A bud of mine just had a 400 turbo-hydromatic manual valve body built for his '78 Camaro 427c.i. bored/stroke roots blower car. He has 3.50:1 gears and "pullied-up" on the blower. His temp. gauge on the fluid line out of the tranny indicated 250*F after a 1/4 mile street run full throttle. He never used the 250 shot as of this date, and asked me to post this question:
What is the max. fluid temp. that is acceptable without harming his new tranny build, and secondly, would synthetic tranny fluid do any good with heat reduction? He already has an inline additional cooler (37k btu) with an separate electric fan on the set-up...
Any other suggestions to keep his tranny in top trim?...

 

Max allowable temp is a function of the fluid. The heat doesn't so much harm the tranny directly, but it harms the fluid, which in turns causes accelerated transmission wear and improper operation. Absolutely he should use a synthetic fluid. With a good synthetic the tranny may run cooler, but more to the point it will still lubricate properly at high temps. With a good synthetic, I wouldn't worry about 250 degrees if it operates properly and a good synthetic is used.

Just IMHO. I am not an auto tranny expert, hopefully some who are will chime in.

Rich Krause

 

Listen to Rich.

250 F after one 1/4 mile run sounds high to me. Torque converter slippage generates the lion's share of the heat. If he has a very high stall converter and did a number of consecutive hard starts or burn outs I could see the high temp. Did it come right back down when cruising?

I'd try to keep the fluid under 250 if it were my car.

 

I know that there is a classic tech but no specific transmission section on this board. When I posted the original question, I had returned home from a long day. Let me now explain what's going on.
The tranmission shop is extending a warranty on the tranny for a year. The builder is very confident with his work. He suggested installing the gauge to monitor the fluid temp (told him that the tranny fluid temp. should be appx. that of the coolant in the radiator) , but never suggested using synthetic (actually I think he doesn't ever suggest it). I would think that in a full 1/4 mile run situation, the tranny fluid would get hotter than the coolant in the radiator. Would this be the case?
Is there "something" about synthetic tranny fluid that is counterproductive to a transmission under severe use. My thoughts is that it would be just the opposite, that the tranny fluid being synthetic would be superior to standard tranny fluid.
My bud also went with the aluminum finned tranny pan with an extra two quart capacity. He's a bit worried about the fluid temp. b/c his last vehice (vette) experienced tranny problems due to high abuse (i.e. drag racing).
Sorry for being so long, and thanks Rich for the reply...
He has a P.I. 3800 stall and full time manual shift valve body.

 

Given what I wrote above, and given that the N2O hasn't been added to the equation as of yet (which will probably bring the fluid temp. up even higher) what else can be done (and what is your opinion about switching to a full synthetic tranny fluid)? He really doesn't want to go against the tranny builder and go with synthetic behind his back, but he feels he has to keep the fluid temp. as low as possible. And the high temp. did come back down after the run pretty quickly...

 

The synthetic may operate at a lower temp due to higher heat conductivity (which is easier to "design in" with a synthetic).

Otherwise, here are options for lowering the temp:

1. tighter (lower) stall
2. better/larger cooler
3. larger capacity finned aluminum pan (which will provide a larger heat sink and better heat transfer).

If I saw 250 degrees I would definitely want synthetic in there though. Carl Rossler and Coan both recommend synthetic fluid for race applications.

Rich Krause

 

More thoughts for you:

1) Is transmission builder who warrants it comfortable with 250F ?

2) Smell the fluid. Does it smell burned?

3) Check the accuarcy of the new gage. Boiling water is a good way to test it. If it's a gage reading 20-30 degrees high, there's not much problem.

4) Is there a restriction in the cooler in/out lines slowing down the flow? Kinked line perhaps? If you have an IR thermometer, point it at the cooler right after shutdown to see if it's hot.
Also check the pan surface with the IR gage right after the run.

My $.02

 

Based on my experience with a TH400, manual valve body, 20+% slip non-locking convertor, launching at 5K on a 300-shot, 250-deg without the juice sounds too high.

My trans builder recommends ONLY synthetic. I have a Perma-Cool fan assisted cooler. If I see the temp getting anywhere near 250degF, I know I forgot to turn the fan switch back on.

 

I have that neat B&M with the thermostatically controlled fan, turns on at 160 degrees.

Rich Krause

 

Thermostatic switch...... good idea. I only put a manual switch on mine to eliminate the load on the battery for the 5 minutes or so it takes to download the data from the MoTeC after a pass... it was getting annoying having the tranny cooler fan running the whole time..... but I have forgot to turn it back on more than once, only realizing it at the end of the next pass, when the tranny fluid temp was starting to run high. Old age is a bitch

 

Here's a question for you Fred...What exactly "makes" a fluid "synthetic"?....
Not just what properties that it possesses, but the basics of what makes a fluid synthetic..........
(lose your keys lately?)...

 

I know you asked Fred, but from Amsils website:

In 1999, the National Advertising Division of the Council of Better Business Bureaus ruled in Mobil Oil’s challenge that Castrol’s “advertisements inaccurately represented that the current formulation of Syntec is synthetic”. Mobil’s position was “true synthetics had to be formulated from small molecules subject to a chemical reaction, not built from natural petroleum”. Castrol uses a “hydroprocessed mineral oil” (a Group III base stock) as the base stock in their Castrol Syntec. Previously, synthetic oil was accepted to mean the base stock was not conventional petroleum oil, regardless of refining process. This ruling changed all that.

The most popular and best performing conventional base stock was formulated with polyalphaolefin (PAO), together with other non-petroleum products, such as ester, to achieve optimum performance and seal swell. This is in essence the base stock used by AMSOIL.

People are more than a little surprised when they hear that many oils now on the market that are labeled as “synthetic” are really conventional oils. They are being advertised and labeled as synthetic oil, but are really specially refined conventional petroleum oil. People ask me how these companies can do that.

I first included in this newsletter over a year ago excerpts from an article in Lubricants World Magazine entitled “A Defining Moment for Synthetics” which reviewed the facts and circumstances around the challenge made by Mobile against Castrol’s advertising. In essence, the term “synthetic” was determined to not be a scientific term, but was judged to be a marketing term. The definition of synthetic lubricants was broadened to the use of the term “synthetic” in referring to motor oil that had the ability to provide synthetic performance, but without defining synthetic performance. In other words, beauty is now in the eye of the beholder – but without full disclosure!

Now, as a result of this ruling, many of the labels on motor oils that you see on store shelves that say “synthetic” is not a synthetic (in the classical sense), and could now be what used to be labeled a “synthetic-blend”. According to Lubes n’ Greases magazine (July 2001), “…most large lubricant producers moved quickly to replace PAO with Group III base stocks in their synthetic [passenger car motor oil] formulations.”

How can you tell? Price is one way. Hydrocracked oil, according to Lubes n’ Greases magazine, is $1.50 to $2.00 per gallon cheaper, half that of PAO’s.

But if it is labeled as a duck, does it walk like a duck?

According to Lubes n’ Greases magazine, “PAO has a significant advantage in low-temperature performance. This could prove to be the handhold needed to pull base stock demand out of the [Group III] space and into PAO territory. Market development will be slow, but auto makers specifying the use of 0W-30 and 0W-20 engine oil would drive such a victory. Since PAO may be the only show in town to met the cold-cranking specification for these grades, ultimately this could result in a prize for PAO bigger than the one it lost in its first major battle with Group III.”

Rich Krause

 

Very interesting read...
So, if I purchase an "off brand" full synthetic, I may not really get what I bargained for...
I would think that there would be tighter regulation on specific oils, but I guess $$$'s govern the oil market legalities...
Interesting never the less.......

 

Think of "synthetic" as "a designer molecule."

Conventional ("mineral oils") are a mix of various cuts of crude oil components that have been seperated from the crude in various distallation processes. A book I have describes these as a "stew of various hydrocarbon molecules.... consist(ing) of dozens of varied hydrocarbons". "Synthetics are "chemically" disassembled/reassembled molecules that are synthesized from homogeneous light-weight "crude" molecules into higher weight molecules tailored to a specific lubrication purpose. Synthetic oil production begins by producing ethylene from crude oil or natural gas. Ethylene is turned into alphaolefins (low-weight synthetic hydrocarbons) that are then polymerized into polyalphaolefins (PAO) of heavier molecular weight. Syhtnetics also contain esters (acid/alcohol compounds). They must be carefully blended into PAO's which are thermally stable over a wide range, but not particularly compatible with additives." In other words, they add the esters so that additives can be put in with the "designer" PAO molecules. Additives such as detergents.

Addvantage of synthetics:
-ZERO wax (can not be totally eliminated from distilled blends)
-lower pour point, better flow at very low temps
-high resistance to thermal breakdown
-maintain a uniform viscosity over a wider range of temps
-resist long term breakdown and thickening under high thermal loads.

One way to think of "conventional" lubricants, in simplified terms, is to think of taking a big barrel of crude oil, and seperating it into its various components using distillation. You end up with a lot of the molecules you want, but the distillation process inherently ends up with small parts of the components you don't want. Then they attempt to alter the molecular structure by adding "viscosity extenders", so that the oil will flow easilly at low temperatures, and stay reasonably thick at high temperatures. But these "viscosity extenders" are long chain, coiled molecules that expand and contract with temperature to alter viscosity (thickness). They are "mechanically" altering the viscosity, and when these long-chain molecules break down, either chemically due to high temperatures, or mechanically due to shearing forces, the "multi-viscosity" of the conventional oil disappears.

Synthetic molecules, on the other hand, are produced chemically to be essentially one type of molecule, with the viscosity properties that the typical lubricant requires.... flows easilly at cold temps so you get good oiling at startup, and keeps the required viscosity under a wide range of operating temperatures so that uniform lubrication is always present. And, these "designer" molecules are stable at much higher temperatures, and are not easilly detstroyed by the shearing forces involved n lubrication.

Good reading:

"High-Performance Automotive Fuels & Fluids", Jeff Hartman

 

Fred,
Does Hartman's book cover anything on race fuels and the 'synthesized' components used in them? From our other topic on VP fuels.... just raises some interest for me.

-Mindgame