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maxxTORQUE article on the A Team Turbo

When you are grade braking the TCC is usually unlocked. The overrun clutches in 2nd gear are very small. They only hold the vehicle back in manual 2nd and a sprag clutch will lockup for forward motion with engine power. Cut power and 2nd gear would normally freewheel except for the overrun clutches in manual 2nd.

You add load to the clutches with the TCC locked in. There is a point they don't hold anymore at higher RPM. Once they slip they burn up quickly.

So you do not want to hold it back with the tcc override switch on. Solution is well adjusted rear brakes, good trailer brakes, and possible proportioning valve update if you have a burb.

The slip you feel when the TCC should be locking up could be from valve body wear as the TCC valve body is known to wear out and cause the TCC to slip. This may be the repair you need now before the converter clutch slips and burns up requiring a full rebuild.

The solution to the TCC override switch is a better turbo so you are not at higher RPM and need the TCC locked up for 1-2 MPH extra. You have the power with a bigger turbo to slip the converter and get moving rather than just waste power in the unlocked converter. The TCC override will help when the TCC is normally in as the computer doesn't hold 100% most of the time. It is programmed to slip some for smoothness and maybe cooling oil flow of the converter. Maybe add some MPG by reducing the slight slip by going 100% locked? The bigger turbo made a TCC override useless as it no longer provided a MPH gain.

The TCC override switch is a band aid for the engine getting choked up at higher RPM. Factory turbo's cause you to loose power to where the TCC becomes a power robing component because you are not making enough power at higher RPM to have more torque out of the converter than you are putting in due to slippage and resulting heat loss. More power unlocked means you get more torque out of the converter than you loose in heat generation.

Trans rebuilds cost me $995 in and out plus hard parts if any. So I can't see spending $1,000 for a high end converter that will take the extra abuse. My rebuilt trans handled 50K of this abuse although the 2nd gear overruns went out in the first 15K. The TCC clutch burned up at 50K and required a rebuild. Factory rebuilt converters is all I am running.
 
WarWagon, VERY nice article and very well written. You have to be the number one abuser of the 6.5 :)
 
Thanks for your reply WW. I need to clarify part of my question, but if you feel this needs to be in a different thread I'll start one.

The vehicle in question is the 94 K2500 in my sig line. The slip during TC lockup is new as of this summer (after I swapped turbos is when I first noticed it) and only lasts very briefly. As the lockup happens the motor revs for just a second, or less, then is locked. I don't know how many miles on the tranny, but the odometer is 241K and I have the vehicle history available to me from about 160K. The guy I got it from did not do any tranny work, so I'm assuming this tranny is still all original, except for the three plug-n-play valves I replaced when I went to a deeper tranny pan.

So, from what you're saying I should check out the valve body. Makes sense to me considering the possible miles on it. I have no experience with auto trannies, except for what I did when I swapped out for the deeper pan, so I'll have to defer to those with the experience.

I have been searching for ways to improve the brakes, but have not found much for the 8600 GVW and up trucks. I did find someone who went to the DMax front brakes, bigger pads and two pistons per caliper. I have picked up the complete front DMax parts from a wrecking yard, but it will be sometime this winter before I have the time to work on retro fitting them.

The rig still has the stock tune, but this summer I did replace the turbo with a used Holset HX53W from an 01 Cummins. I have noticed some improvement in the way the motor runs, and an increase in EGT temps.

Again, since this isn't ATT centered, (towing centered though) if you prefer this to be in a different thread let me know and I'll get one started.

Thank you!!

Don
 
sshewins said:
I'd say there is about a twenty-way tie for first place. :)
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I have got to hold the title for the most blown up/completely ruined 6.5's in one year that STILL ran before they were pulled. Even if they only hit on 7 of 8... (Cracks aside of course.)
 
As far as the transmission, tap the brakes and see if the engine free revs. Tapping the brake will unlock the TCC. You can use the override switch, but, suspect it may have issues. (Wired wrong, bad ground, etc.) If the engine doesn't free rev for the TCC then it is slipping a clutch pack/band. Likely for the 4th, OD combo. It can slip a clutch pack when the TCC locks up.

Slipping means the trans will burn up soon. The clutches are designed to grab rather quickly and not slip. There isn't any mass to take the heat from slipping - trans oil just boils.

Any codes in the computer?
 
handcannon said:
I have been searching for ways to improve the brakes, but have not found much for the 8600 GVW and up trucks. I did find someone who went to the DMax front brakes, bigger pads and two pistons per caliper. I have picked up the complete front DMax parts from a wrecking yard, but it will be sometime this winter before I have the time to work on retro fitting them.
Click to expand...

Please keep us up to date on this one. I had no idea better calipers could fit our front ends!
 
I just bought a complete 6.5 witha broken crank off a friend, he bought the truck to do a cummins swap. He called me knowing i love the 6.5. He said "I have a motor for you. I'm not familiar with the 6.5 but the turbo looks much larger then i remember". so i went to look. as soon as i opened the hood i knew what it was, ATT. I said what you want for it he replies $500 motor, trans, transfer, comp, turbo. He delivered it the next day about noon. I had the turbo on the two door by 2pm then sold the trans the next day for $700. so i got paid $200 to put the ATT on my truck. I hear you calling me names!

I have not done milage yet but wow did it free up the low end. the boost is way lower then i am used to but it has a lot more power. It smokes a lot at lower rpms and i have been told its cause of the Heath GL4 tune for the GM6(GM4 front and center,GM8 exhaust side) I was running. I called Bill and am sending back my chip for reprograming to his ATT tune. I'll let you know.
 
vegtech said:
I just bought a complete 6.5 witha broken crank off a friend, he bought the truck to do a cummins swap. He called me knowing i love the 6.5. He said "I have a motor for you. I'm not familiar with the 6.5 but the turbo looks much larger then i remember". so i went to look. as soon as i opened the hood i knew what it was, ATT. I said what you want for it he replies $500 motor, trans, transfer, comp, turbo. He delivered it the next day about noon. I had the turbo on the two door by 2pm then sold the trans the next day for $700. so i got paid $200 to put the ATT on my truck. I hear you calling me names!

I have not done milage yet but wow did it free up the low end. the boost is way lower then i am used to but it has a lot more power. It smokes a lot at lower rpms and i have been told its cause of the Heath GL4 tune for the GM6(GM4 front and center,GM8 exhaust side) I was running. I called Bill and am sending back my chip for reprograming to his ATT tune. I'll let you know.
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I think you will love it. I sent mine back to Bill and am pretty happy with it. A little more smoke at low rpm's if you get on it kind of hard, but I well worth it to have him reflash it. Can't wait to hear what you think.
 
vegtech said:
I have not done milage yet but wow did it free up the low end. the boost is way lower then i am used to but it has a lot more power. It smokes a lot at lower rpms and i have been told its cause of the Heath GL4 tune for the GM6(GM4 front and center,GM8 exhaust side) I was running. I called Bill and am sending back my chip for reprograming to his ATT tune. I'll let you know.
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Be interesting to see if Bill's shop is doing any better. Last time I spoke to them they were of the opinion the ATT was to large for the 6.5 and couldn't figure out how to 'cure' the smoke problems they were having with the ATT and their tunes. I hope their attitude has improved toward the ATT... But just something to keep in mind.

Several other folks are doing tunes for the ATT and the results are getting impressive and nearly smoke free. FWIW my 1993 and ATT equipped ride with the 'tune free' DB-2 can be adjusted for low to no smoke. It can also pour it on when you really turn it up. Tested at altitude and sea level.
 
WarWagon said:
Be interesting to see if Bill's shop is doing any better. Last time I spoke to them they were of the opinion the ATT was to large for the 6.5 and couldn't figure out how to 'cure' the smoke problems they were having with the ATT and their tunes. I hope their attitude has improved toward the ATT... But just something to keep in mind.

Several other folks are doing tunes for the ATT and the results are getting impressive and nearly smoke free. FWIW my 1993 and ATT equipped ride with the 'tune free' DB-2 can be adjusted for low to no smoke. It can also pour it on when you really turn it up. Tested at altitude and sea level.
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I was not sure about sending it back to him(I had the GLE for my GM8) after a couple conversations with him. But, I figured for what he said he would charge me to reflash, I would give him a shot. It smoked quite a bit off idle if you gave it 1/4 throttle or more. But the power was really good. It has toned down on the smoke over the next week or so. Really not too much now unless you just stomp it from a stop. Power is awesome and the boost comes up real quick compared to the stock or GLE program I had. And I really like the way he made the trans. shift. Bill definitely exceeded my expectations since he expressed his belief of it being to big of a turbo for our trucks.
 
Bill still not 100% "sold " on the idea told me for a long time the turbo is too big, it took some time to get the tune where it is now.

I've got a 90 GMC short box step-side C1500 project in mind for an old 6.2 engine swap out the 4.3L V-6 gasser, that would be sweet with turbo; Bill thinks the GM turbo would be the ticket for that (ATT is too big :) ), I'll try both ATT and GM-turbo on it with the mech IP; always gonna be some disagreement 2 gear-heads in same garage, plus since ATT wasn't invented his shop & his intellectual capitol is geared up for sales volume, commercially it makes more sense to go with where he has invested his time in GM-X tuning. Rework if the tune doesn't work due to a vehicle specific anomaly that doesn't work with the ATT hard to diagnose if having to build a tune to match that vehicles unique characteristics also another reason for Bill to have reservations about the applicability of it to the 6.5. That said from what I've seen the ATT successes far outweigh the ones that have reported issues with it; and other than the folks that just gave up on trying to find the issue the ones where ATT was a challenge, eventually the vehicle anomaly had been identified & corrected to a successful outcome.

I think 99GMC you may be seeing some of the tuning results from tweaking on mine. Still more to go I think personally but all in good time.

Bill sort of fits me in between projects. Bill got a bad taste from the ATT when it was combined with the hatchet job that was done on 635s truck by former employee Ian there, the injectors were bad and Ian fed the turbo hard things that it could not digest, which smoked (BADLY) after all that; and led to Bill saying "see I told you" partly based also on Bill's experiments with the Peninsular big turbo. I think Paveltoz has that turbo now but with blending that had to be done to fix the damage to the turbo it is not exact as the turbos sold new and unblended.
 
Yeah, I've still got that ATT and I'm still waiting on the used but known good housing to arrive so I can compare it to mine to ascertain if there's damage or not from being "Ianized."
I stopped holding my breath waiting for it to arrive though....
 
Turbine Doc said:
When I posted years ago gaining 2 mpg with mine even @ 75mph avg speed range 440 miles up from 385 with the GM-8 & 26 gal tank topped off to sputtering out of fuel, measured on same run GA to MS measured same trip 16x a month for nearly 2 years I was told it could not happen, then to add in my burb @ 70 mph avg gaining 3 mpg when I put the ATT on it; it is nice to see someone else with appreciable mpg gains as well.
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Man, I would LOVE to get a consistent 20-21 MPG highway with my '98 K2500 Burb just from dropping on the ATT. Throw in an optimal MPG OBD-II tune from Dennis and Co. with it and the right set-up on the injectors and I think a consistent 23-25 MPG at 75-80 on the Interstate is well within the realm of reality. Think about that: Eight people, luggage and an honest 900-950 mile cruising range with the 'Burb's 42 gallon tank. Add the pickup's 36 gallon tank along side the frame rail as the Aux tank, and Lincoln, NE to L.A. on one fueling becomes a doable adventure!
 
Get your tanks sucked dry just once... Fill ups will take 2 cards and 4 swipes...
 
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