4BT + 6L80e

TBSS has not replied to email for four weeks now regarding a transfer case adapter so time to just make my own. I thought that is who built the adapter for Aventr but I may be in error and he had it made locally. In any case, my preference is to modify something I can find on the shelf rather than start from scratch. Both advance adapters and Novak look like they have something I can modify. Waiting to confirm some dimensions now to proceed.

IIRC the transfer case adapter was built by tbss. It was the 6l80e output shaft that he had turned locally to match the xfer case.

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We just made one tried modifying off the shelf piece but pilot diameter totally wrong but more importantly flange is way too small diameter on other adapters to mate with the stock H3 case bolt pattern.

So whats the bolt circle on the H3 transfer case? I get a 6.81" bolt circle on a standard 6L80e factory adapter.

So Novak's adapter is only 3 1/4" deep. Seems like I could bolt up a 1/2" flange right to it with the correct pilot and bolt circle and be golden. I talked to Novak Friday and they would sell just the adapter shown in this pic.

Reverse engineering the flange patterns. I have an idea for a fabricated adapter, next step is to take this and complete a cad drawing. I measured all of the bolts with calipers and calculated the bolt circle and indexing. To test the calculations, I used some card stock and plotted the results in CAD and printed to scale. I then cut out the templates and laid them on the respective units. Keep in mind the indexing is looking at the xfer case and transmission. These will need to be mirrored to be laid out on the companion flanges.







I still need to fab a foot to mount to the crossmember and haven't decided if this will be welded to the spool or possibly just bolted on separately.

Very cool, I will be watching closely!

If you want to prototype it...I know some 3D printer guys that can crank out a plastic one. Then you can test fit it...tweak it...make adjustments...then make the real deal.

Im trying to upload a picture of the one we just made but for some reason it says the picture has finished uploading but does not appear in the post editor?

4speedfunk said:

If you want to prototype it...I know some 3D printer guys that can crank out a plastic one. Then you can test fit it...tweak it...make adjustments...then make the real deal.

Click to expand...

This is the beauty of 3D printing if you have one large enough!

I was thinking that you might be able to use one for a number of projects that have been talking about here for a long time - this is however not one of those applications that I was thinking of!

Good call CJ

atvspeed4 said:

Im trying to upload a picture of the one we just made but for some reason it says the picture has finished uploading but does not appear in the post editor?

Click to expand...

ost: Make it happen

RamRod said:

This is the beauty of 3D printing if you have one large enough!

I was thinking that you might be able to use one for a number of projects that have been talking about here for a long time - this is however not one of those applications that I was thinking of!

Good call CJ

Click to expand...

We have one and use it quite often for prototyping but it is not a precision match to your CAD drawing like machining metal. There are so many variables printing plastic it can only give you a general idea if your concept works or fits in the space constraints.

Hopefully this posts from Tapatalk

yup I can see it!

Did you confirm that the TCS controller actually will communicate with our H3 TCCM over CAN to receive signal that it is in 4LO or with the BCM to know when you shift into reverse? What are you doing about aligning the shifter pattern in dash cluster with programming so that PRND321 aligns with PRNDM21?

These are the issues that led us to work with a custom programmer because we were told the TCS controller would not work for the H3 application without installing a custom 4LO momentary switch like the old transfercases had. Let us know if you find a work around as that controller would be much easier to get!

CaseyS did you make headway on this project? I've got some questions on what you figured out with the torque converter/flexplate combo.
Thx

[url=https://imgur.com/lvsE7lT] [/URL]

This project is not dead! I've been out of circulation for a while.

I have the front end worked out. This took some modifications to the flexplate. The torque converter bolt circle is slightly larger than the 4l60 so a quick buzz with a carbide burr to oval the holes fixed that. Second, the snout of the torque converter bottomed out on a step in the female side of the centerbore in the flexplate. When the crank was in for balancing, I had the machine shop remove the step so the centerbore goes all the way through. I am still plenty far enough from the snout bottoming on the crank.

For the back end I have a novak 6L81 universal adapter and I am getting a custom adapter donut to mount it all up. The novak unit is 3.25" long so a 075" thick plate with the proper drilling and a centering ring will allow it to all bolt up. I had previously had the 6l80e output shaft turned down to a 27 spline to fit the transfer case.

The wiring has a few challenges that I didn't expect from early research but no dealbreakers. Im using the PCS 2650 standalone and in the process of planning my wiring harness rework. The first major item is that the shift linkage on the 6 cannot mount the shift position indicator switches that the H3 uses. The indicator basically has 3 major circuits 1) a park/neutral switch for safe starting of the vehicle, 2) a reverse contact to power backup lights, and 3) a set of 4 switches used to encode the shifter position which is then communicated to the instrument panel. The 6 has an internal park neutral switch but its not an isolated contact. This will require a relay to isolate the signal. The 2650 has a reverse output which again is not isolated so a second relay will be required for reverse. The 4 encoded switches I'm afraid I will not be able to replicate. This means I will lose My PRNDL321 indication on the console. There are aftermarket gear indicators that plug right into the 2650 harness so if I want I will be able to display what I need, albiet not in an OEM fashion like I would prefer. Other than that I am just planning optimal routing now and harness work should start this weekend.

So glad to see this project is still kicking like a champ!

Casey...I still have your t-case adapter. You got that issue solved?

I'll try to update this in chronological order as its been a while since I've updated. Been real busy with life and am back trying to get this project completed. From the earlier posts, I got a friend to 3d print me a prototype adapter flange. His printer platen wasn't big enough to do in one piece so you can see its split in two halves. This is it bolted to the transfer case.



I ended up finding an orientation to get six studs in instead of the five. This adapter bolts to the transfer case with M10x25 socket head screws and you just move the transfer case studs to the flange. I kept enough material on the flange where they are counter sunk so you have to shave the bolts head by 1mm to clear flush. Here is the finished flange. I had the same friend make me a solid model file and I sent it of to Xometry. Cost was less that $250 for the flange and a centering ring



And bolted up with one of the studs installed. Note the second piece to this is a centering ring. This will keep everything centered when bolted up. It was much simpler to machine these to parts separate than to try and make a complex assembly as one piece.



The "foot" for the mount is fabricated from a simple piece of 2"x3"x1/4" steel angle and is clamped in with the lower two studs on the flange. I do not have a good isolated shot of the foot.

For the isolation mount, I first had tried and assembly with a stack of generic urethane disks. My original foot was bolted to the part of the novak flange specifically made for that purpose but there were two things I didn't like about it. First it interfered with the lower two bolts so the transfer case was only held on with four bolts to the adapter. Second, I didn't like how secure the through bolt ended up and because of the bolt placement, made it very difficult to access. So I decided to just pour a monoblock urethane mount.

I made a mold out of wood and mounted the bolt assemblies in it. The stack from inner to outer is bolt, fender washer, nut, fender washer, flange, nut. The innermost fender washer is clamped into place by the nut which will help secure anything from rotating during tightening, and secondly the fender washer will give a nice big surface area to spread any tension force through the mount. In addition, the way this is stacked, when the mount is bolted to the flange, the end nut will be clamping against the fender washer and nut resulting in only bolt tension and no preload tension trying to pull the bolt out of the mount just due to being bolted in.






And here is everything bolted up




This moved the bolts slightly forward in the crossmember so i had to extended the slots forward about a half inch.



Overall this made a clean setup. I'll report back with some results once some miles get logged. Hopefully by early spring.

It's great to see some updates about this.

Nice! Did you do a SA swap in your rig?

What's the weight difference of the two engines?

I've put about 100 miles on the setup so far and got to tell you this thing is slick. Miles ahead of the 4 speed. I've got a rough shift schedule pretty close with a few spots I want to tweak just a little but its 100% driveable. I have it set to lockup in 5th and 6th. It runs locked 5th around city streets and only kicks to 6th above about 60mph. At that point I'm about 1500 rpm.

The very nice thing about using OEM software is the torque converter lock can be set on a similar schedule to the shift points based on throttle position. My aftermarket 4l60e controller would only lock/unlock at a single speed.

I have the mechanics, electrical and programming figured out for tap shifting. I just need to figure out how and where to tap. I can shift to what was D3 on the shifter to set tap mode but then need to figure out if I can mount buttons on the shifter or the console or the steering wheel somewhere. The other path is just replacing the shifter with one that either has mounted buttons or one that moves to the right and you bang the whole stick forward or back to shift. I wish tahoes had an oem floor shifter that would drop in.

I'll try to get some video later in the week.

Malibu shifter…


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