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Discussion Starter · #1 ·
Newbie here. Have a '46 Chevy 1-1/2 ton chassis I am going to mod with the beloved 4BTA but would like to back it up with a newer 6-speed automatic. The GM 6L90 is well within the torque specs and is a "double overdrive" (I am going for long-haul MPG). Has anyone gone this route or looked into this tranny? Other reasons it has me considering is fairly light weight (compared to an Allison) the built in controller and availability of aftermarket kits that should make for a (reasonably) smooth transplant (yeah, right). Also thought about the brand new (2010) Furd six-speed TorqShift, but the adapter & controller seem to be significant issues. Thanks in advance for any wisdom.
 

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Physically bolting the 6L90 to the 4bt is simple - you can use a bread van adapter or, better yet, the Destroked adapter.

The electronics are a whole 'nother can of worms. Yes, it has an internal TCM. Problem is, it gets ALL of it's operating information via a high speed GMLAN interface. You aren't gonna just hook up a TPS and be on your merry way with this one.
 

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Discussion Starter · #4 ·
No telling when, but I have contacted two aftermarket suppliers who are "working on" the programming & harness kits for the GM and the Ford 6-speeds. Sounded like they could be out around the end of the year. Given fuel prices, there is huge interest in both of these trannies as transplants. One was Destroked but I don't have my notes handy on the other.
 

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No pricing eh? To me, that means it's gonna be lots of $$$.
 

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anyway, the 6L90 seems to be a better choice than the torqshift... now it seems to be more matter of time to see somebody coming with one of those aftermarket standalone auxiliary modules to fool the tcm...
 

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I've been in constant contact with 3 different companies about making a controller for the 6L90 trannies for around 2 years now. I get the same answer everytime I contact these companies "were working on it" so I ask any idea when it may be ready "were not sure should be within 6 months". The last time I talked to them all was about 3 months ago and none of them are any further along than before.

I've seen 2 companies complete the 6l90 conversion one was mast motorsports I think and they only did it by swapping in the donor motor it was originally bolted to which in my opinion is easy. The other company is true blue motorsports that does a true conversion for trail blazers but they still get all the data from the trailblazers factory engine, they just use a couple boxes to allow the trailblazer engine to talk to the 6l90.

I have a feeling its gonna be a long while till we see anyone with a true standalone for the 6l90's although I do think this will have to happen eventually since it seems all the new transmissions are going to this clutch to clutch style trans.
 

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Discussion Starter · #9 ·
Thanks for the input and Roger the same story. I have been getting the same thing. They all say they are inundated with calls about both the GM and the new Ford 6-speed trannies and swear they scrambling to work out solutions, but so far...nada. They must be having fits hacking the coding that lets these units talk to an engine. But since it could be a year before I have to make a final call on my trans choice, I may just keep my fingers crossed till then. I am really hoping to install an auto that has the kind of overdrive benefits (MPG) these units offer.
 

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If you're wanting a 6spd with good ratios I can recommend what I had planned to do a while back. I was going to run a 4l80e with gear vendors behind it and use a pcs controller to make it all shift quit sticky since the pcs can control up to 6 gears. Just a thought.
 

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Unfortunately, it would be cheaper to run an Allison, and you would have a much stronger trans as well...
 

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Discussion Starter · #12 ·
Hey Max --- I am definitely still considering an Allison. In fact, just today I came across 1000 PK Series 6-speed with 19K miles for $1500 bucks. I know it can be bolted up, but still need to find out about a stand alone controller that will talk to the 4BT. Will be talking to the local Allison folks tomorrow to see what they can tell me for a start.
 

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Hey Max --- I am definitely still considering an Allison. In fact, just today I came across 1000 PK Series 6-speed with 19K miles for $1500 bucks. I know it can be bolted up, but still need to find out about a stand alone controller that will talk to the 4BT.
Did you read this thread: http://www.4btswaps.com/forum/showthread.php?15428-The-complete-Allison-1000-2000-2400-info-and-swap-guide-thread

Will be talking to the local Allison folks tomorrow to see what they can tell me for a start.
Good luck getting answers from those guys. If it isn't an OE app they wont even want to talk to you.
 

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Discussion Starter · #14 · (Edited)
Ouch! Trying to read through that guide made my brain hurt. Just put money down on a 4BTAA that has an Allison 545 attached. Just may live with that until some Guru works out a magic box for the OD units. Back to trying to find a taller rear end. (or a 653 swap for the extra gear?)
 

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Anyone here using a 6L80 or 6L90 with a 4BT? I have a NV4500 behind mine and I'm getting a little tired with the wide jumps between gears the loss of speed/boost during shifts.
 

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Seems like member Old Roofer is using a 6L80e on his truck. He also opted for Rube Bonet's flex plate adapter which is about 100 times stronger than the OEM wave ring. Seems like member F100 Today is using that transmission also. You'd also have to figure on what block adapter to use. The OEM Cummins GM plate is a tilted design. There are aftermarket units that don't tilt.
 

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Just stumbled on this thread. It's an old thread but I'm running a 6L80e behind my 4bt and just love it. If anyone needs details I can offer them up

A couple of things that you will need. 1) a tcm-2650 from zero gravity performance. 2) tuning software (HP / Efi live) to get to the shift tables and tune if for proper shifting 3) some minor mods to the flexplate for the standard gm setup 4) a 1/8" spacer between the adapter and the bell housing for proper spacing.

All you need electrically is a throttle position input and an rpm input. You will need computer knowledge to get the software setup and tune the shift points.
 

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Tango88,

Dana 80’s and Rockwell rear axles come with higher ratios with 10 on 7.25” wheel bolt pattern. GM P series trucks come with these, as well as allow disc brake spindles/hubs to fit older GM trucks two ton front axles, keeping tires inside fenders, although factory wide front fenders do exist.

Ed in CO
 

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Just stumbled on this thread. It's an old thread but I'm running a 6L80e behind my 4bt and just love it. If anyone needs details I can offer them up

A couple of things that you will need. 1) a tcm-2650 from zero gravity performance. 2) tuning software (HP / Efi live) to get to the shift tables and tune if for proper shifting 3) some minor mods to the flexplate for the standard gm setup 4) a 1/8" spacer between the adapter and the bell housing for proper spacing.

All you need electrically is a throttle position input and an rpm input. You will need computer knowledge to get the software setup and tune the shift points.
im working on a swap in an 08 caddilac right now and am at a loss for the wiring, where do you get a tps signal from the accelerator pedal? and the rpm signal as well, what about the reverse lights and brake pedal inputs. thanks
 
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