Torque Converter Questions

[GsxrMike]

Ok, I'm getting ready to overhaul my TH400 and wondering if I should replace my torque converter. I'm running a mild 350/400/208/4.56, trail only rig, I can't remember the last time I had it out of 4 LO and its fairly rare that I get to third gear. I don't know much about stall speeds but I run an aftermarket transmission cooler (the biggest one they had on the shelf at the auto parts store 5 years ago, probably 20"x12"x1") so I don't think heat will be an issue (I also have dual electric fans so I can keep air flowing across the cooler independent of engine speed. I've also got a transmission temperature gauge so I can keep an eye on temps. Most of what I do is slow rock crawling type stuff with the occasional muddy field or mud hole. My truck is probably close to stock weight, if not maybe a little under. I'm thinking with a higher stall converter my engine will spin faster while I'm trying to crawl up a trail keeping me higher in my power band and the only trade off would be heating the transmission fluid. Is this accurate? What kinda stall speed should I look into if I go higher? (BTW I searched but didn't find really what I was looking for) Also, what's the maximum transmission fluid temperature I should run before it starts breaking down? Also, any recommendations on tranny fluid when I fill it back up? Thanks guys!

 

[Cili]

I don't have a recommendation on a converter but I do recommend using dex vi fluid. It is a lot more expensive but it is worth the expense. I believe GM says dex vi is rated up to 265 degrees before it starts to break down, although I would never let my Trans temp get that high.

 

[blazinzuk]

Stock on the stall.

 

[GsxrMike]

Any particular reason blazinzuk? And should I just keep the stock one I have or install a new stock converter?

 

[blazinzuk]

Any particular reason blazinzuk? And should I just keep the stock one I have or install a new stock converter?

Higher stalls creates heat. In trail rig that is geared well you don't need anything other than stock. Gearing let's you crawl not power. A higher stall can let an engine be more in its power band. In a trail rig if you are constantly launching up stuff I can see it being worth while. But in crawling with a higher stall its just going to create heat because you are on the converter more than with a lower stall

 

[CGT80]

If you had metal floating around in your trans, replace the TC. My uncle owns a trans/auto shop and is a mechanic. The only way to clean out the TC is to have it rebuilt or get a new/rebuilt unit. The old TC will send that old metal into the inside of the trans after it is rebuilt.

If your trans is still good, but you are just rebuilding it for the hell of it, them maybe you could reuse it.

 

[blazinzuk]

Oh one other thing. New transmission=new convertor, not worth the risk

 

[Greg Ducato]

Higher stalls creates heat. In trail rig that is geared well you don't need anything other than stock. Gearing let's you crawl not power. A higher stall can let an engine be more in its power band. In a trail rig if you are constantly launching up stuff I can see it being worth while. But in crawling with a higher stall its just going to create heat because you are on the converter more than with a lower stall

Good advice here. The 400 converter is 13 inches in diameter and holds a great deal of fluid, it is a good crawling choice. If you need more stall to keep from pushing through the brakes in some situations, I would suggest the high stall 400 converter as used in some V-6 applications in the late 80's. That will give you slightly more stall but still stay reasonably cool. If you arent doing so already and have the ability to, run the trans cooler line to the radiator cooler first, then back to the aux cooler, then back to the trans.

 

[6.2Blazer]

For what a new converter cost compared to rebuilding the tranny I would highly recommend getting a new one. Dex VI fluid also as it is supposed to hold up better than previous versions.

 

[GsxrMike]

Thanks for all of the advise guys, nothing wrong with my transmission now except that it leaks fluid like crazy. I got one of the fancy overhaul kits for like $200 bucks and an SA Design book on how to rebuild. If the transmission looks good inside then I'll run the TC that I have, if not I will replace. I'll look into the Dex VI fluid. Once again, you guys are the chit! Thanks a million!