same thing. If you do decide to go for it, please let
us all know how it works.

We did install the 3" pipes along with the headers. It was a complete
system from one of the GMCMM suppliers. It originally came with Dynomax
mufflers, but we had some problems with them blowing out. They would
actually pulse at idle. We then switched to Flowmasters. They were built
like tanks, but were much too loud for our tastes. Others have reported
their Flowmasters are quiet enough, so there may be another version that
would have been better suited for the GMC than the ones we tried. We
actually went back to the Dynomax mufflers because we couldn't stand the
noise from the Flowmasters. Last spring, we switched to Edelbrock
stainless mufflers. We have been very pleased with these mufflers. They
are made from thick stainless steel, seem very free flowing, and seem to be
quieter than even the Dynomax mufflers. These should also last a long time.

I'm not sure that I would recommend the headers and 3" exhaust to anyone
that is not towing. The system did seem to improve power, and may have
helped the towing mileage a little, but the non-towing mileage actually
seemed to go down a little after we installed the system. The motorhome,
even with the new mufflers, is not as quiet as it was with the stock
system. With the stock system, you could not hear anything when in the
back of the motorhome, and the engine was also almost silent even sitting
right above it.

Zak

>Zak as far as I know the GMC tranny is the same as the Toro. Final drive is
>the same also and the 3.07 is in fact the towing drive for the Toro.
>
>From talking to an experienced tranny friend of mine, he says there are
>heavy duty parts available for the TH-425 transmission. I am trying to make
>a list of them. Do you know of any?
>
>With reference to the wetting agents. They also provide a more uniform temp
>of the block and eliminate any possible hot spots.
>
>The Caspro knock sensor that I am considering automatically retards and
>advances the timing.
>
>Did you also install the 3" pipes?

>Tom & Marg Warner
>Vernon Center NY
>1976 palmbeach
>
>