BLOWN TORQUE CONVERTER

I own a 02 Chevy Tahoe (2WD) with a 5.3 Vortec, now I just installed a 16" 3rd Coast lift kit, a SCT Flashpaq and have KMC 20/12.50 Rockstars with 40" Toyo Open Country M/t's. I was told that I should install 4:88 gears once I got the lift, so I did. After I drove the truck from Houston to San Antonio, 6 (yes 6) days later my tranny COMPLETELY blew out! After a COMPLETE rebuild my tranny shop suggested that I should have extended my driveshaft and recommended HIGHER gears and a Double Carden U Joint, so I drove the Tahoe back to Houston and had them extend the Driveshaft as recommended, they installed an extended dshaft and new u joints, they did NOT recommend a DC joint.

Now when I drove back again from Houston to San Antonio, the torq converter BLEW OUT! Yes thats the BRAND NEW torque converter!

OK EXPERT'S Heres your question! FINALLY!
The tranny shop said that they will wty the burned out torque conv, but they STRONGLY recommend that I get 5;38 gears installed instead of the 4:88's AND that I have an "EXTERNAL" tranny cooler, due to the size of the toyo's (40)!
WHAT SHOULD I DO!
This truck will NEVER go off road, it will never go past 70mph, and I am totally confused
Did the off road shop put the WRONG gears in?
Is the tranny shop wrong about a external cooler!

I appreciate ALL your help because I'm about to pull a Thelma and Louise in my tahoe!
Feel free to contact me directly if there is someting I left out.  

Heat is the #1 killer of transmissions, and 40's can generate a lot of heat!

An external cooler for the trans is a really good idea.

I would have recommended that you go with 5.13's or 5.38's from the start, but for what you are doing I'm not convinced that 4.88's are what's killing the trans.

What it really sounds like is that it was the first transmissions time to go, then  you got a faulty TC after the rebuild.

I would put a cooler on it and go from there.  
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Long Travel 4WD - The best of Both Worlds

Questions? Comments? Concerns? PM Me!

WOW I totally think you are on the MONEY! I appreciate your opinion and I too think that I had a defective t/c. I do kinda have a lil problem with the first tranny going out ONLY 6 days after the lift was installed, I NEVER had any issues with it before the lift, no kidding!

The off road shop said the tranny cooler IS NOT a bad idea, but also not something that is life or death either, they said the have installed VERY few of those.

They also said that the 4.88's are perfect for the Tahoe even with the 40's.  They  said they usually use 5.13/5.38 on 44's NOT 40's

Also said the 4.88 parts are smaller than stock, and the smaller you go...may not be better for me?

Any thoughts on that?  

Did you get it fixed yet?

On the smaller statement... Yes and no. No the ring and pinion don't get any smaller. But the teeth do. As you cram more teeth into the same area they get thinner. I've never seen this as an issue though.  
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Long Travel 4WD - The best of Both Worlds

Questions? Comments? Concerns? PM Me!