Trust bearing !!!
- Thread starter GN280CI
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There will be much less of that effect with the restricting orifice in place. Particularly if the size I recommend is used.
The larger the orifice, the more chance main line pressure changes will have an effect on converter charge and cooler line pressures.
Using my car as an example, I installed a tee block in my cooler line so that I can very easily check my cooler line pressure at any time I please. I've played around with my main line pressure and found that my cooler line pressure continues to hover around 40 psi even with changes to main line. I remain a happy camper.
What size is the orifice you're using?
Let me tell you one of the reasons I picked 7/64" for the orifice.
Being a transmission technician since the early 1980s, I've seen many valve body kits, or commonly called shift kits. Although, the phrase 'shift kit' is actually trade marked and shouldn't be used when talking about valve body recalibration kits from competing manufacturers.
I've seen a lot of valve body kit instructions for high performance use. I quickly realized that there was one particular size used when a max firm shift was desired. That size was 1/8". Then there was this one instance at a transmission technical seminar when a technical speaker was talking about orifices for something or other and mentioned that if you wanted to remove a restricting orifice, just drill it to 1/8". In the transmission world a 1/8" hole is considered an open flowing hole. It offers no restriction to flow as far as valve body flow goes anyway.
7/64" is 1/64" under 1/8".
In some valve bodies, inorder to keep some valves from buzzing, a balance passage restriction must be used to slow flow down and control pressure pulsations. Some of those passages have to be under .050" in diameter to slow the flow enough to control pulsations.
Also consider this. A 7/64" orifice will control cooler line pressure to 40 psi, but the hole is still large enough to easily allow one quart of flow in 20 seconds, considered the minimum flow requirement for proper trans cooler and trans lube circuit function. As I mentioned earlier, I have experimented in the past with smaller sized orifices and still maintained a flow of one quart in 20 seconds.
Being a transmission technician since the early 1980s, I've seen many valve body kits, or commonly called shift kits. Although, the phrase 'shift kit' is actually trade marked and shouldn't be used when talking about valve body recalibration kits from competing manufacturers.
I've seen a lot of valve body kit instructions for high performance use. I quickly realized that there was one particular size used when a max firm shift was desired. That size was 1/8". Then there was this one instance at a transmission technical seminar when a technical speaker was talking about orifices for something or other and mentioned that if you wanted to remove a restricting orifice, just drill it to 1/8". In the transmission world a 1/8" hole is considered an open flowing hole. It offers no restriction to flow as far as valve body flow goes anyway.
7/64" is 1/64" under 1/8".
In some valve bodies, inorder to keep some valves from buzzing, a balance passage restriction must be used to slow flow down and control pressure pulsations. Some of those passages have to be under .050" in diameter to slow the flow enough to control pulsations.
Also consider this. A 7/64" orifice will control cooler line pressure to 40 psi, but the hole is still large enough to easily allow one quart of flow in 20 seconds, considered the minimum flow requirement for proper trans cooler and trans lube circuit function. As I mentioned earlier, I have experimented in the past with smaller sized orifices and still maintained a flow of one quart in 20 seconds.
Do not confuse the suggestion of a torque converter feed restriction for a restriction in the transmission cooler lines or transmission cooler system overall. The transmission cooler system should be as free flowing as possible. Minimum 5/16" ID throughout the system.
Another interesting fact. If you study the T/C feed orifices of transmissions designed after the 1960s, you will notice many of the feed holes being even smaller than the 7/64" that I recommend. Hmmm. Think maybe some transmission engineers learned something?
I've used both 7/64 and 3/32. What I've found is the return or exhaust out the converter has a role in the feed presure as well.
That's correct! That's why I stated that the cooler system must be as free flowing as possible.
It's sort of like lubricating the center section of a turbo. The oil drain pipe after the turbo must be large enough so that oil doesn't back up and start building pressure in the center section. Of course, some pressure does build up in the torque converter, but you get the idea.
Lazaris. If cooler pressure is varying significantly with line pressure changes after adding the orifice, you should check for crossleaking or just replace the pump assembly.
One way that oil pressure can bypass the pressure regulator assembly all together and affect T/C charge pressure is running too much pump gearset face clearance. .001" to .003" is the acceptable range. I always shoot for .001" to .0015".
Something else to check. After doing the mod, always run a mill file across the surface of the pump cover to knock down any raised metal that always occurs because of the drilling and tapping of the feed hole. This raised metal, if left alone, will prevent the two halves of the pump coming together completely to seal hydraulic passages in that area of the feed hole. Cross leaking will happen because of this.
This next tip has nothing to do with T/C over charging.
Another source of a cross leak that is widely ignored is the rear bushing in the pump cover. This bushing has the job of supporting the rear of the input shaft and also separating torque converter feed oil going to the torque converter (post orifice) and lube oil returning from the cooler. If this bushing has anything more that .001 to .002" clearance, T/C feed oil will bypass to the lube circuit of the transmission, and flow through the T/C and cooler will be affected. The common symptom observed from this is higher than usual trans temps since oil flow through the cooler is slowed down by this cross leak.
One way that oil pressure can bypass the pressure regulator assembly all together and affect T/C charge pressure is running too much pump gearset face clearance. .001" to .003" is the acceptable range. I always shoot for .001" to .0015".
Something else to check. After doing the mod, always run a mill file across the surface of the pump cover to knock down any raised metal that always occurs because of the drilling and tapping of the feed hole. This raised metal, if left alone, will prevent the two halves of the pump coming together completely to seal hydraulic passages in that area of the feed hole. Cross leaking will happen because of this.
This next tip has nothing to do with T/C over charging.
Another source of a cross leak that is widely ignored is the rear bushing in the pump cover. This bushing has the job of supporting the rear of the input shaft and also separating torque converter feed oil going to the torque converter (post orifice) and lube oil returning from the cooler. If this bushing has anything more that .001 to .002" clearance, T/C feed oil will bypass to the lube circuit of the transmission, and flow through the T/C and cooler will be affected. The common symptom observed from this is higher than usual trans temps since oil flow through the cooler is slowed down by this cross leak.
Correction to my last post
The flow through the T/C will not be affected by this cross leak since the cross leak is occurring after the T/C. Ooops again.
The part in bold should be, exiting the torque converter and going to the cooler. Ooops.
The flow through the T/C will not be affected by this cross leak since the cross leak is occurring after the T/C. Ooops again.
A story about having too much pump gearset face clearance.
In the 1980s we were dealing with 3 speed Chrysler Torqueflites (727, 904) that used lockup torque converters. You didn't dare build one with over .002" face clearance. If .003" was used, the output pressure from the pump gearset would cross leak directing into the torque converter and cause the engine to die when shifted into reverse. This was caused by the cross leak causing the lockup clutch inside the T/C to apply.
In the 1980s we were dealing with 3 speed Chrysler Torqueflites (727, 904) that used lockup torque converters. You didn't dare build one with over .002" face clearance. If .003" was used, the output pressure from the pump gearset would cross leak directing into the torque converter and cause the engine to die when shifted into reverse. This was caused by the cross leak causing the lockup clutch inside the T/C to apply.
Don I'm running the pump I bought from you. So I know you did all that stuff already. I was just making a point that the feed pressure is only one area to look at. The fluid being able to return or exhaust will effect the feed pressure no matter how small you make the orifice. I actually removed my pump bushing because the converter I use has one. This reduces the back pressure (return). I also incorporate another device in case of a spike in pressure.
Have you ever seen some of the real fast cars leave during dusk or night off of the trans brake? You will actually see sparks come out from the middle of the car. Do you know what that is? It actually pretty amazing. I have see it alot on some really high HP cars that need the line presure to make the tranny live. I have a video of Dan Millen's car doing it. Its occuring right after trans brake release when the feed pressure spikes.........
What does your cooler system look like? You've got my curiosity up. What kind of variance in cooler pressure do you see?
The sparks. Starter gear being thrown into the ring gear?
Typically this is the weak bendix in the starter. On launch, the spring will be overcome for a second, and the gear on the starter hits the flywheel causing the sparks.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
OR -the converter is getting pushed out of the trans. , bending the flex plate
which in turn ends up hitting the starter pinion. This the the same action that takes out your thrust bearing!!! Mike
I see these sparks pretty regularly at the local heads up races during the night runs.
I saw what the effects were a few passes later. The converter had pushed hard enough on the flexplate to bend it. It pushed so much so that the heads of the bolts holding the converter to the flexplate had gotten into the oil galley plugs of a small block. It easily cut .100 off the height of some of the plugs. This means the converter had to try and move off the pump at least 1/8 of an inch.
Same situation with a Buick V6. The converter pushed far enough forward to make the flexplate chew into the starter.
Thats is exactly correct. Hence this the force that eats the thrust bearing.
Don I use a Setrab cooler. I saw variences in pressure non proportional to the main line pressure changes. IE: 40 psi increase in main line did not raise cooler out pressure 40 psi. It did however raise it say 20 psi.
What you see at idle or in gear for cooler out pressure or even with a raised rpm in park or in gear does not remain constant. The pressure will spike after transbrake release and some times near the finish line as well.
