6.5 and 6L80

[afgunn]

If this is the wrong forum I apologize. Seems like a toss up to me.

I am interested in an allison or 6L80 transmission for my 6.5 in a couple of years after I rebuild the engine and make several power and durability improvements. It seems that the 6L80 would probably mate up and fit easier than the allison. Is the 6L80 about the same size as my 4L80? Will it bolt up to the 6.5? Seems it should. The 6L80 is rated for diesels at 300 bhp and 520 lb-ft. My 6.5 "Power Project" rebuild should be within those limits. I have a 10 page article on the 6L80 if anyone is interested.

Here are some interesting specs:
2006 Allison 1000
1st 3.10, 2nd 1.81, 3rd 1.41, 4th 1.00, 5th 0.71, 6th 0.61

2007 Hydra-Matic 6L80
1st 4.03, 2nd 2.36, 3rd 1.53, 4th 1.15, 5th 0.85, 6th 0.67

Check out 1st gear on the 6L80! Will definitely have to be careful when launching or you will burn the tires up! Might be a good opportunity for a 3.08 rearend!? The gear spacing on the 6L80 seems more like a manual 4 speed. Right now I am more inclined to the 6L80 than an allison. Any thoughts?! Allison vs 6L80 that is. Please no negativity. We are talking about projects and fun not work.

Anyone have any knowledge or experience with the 6L80 connecting to a 6.5? By the way here is a link for a stand-a-lone controller for the allison or 6L80 (thanks to Jim):
http://www.powertraincontrolsolutions.com/content-4.html


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[john8662]

Now we're talking!

Don't know a thing about this transmission, except now what you've posted, thanks.

I'd be interested in that 10 page article on it.

The OD ratio of that transmission is much taller (6th) than the 4L80E's 4th, but still not as tall as the Ally, I can live with that, hmm...

[afgunn]

For all here is the link to the 8 page manual:
cadillacfaq.com/stsfaq/tsb/data/tsb/05-07-30-023.pdf

It will be a couple of years or so but, I will continue to get info and post here on the feasability, ability and needs of coupling the 6L80 to the 6.5. The availability of the stand-a-lone TCM filled a big hole!

A wiikipedia revealed the following:
Applications:
2006 Chevrolet Corvette
2006 Cadillac XLR-V
2007- Cadillac STS
2007 Chevrolet Tahoe
2007 GMC Yukon
2007 Cadillac Escalade

So it first came out in 2005 (model 2006).

[Craig M]

Those are all gas powered vehicles. Will there be a problem getting a diesel converter?

[afgunn]

2007 Hydra-Matic 6L90 Transmission ( MYD )
Type: six speed RWD / AWD, electronically controlled automatic overdrive transmission with torque converter clutch. Clutch-to-clutch architecture, with integral Electro / Hydraulic Controls Module
Maximum engine power: 452 bhp ( 337 kW ), Diesel: 300bhp ( 223kW )
Maximum engine torque: 531 lb-ft ( 720 Nm ), Diesel: 520 lb-ft ( 705 Nm )
Maximum gearbox torque: 885 lb-ft ( 1200 Nm )

Available Control Features: Multiple Shift Patterns ( Selectable or Adaptive ); Driver Shift Control ( Tap Up / Tap Down ); Enhanced Performance Algorithm Shifting ( PAS II ); Next Generation Tow / Haul Mode; Engine Torque Management On All Shifts; Altitude and Temperature Compensation; Adaptive Shift Time; Neutral Idle; Reverse Lockout; Automatic Grade Braking

Of course this is info on the 6L90 (MYD). The 6L80 is MYC and I do not know if the Diesel HP and troque ratings are different or not. Unfortunately I left my "transmission folder" at home when I left for work but, I will check over the weekend. IIRC the data I have showed a 225 and 300mm torque converter. Maybe the 300 is for diesels!?

Check the 8 page manual on my previous post. It will give you a lot of info.
Also, I read today that the 6L80 is only slightly larger than the 4L80.

Very important! Does anyone have a buddy that gets Hot Rod Magazine? November 2005 is supposed to have an article on the 6L80. Let me know what Hot Rod has to say. I'll bet the hotrod community is wetting their pants over this 6 speed auto!

[afgunn]

OK! Here is the real reason to get a 6L80!

3.73 rear gear ratio:
4L80: 1st=2.48, 2nd=5.52, 3rd=3.73, 4th=2.8
Final Drive Ratio 1st=9.25, 2nd=5.52, 3rd=3.73, 4th=2.8

2.56 rear gear ratio:
6L80: 1st=4.027, 2nd=2.364, 3rd=1.532, 4th=1.152, 5th=0.852, 6th=0.667
Final Drive Ratio: 1st=10.31, 2nd=6.05, 3rd=3.92, 4th=2.95, 5th=2.18, 6th=1.71

And note that 1st gear with the 2.56 and 6L80 is lower than the 3.73 and 4L80. And what about the topend!? Also, Driver Shift Control (DSC) which allows the driver to manually shift (select) gears. And closer gearing, and ..., and...

[Bnave95]

With the above,what would the rpm's be at? Is it possable to rear gear to low and have eng. rpm's to low in a heavy truck?

[noelb]

I spent some time recently working out RPM's at different speeds with different gearing and tyres. In Australia towing is restricted to 100kp/h (62.5Mp/h) I found that 3.73 gears and 245/75 tyres seemed to put the revs about perfect. 1950 rpms at 100kp/h in OD and 2500-2700 in 3rd for towing up steep grades at 90-100 kp/h. Gearing any taller would give better economy at much higher speeds but here in Australia the Tickets for Speeding can be in excess of $300 AUD. Plus get caught 4 times and loose your licence for 6 months.

Don't get me wrong I love the idea of a 6L80 trans and even asked the question to my Auto Trans Shop a few weeks back as I was dreaming about it myself. The info I have seen so far is all good info. I'm not totally sure it can be done successfully though on the back of a 6.5.

There is a place in Australia that has developed a Full Manual valve body (no need for computer) to convert electronic 4L80E's - perhaps it is not much more work to do the 6L80.

[afgunn]

Ok, thanks to all who posted - a lot of good helpful info! I am about 99% sure that I will go with an Allison 6 speed for the strength (360hp and 520 ft-lbs), durability, it bolts to the 6.2/6.5, fits in the trans tunnel and the fact that is is made and geared for a diesel! And, for the final reason:

RPM = MPH x Final Gear Ratio x 336 / tire diameter
= 70 x (3.73 x 0.61) x 336 / 30.6
= 70 x 2.28 x 336 / 30.6
= 1749 RPM

And yes you would need a stand-alone controller because the TCM of the Allison is not made to communicate with the 6.5 PCM. And this one looks like a good one:

http://www.powertraincontrolsolutions.com/content-4.html