HEAT might not be the prime cause of tranny failure

[Joe 90]

If heat really is the No.1 cause of tranny failure, I would be curious to know if ANYONE EVER had the "AT TEMP" light come on while driving..?

I just got my car back from the shop where I had my transmission rebuilt after failing last week and talking with the technician (and owner of the shop) who is also a good friend and no BSer, he told me that my tranny did not overheat. He says that the OEM cooler is plenty enough for this climate (eastern Canada at least) and that it would not be necessary to had a second one. Besides, he asked did the "AT TEMP" ever came on while driving the car..??? My answer was NO… Never saw this light ON….

Which makes me wonder if HEAT really is the source of all those tranny failures? In fact, this technician who worked on mine says that Wear caused by the incapacity of the tranny to limit the slippage between the clutch discs under hard accelerations (due to the high level of torque of the engine) causes the wear. Which means that in time, this small but constant slippage between the clutch discs leads to premature failure.

This is the result for having the manufacturer creating a luxury sports coupe that have shift points that are smooth as silk.

The solution to this, is to limit the slippage when shifting by increasing the hydraulic pressure holding the clutches together. This is done by replacing some of the springs regulating the pressure. In fact, any other "so-called" heavy duty mod on these transmissions is illusive. True that if you limit the "slippage" and you make the tranny shift harder it should last longer BUT this does not make the it any stronger.

[svxxx26]

About the AT TEMP warning light, from what I have read over the past year or so is that the tranny temp has to be ultra-high to even kick it on - meaning in the event it did come on, it would be more or less telling you to start checking your wallet! A high, potentially damaging temp wouldn't activate the light. The result of this is a worthless warning light - even dangerous. It gives false confidence to the uninitiated.
This is why my summer SVX project is to install a tranny cooler AND ATF temp gauge.

[Phast SVX]

Just got my guage and cooler installed by greg(Svxboy) last week. We had a warm afternoon, it was in the 70's and wiht a little bit of speeding around and stop and go driving i have yet to go over 160,on normal driving, it does not even go ober 140. The car runs very cool on highwya driving, but not to cold to shift into overdrive. YOU NEED TO GET THIS DONE. Check the factory Filter when you do so, mine was on backards!

[svxxx26]

<<This is the result for having the manufacturer creating a luxury sports coupe that have shift points that are smooth as silk. >>

First, a disclaimer: I am not a tranny tech! But, I would be skeptical about that being the cause.
I'm sure that the SVX was/is not the only luxury sports coupe out there. Do they experience the same sort of problems? For that matter, does any luxury car?
While it might not help - I wouldn't think that the shift points could be blamed for our tranny failures.
Anybody have a more informed opinion?

<<Anybody have a more informed opinion?>>

The best I can tell, from talking to a friend who builds racing transmissions, is this: A clutch that engages smoothly is doing so by slipping. Slipping causes friction. Friction causes heat. Heat needs to be dissipated. Back to slipping. Slipping causes wear. Wear causes fluid contamination. Fluid contamination causes filter/cooler clogging. Filter/cooler clogging causes high heat. High heat causes slipping.

A smoothly shifting trans causes more heat which causes more wear which causes more heat which causes more wear which caused more heat which causes more.......

The quicker the clutch engages the less heat and wear are experienced. BUT the more stress is put on the rest of the drive train. My 98 Forester shifts very crisply compared to the SVX. It also is only being powered by a 2.5 L at 165 HP.

My tranny building friend has an automatic in his drag car. When the light turns green there is 18" of daylight under his front tires. But there is a LOT of metal holding things together on the machine. Somewhere in between lies the answer.

John

[svxxx26]

Ok, here's a question:
Assume you have a brand-new SVX. Is it prone to heat-related tranny problems as is, or does it need to have the factory tranny "cooler" clogged up first?
If so, then an aftermarket tranny cooler hooked up in parallel or bypassing the stock cooler altogether should solve the problem - or a pricier solution might be to replace the radiator with the updated, supposedly clog-free cooler.

<<Ok, here's a question:
Assume you have a brand-new SVX. Is it prone to heat-related tranny problems as is, or does it need to have the factory tranny "cooler" clogged up first? >>

Smooth shifting will cause the clutches to wear and also generate heat. There is always going to be some heat and slipping. Reading historical postings what I have gleaned is that the early model coolers have a mesh inside them that is prone to clogging because it acts as a sort of filter. I recall it is also not easily flushed or flushed successfully. Later models apparently did not have this mesh and related problems. The addition of a filter was supposed to cure the cooler clogging problem. But a filter will also clog if not replaced (like mine did) and will cause trans problems. I'm sure there are mods that can be done to change the way the thing shifts and, possibly, extend its life. A cooler in parallel with an inline filter would also help. Although the cooler with the least resistance will get the majority of flow and this may not be the cooler offering the greatest cooling capacity. For instance, if you install a straight pipe and the worlds best trans cooler in parallel the fluid will likely flow through the pipe and bypass the cooler altogether.

I opted to bypass my questionable stock cooler (likely clogged) and installed an aftermarket cooler and stock filter. Time will tell I guess.

[svxistentialist]

We have very few automatics here in Ireland [second hand market resists them like the Black Plague], and what I know about them would fit on the back of a stamp.

Why I have bought one with a world class failure rate is one of the Sorrowful Mysteries.

Agree with lightning's racing buddy about the vicious circle of friction heat and insufficient cooling. Mine's a '92, and if I can get a '94 stock rad from a scrap yard without the mesh in the circuit, I will go for it. All later cars were retrofitted with a factory in-line filter to stop the sludge clogging up the cooling circuit.

My idea of the optimum set-up for an SVX would be this;

1. A stronger flow rate for the ATF to ensure fast liquid to liquid cooling under high heat conditions, towing or drag racing or such. I believe Level 10 does a pump upgrade to achieve this.

2. An additional cooler plumbed in parallel to the stock circuit. This should have sufficient size to cool as effectively or better than the stock one.

3. Put the extra cooler in a position where the radiator fans pull air across it when the car is in slow traffic/hot day scenario.

4. Put a temperature controlled solenoid valve into this extra cooler circuit so that oil does not flow to the new cooler until it has reached normal or near normal temperature. Otherwise, the combined effect of both coolers will keep the box too cold for TC lockup, and affect fuel consumption and driveability. This valve would be NECESSARY in a cold climate, I think. Rally cars use this trick to keep the engine oil warm enough to reduce friction[release horsepower] but add additional cooling when the going gets hot.

5. Connect a temperature gauge into the circuit to keep an eye on what temperatures the box is getting to under different climate/driving style/traffic conditions.

6. Use Redline High Temp ATF fully synthetic oil.

Do all this, the tranny should last. Final point: I think [very] high temperatures are the biggest enemy of long life, rather than the smooth slurred high friction shift. The friction material in the clutches breaks down under ultra high temperatures, which accelerates the demise.

Joe

[Aredubjay]

<<Why I have bought one with a world class failure rate is one of the Sorrowful Mysteries. >>

Joe, it's no mystery to your fellow owners -- no mystery at all.

<<Why I have bought one with a world class failure rate is one of the Sorrowful Mysteries. >>

This one is easy to answer. Go in the garage and look at the damn thing! Then drive it. Nuff said.
-joe-

[svxter]

Speaking of transmissions - if you haven't already done so, please go punch the proper button in one of the transmission failure rate polls. Thanks to the 35 or who have entered their information. Surely need to get more data, though.

[svxistentialist]

Thanks Bill

I've polled. Results are interesting, but skewed. '92/3 cars show the most problems and repeat tranny fixes. You would expect this if only for the higher mileage.

Newer cars don't show the same level of problems. Again, lower mileage is a factor, but I am wondering about the owner profile, maybe the older cars are bought cheaper by inexperienced and younger buyers, who are not too simpatico in engineering terms.

Not enough data to draw firm conclusions really, I am merely surmising out loud. One thing does occur, though. If the tranny is being refurbished in an early car, then a new or later rad should also be fitted, one without the mesh.
This mesh, if clogged , is going to make a good flush impossible. It may also impede oil flow, an instant kill factor if a series auxiliary cooler is installed. This is what I am suspecting is causing all the repeat failures in these models.
Can you do a poll to see how many repeat failures there have been with an extra cooler installed, whether series or parallel, and was fully synthetic ATF in use?This would be an interesting statistic.
Joe

[svxter]

You're absolutely right about all the points you make. Mileage, frequency of maintenance, type of driving, and a host of other factors come into play here, and would have to be taken into account in order to draw any valid conclusions. The addition of auxillary coolers and use of synthetic ATF should also be considered.

Since the polling tool is a rather blunt instrument for doing this sort of work, I had thought to do a series of them. Once there is some overall qualitative feel for things, I had thought to do some more focused sorts of things. The question you suggest is certainly a good one, and could easily be done.

I don't think this software would support a form - if it did, that would really be the way to do it. A nice survey instrument could be designed, but I don't think that's possible here. Maybe an e-mail survey at some point? Anyway, just thought this could be a first cut at it.

[svxistentialist]

Yeah Bill,

Good approach. On-line forms are useful, but impatient ol' me keeps coming unstuck with them.

They are designed by navel gazing anoraks, who put in required fields like "Post Code", when you are e-mailing from Patagonia.
Then they don't put in a Thank You for Posting note, so you submit twice or three times for luck.
Rant mode: off.

An e-mail designed like a form that respondents could quickly fill in the slots and reply would do the same thing. They would all need posted to the same address though, so that they could be checked as unique.

Count me in if you are doing it.

Joe

[svxter]

I probably will at some point. It's just the statistician in me that keeps coming out.