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6l90 behind a 6.5

ak diesel driver

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So a buddy of mine is getting ready to put a 6l90 behind his 93 6.5. Says he'll be able to tune it with hptuners. Evidently it about 2 1/2" shorter than the 4l80 but he thinks between his 2 slip yolks he won't have to lengthen the rear shaft but will probably have to shorten the front. The other hurdle is torque converter heights are different but he has 2 options. 1 is a custom height converter the other is a shim for between the engine and bell housing which someone already makes. Should be interesting to see how it comes out
 

THEFERMANATOR

FRANKENBURBAN
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It takes alot more than just hptuners to make a t43 work. The 6l80/6l90 uses a T43 TCM that is mounted to the valve body. It uses all high speed GMLAN for data coms. There's only a few wires that even run to it. The only way I know to make one work is to either use a compatible GM ECM from a gen 4 or 5 LS, or PCS makes a gateway that converts other signals into HS GMLAN that the T43 can understand. Unless there has been monumental advances at HPTuners in the last year on T43 development(I doubt because EFILIVE's board would be lit up with request's for it if HP had it), he's going to run into a $900 hurdle for the PCS 2650 gateway box and harness.
 

Rockabillyrat

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THEFERMANATOR is correct. You will need the PCS box to make it all work. You can do the tuning with HP tuners. But need the PCS to make everything talk to each other.

They put the 6l90 behind the duramax in some of the Van's. I believe the LMLs. I thought someone said that converter will work on a 6.5 application. But don't hold me to it. John at quadstar is doing a 6l90 swap and has the converter figured out. He might be able to lead you in the right direction with that.
 

ak diesel driver

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So he's working with a guy from Arizona on this. And one of the things he got from him is basically a gateway module with wiring harness and switches. $875.
 

THEFERMANATOR

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So he's working with a guy from Arizona on this. And one of the things he got from him is basically a gateway module with wiring harness and switches. $875.
Thats the pcs 2650. With that he shouldn't need HPTuners as it will take whatever signals you give it and modify them via graphs to whatever you want them to be. You could set it so the TPS is outputting 50%, but make it tell the trans it's 30 or 70%. You can do the same thing with all the inputs from what I found when I looked in to it. And it was the lgh van that got the 6l90 behind the Duramax. The lml was the 397hp truck version, lgh was the detuned commercial version, and it started in 2010 in the vans.
 
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ak diesel driver

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So it turns out that he's swapping the 6l90 for a 6l80. The output shaft is larger and would force him to use the T-case from the dmax, I think he said it was a 261. Also it turns out the guy in AZ is a retired GM engineer and knows his stuff on the 6l80
 

ak diesel driver

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So a small update he was trying to decide whether to go with the spacer kit or the TC. He is going to be getting the TC turns out it already a performance built TC.
 

quadstar87

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Thats the pcs 2650. With that he shouldn't need HPTuners as it will take whatever signals you give it and modify them via graphs to whatever you want them to be. You could set it so the TPS is outputting 50%, but make it tell the trans it's 30 or 70%. You can do the same thing with all the inputs from what I found when I looked in to it. And it was the lgh van that got the 6l90 behind the Duramax. The lml was the 397hp truck version, lgh was the detuned commercial version, and it started in 2010 in the vans.
The PCS box is just a passthru to take your analog inputs and put them on the bus so the trans can read them. All your 'TUNING' is done to the transmission's valve body TCM via HPTuners. Also takes other things like switch inputs for profile switching, tap shifting, converter lockup, etc. Good news is you don't need to use a license since the trans has no VIN. HPT MVPI2 is so cost effective that anyone who's doing this swap shouldn't care about the price.

I'm not making this up - I have one bolted up on the shop floor and flashed the TCM already.
 

quadstar87

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You can swap the input shaft from a 261 into a 241 case to bolt it up behind a 29 spline output. Or buy an input from Dodge as they used a 29 spline output when it was behind the Cummins.
Only part I couldn't figure out was the BW-4401 TCase like I have on the '98. Other than drawing up the input and having it made new, there wasn't a solution I could find.
 

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Only part I couldn't figure out was the BW-4401 TCase like I have on the '98. Other than drawing up the input and having it made new, there wasn't a solution I could find.
The Borg Warner cases were limited. Not sure if they were ever used by Ford or not as they also used a 29 spline. And I had read when the 2650 1st came out it was capable of manipulating the outputs that it switched to outputs from a posting by somebody at PCS.
 

ak diesel driver

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So he down to the final tune adjustments, he really likes it a lot. We were discussing his double brake tap feature where the transmission will try to maintain a certain vehicle speed and I mentioned an exhaust brake would be an ideal combo with that feature. He wanted me to ask if anyone has used one on there 6.5 and if it worked well or not.
 

Will L.

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A guy I worked with used one on his 97 manual trans c3500, he loved it.
Then I put one on my 99 c3500srw with 4l80 and it was nice for towing going downhill. But I sold that truck when I got my hummer and it was only on there 15,000 miles or so. I may have done the next owner wrong by it because the over run clutchseem to die young from it just like manual locking the tc.

IDK if there is a good fix for that or not. If so I would love to know for when it’s time to redo my trans. Solve that issue and I will put both on the hummer. Not sure it will do as good with the 18:1 now, thinking about it.
 

FellowTraveler

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A guy I worked with used one on his 97 manual trans c3500, he loved it.
Then I put one on my 99 c3500srw with 4l80 and it was nice for towing going downhill. But I sold that truck when I got my hummer and it was only on there 15,000 miles or so. I may have done the next owner wrong by it because the over run clutchseem to die young from it just like manual locking the tc.

IDK if there is a good fix for that or not. If so I would love to know for when it’s time to redo my trans. Solve that issue and I will put both on the hummer. Not sure it will do as good with the 18:1 now, thinking about it.
If I remember from this ole dust bin I call my memory there was some discussion on using exhaust brake with 4L80e in that the trans could not handle it, I'm thinking FERM has pointed this out too......
 

Will L.

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Yeah, mentioned the 4l80 as a question for me but also don’t know if the 6l90 suffers same issue. But no issues I know of on the 6.5 itself. The entire engine is operating normal just being starved of fuel at higher rpm. In gassers you can have lean fueling issues but in a diesel, it just cant supply the power.

You do get more soot build up in the exhaust in front of the brake device. Like if you see the videos where an idiot hold a rag on the tailpipe then lets it go after a couple seconds- just not as bad. So if he is running a vvt not a good idea. Mounted right off the turbo gives better performance but far enough away to not let the soot impede the turbine. As to if he has a soot trap in his exhaust- that could be an issue.
 
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