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Stall Speed and Transmission Servicing Q's

 
Old 11-25-2007, 12:16 AM
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Dwayne
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Question Stall Speed and Transmission Servicing Q's

Now that I'm finished with the engine and front end, I'm working my way back to go through the rest of the major mechanicals. I'd like to go through the transmission and rear end next. The transmission is leaking so I'd like to replace all the gaskets, seals and hoses. Operationally, the transmission performs fine except I think the stall speed may be on the low side. I performed the tests in the manual, vacuum is at spec, bowden (sp?) cable has been adjusted to take out the slack. I performed the stall speed test according to the manual but I didn't have an external tach so used the instrumentation tach. I got 2100rpm for the stall speed. The manual says it should be 2400 +/- 200. I take that to mean 2200-2600 is acceptable. Since my altitude is about 2400 feet, I should loose approximately 100 rpm on the stall speed - I'm assuming if I ran the test at sea level, I'd get about 2200 on the stall speed which is right at the lower end of the "acceptable" region.

So here's my 1st question, I've been reading on this forum about raising the stall speed by making modifications to the TC. Can I raise my stall speed by say 400rpm (to about 2500) by modifying the TC?? If so, what will be the effects on driveability since the new stall speed would still be within factory recommendations?? Will it have a quicker take off from a stop?? Will it impact other areas that would be undesireable?? Is there something else that may be causing the lower stall speed other than the TC that I should test/look at??

My 2nd question, While I have the transmission out, are there some "while I'm in there" things I should inspect/repair/replace in the transmission?? How much of the transmission should I take apart and inspect??

THANKS (from a newbie) for any advice/recommendations!
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Old 11-25-2007, 12:47 AM
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killav
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Search for posts by me pertaining to torque converter stall speed back in 2006. I increased my stall speed to about 2400 from a very low factory 1800. I used a place called Texas Torque converter. I posted the phone number in the old thread. It only cost me about 170 bucks to get the converter completely rebuilt and the stall speed increased. He has all of the equipment to do this. All he had to do was machine .250 of an inch off of the blades on the turbine. I think it was the turbine. Your stall is already much higher than mine was (mine is an 87). So .250" might be too much for your 84. You might want to talk to the guy first before deciding. Maybe take off .125 to .1875 of an inch if you decide to go that route. He commented on how robust the guts were for a stock converter. If I were you, I wouldn't burn the cash on just a rebuild unless your serious about wanting more stall speed.

The change in drivability was greatly improved for my car. But like I said, my stall was really low. I suspected that my one way sprag clutch was bad which will cause a lower than normal launch RPM from the converter, but he said it was fine. Drives great even on the highway. I thought I would notice some slipping at freeway speed below 2400 rpm but this is not the case.

Also, the shop that did the work for me said that .250 of an inch cut off the turbine would net you about 400 more rpm from the stall converter but mine ended up getting 600 rpm's. This worked out perfect for me since mine was an already low 1800.

And finally, replace the front seal in the transmission while you have the converter out.

Trans filter and Gasket also.

Last edited by killav; 11-25-2007 at 01:02 AM.
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Old 11-25-2007, 01:40 AM
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perrys4
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There should be some good threads on the stall speed and the TC by Pappy. He had a killer 928 setup and had a full test and disclosure written up about it. He even has the name of the people that did the build for him. I will look for it but you can likely find it just as easy.
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Old 11-25-2007, 01:51 AM
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Looks like Steve was running stall speed at 2700 and I think these guys did it for him. For search purposes his name is Pappy92651

http://www.edgeracingconverters.com/products.htm
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Old 11-25-2007, 01:57 AM
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I have done the change to the TC. If you want to keep the car "comfortable, do not exceed 2400rpm. You will end up with a herky-jerky/sensitive ride....unless of course you like that kind of thing. Just imagine being in 1st gear on a manual and blipping the throttle around town....it gets old quick. I used Edge as I lived a couple miles from them. I spoke to the owner and I got what he recommended for my car and still kept it drivable. If you really want to dial in the stall speed, you need to get your car dyno'ed and figure out what you crank hp and torque are and at what rpms...this is the ONLY way to get what you need and want.

You really shouldn't have to do anything to the tranny, beyond pulling it and replacing the TC seal and I STRONGLY recommend replacing the pump gasket. You should have to do nothing else. All of your adjustments are external. Make sure your cables are tight on the re-install and and set you shifting to near redline...at least that works on the 3spds, not sure about the 4's. You will have to drive, adjust, drive, adjust, but the end result will make a world of a difference. Porsche made these and adjusted to please the norm. You can tweak them some and it makes a nice difference.
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Old 11-25-2007, 11:12 PM
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Thanks for the tips and advice. I think I'll hold off on the TC mod and consider getting the car dyno'ed as Keith suggests. I think it's best to find out exactly what I've got and exactly what I'd need to get the TC to 2400 stall speed. So I'll sit on this one for a while and maybe talk to the guys at Edge and Texas Torque Converter for additional research.
For now, I'll plan on the following transmission repairs: TC seal, pump gasket, trans filter, pan gasket, hoses. THANKS again for the help!
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