Supercharged 5.3 (GMT-900) - will stock(ish) torque converters live?
 

I finally pulled the trigger on a Magnusson supercharger for my '07 Silverado 1500 4x4 with the LMG. Also will be doing a Truck Norris cam, AFM delete with new lifters, with American Racing long tube catted headers (finished off with a full dyno tune, of course). I've already got a PerformaBuilt Heavy Hauler 4L60E with 5-pinion planets, beast sunshell, and Sonnax Smart Tech drum, along with all the associated mods in the Heavy Hauler line. I was told by the builder that the torque converter is the weak link in all this. It's an FTI converter (unknown p/n or model) - all I know is it's painted black and has a 2k RPM stall since I tow frequently.

All that said, I've seen posts on here of guys running boost through the stock torque converter, and I assume this FTI converter was built based on the stock unit (probably uses the stock lockup clutch inside). As you can probably tell, I'm dreading having to touch this transmission again - the install was a friggin NIGHTMARE straight from hell. If I can get away with leaving this converter in here, that would be fantastic ... but if there's any doubts as to it's longevity, I'll have to pull it. I've got $5k into this trans and can't afford to break it pumping metal through it.

What say you guys? Should I just put a converter in that's built for boost, or can I run this stockish FTI? The converter works FANTASTIC, so I'd hate to lose that. Made the stock truck feel like it gained 100 ft. lbs. off the line - dramatic difference. I bought the truck brand new, and it was always weak off the line. Not anymore. It will actually squeal the tires now if I stuff it.

Anyway ... anyone run boost through a stock converter, beating on it and towing for many tens of thousands of miles?

EDIT: Just as I posted this I received an email back from FTI on this converter. Unfortunately I'll be exceeding the limits of this converter. What do you guys recommend for a low-stall towing converter that can handle boost?

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I'd fill out the "Ask CDS" form on the Circle-D web page with all your trucks specs then either Brian or Chris will reply via e-mail. For a bulletproof street setup in your stall range I'd go with the 265mm triple disk. With the triple you can lockup the converter WOT with no clutch wear issues. They have a 4-5 week build time so get the ball rolling ASAP. The FTI converter will be ok while you wait but try to avoid WOT lockup on the stock type lockup clutch.

Be sure to change out the filter during the Performabuilt specified mileage. If you can achieve break-in on the FTI you'll save money on fluid & filter when you install the new converter if your in that window. Performabuilt tags the bottom of the filter during the build so they'll know if the filter has been serviced if warranty issues arise. Frank is a smart but sneaky guy lol

My Performabuilt "tagged" filter

Attachment 153144

Thanks brother - appreciate the info. The supercharger is on a 14-16 week lead time right now, so it's going to be some time before this project gets rolling. Good thing, because I hadn't budgeted for a converter, and this is stretching me thin.

Ahh, I see you got the same one! Yeah, I noticed a tag on mine from a different guy when I changed the fluid last year. I did the install when my OE trans burned up 3 & 4 at 103k miles in November of '20. Had it built knowing I'd hot rod the truck at some point in it's life - didn't expect it to be this soon.

Hoping I never have to send this trans back. He was pretty confident that I'd never break it, but that's when it was stock. I'll be out of warranty by this fall. I'm dreading separating this trans from the engine again. It absolutely SUCKS on the 900 series trucks. Whoever thought it was a good idea to put a bolt right up at the very top of the bellhousing is an a-hole. The worst engineering I've ever seen. It's as if they did it on purpose to punish mechanics ...

Thanks again - I'm going to go to Circle-D's site right now. :cheers:

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The gmt900 are a piece of cake, I just R/R'd one last night. Takes 20 min to drop it out.
Try removing a 6sp manual in a coyote mustang if you want some fun :)
The converter will be ok for a little while if the tune is setup right and not locking the converter while in boost.
it took me 5 weeks exactly to get the last 3 converters from Circle D.

Nothing is easy in the Northeast, especially after 15 years of road salt. Took me 2 weeks to R&R the trans / transfer case .... WITH a LIFT.

Yeah, I HATE modern vehicles. Every year I hate them more! I'm in the wrong line of business, lol. Thanks for the info.

Filled out the form on Circle D's site - just waiting for a response.:cheers:

Just found the email - they got back to me this AM. I didn't see it buried in the 300 emails I get every couple hours.

Looks like they recommend the 01-13-06-1B Pro Series 265mm billet triple disc. Sounds like exactly what I need. That just SMOKED my budget. Wow, stuff ain't cheap today! I remember when sinking $300 into a vehicle would completely transform it. Now headers cost 6x that! I suppose this stuff ain't getting any cheaper, so might as well get it over with. This truck is going to be pretty sweet when it's done. Thanks for your help, fellas.

Any tips for GMT 900 owners?

I have the 265mm triple disc 1a, which is tighter than the 1b. CircleD recommended the 1b to me as well. Have you ever lived with a loose converter? If you drive this thing a lot, you might want to consider the tighter convertor.

i went 1a 2600 stall and had no regrets at all

I'm not sure I completely understand the terminology. Loose as in it will flash to its stall RPM easily, like at part throttle? I've owned a few hotrodded vehicles over the years, but never played with stall converters before. I don't fully understand what "tight" and "loose" are.

In their email they made it sound like it will be perfect for a daily driver, but still hold up to my abuse in MA traffic, towing heavier than I should be at higher than normal speeds, coupled with full throttle launches while loaded and still survive a long time.