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Discussion Starter #1
I am on my third set of pump gears in my Th-350 trans. It's the only thing i am breaking in the transmission. When i take it apart the rest of the transmission looks nice. I just broke the last set this weekend. It's only a 500 hp engine in the car and no trans brake, 9" tire.....

The first 2 sets were stock gm units. The last set i got from my transmission wherehouse. They looked like china junk to me but i thought i would try them any way....

Any ideas of what to look for as a cause???? i did not get the trans out yet. It may be a week or 2 untill i do.... Are there any aftermarket high performance pump gear sets?????

thanks,Keith
 

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There is only a couple of aftermarket pump gear manufacturers and the gears they supply are just not as nice as the factory gears were, but they seem to work just fine.
If your smashing gears or breaking off the drive tangs there is a few things to check.
Make sure your engine block dowels are extending far enough into the trans case to pilot the trans case, and not just sitting on the chamfers of the dowels and the case.
Check the pilot of the converter where it engages the crankshaft, make sure that it does engage and that the crank pilot hole and the converter pilot are of a similar diameter ( within .003" of one another, smaller on the converter) and that there is engagement in the crankshaft. I have seen press on pilot rings forgotten or that have fallen off.
The clearance when the trans is bolted to the case between the flexplate to converter pad area is to be .125" to .187" .
Check the converter pump drive next time you install the converter and make sure that when the converter is in the trans and bottomed out, that it is bottomed out on the pump drive tangs. Put some lube on the converter and check for a wear pattern that indicates the hub is against the front edge of the pump tangs and not bottoming out on the input shaft of the trans first.
If this happens, the converter neck will be barely engaged in the pump gear and will kill the pump eventually. The same will happen if the converter is too far into the trans. Clearance is critical.
When you take the trans apart is there any indication that the inner pump gear has ground into the rear half of the pump? Let me know.
Also . after a pump has grenaded, I don't recommend installing gears into the damaged pump pocket, usually the pump castings are distorted. The neck of converters that have had this type of truma are equally suspect of problems. I suggest after doing the above checks that a new converter neck be installed before trying this again.

Hope this helps, Hutch
 

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Discussion Starter #3
trans

Thanks Hutch, It really helps.

I do know the trans is correct on the engine pins, and i know the clearnace between the converter and the flex plate is about .150"

I will check all the rest of your suggestions.I printed them out for reference.

What it is doing is splitting the outter gear down in the root of the gear. Well that is what happened the first 2 times. It happens over a period of maybe a year and a half. That would be maybe 1000 street miles and 25/30 1/4 mile shots......

The first ime i did put a entire different pump in it. This last time i believe i re-used the housing. I'll need to look at my notes....

The outside of the outter gear and the housing has always look good with not scoring on them....

thanks again, Keith
 

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One more note. Inspect the trans case where it meets the pump face and pump gasket. Sometimes the case has so much cast flashing in there it rectricts the pump suction side 50% or more. Clean it out to the full case dimension. If the pump starves for oil it can lockup the outer gear, also make certain the filter you are using is a screen style, I prefer them over the dacron (felt) style.

Take care ,Hutch
 

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If you just replacing the gears in a turbo 350, you have to be careful because they make 3 or 4 different thickness of gears. If the gears are wider then the pump is designed for, the gears will be frozen/vised between the two pump halfs. Measure the depth of the pump where the gears set as compared to the replacement pump gears thickness. Should have about .03 clearance, if the gears are the same as the pump cavity in the pump or thicker, the converter will have a hard time rotating the gears thus braking them. When the pump is repaired or put together, try the converter in it and rotate it before installing the transmission. Hope tis will help you in someway. Burt www.burtbrownracingtrans.com
 

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Hopefully after 5 years from the original post K-star got the problem fixed
 
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