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Old 09-30-2010, 06:39 AM
Sonofagun12G Sonofagun12G is offline
Join Date: Sep 2010
Location: Sunshine Coast Qld Australia
Posts: 2
Default Will a 6 speed Allison fit a 6.5 v8

Hi All, Andy from the Sunshine Coast ,Australia, here. I am a 59 year old master tradesman electrician, and have played with vehicles (Land Rovers) my whole life. I currently have a 6.2 NA diesel, in front of a 5 speed manual Land Rover Santana box. The vehicle runs well and we use around 13L 100KM fuel (about 22 mpg). We have just bought a new caravan - 22ft and just under 3 ton. We are going to upgrade the motor and I am purchasing a 6.5ltr new engine from Peninsular Diesel. I was going to buy a 4l85e also but this means shifting my transfer case back about 8" with the adaptor available here in Australia. I have the opportunity to purchase a 6 speed Allison off a Duramax, with the adaptor I can purchase here, it means only shifting the transfer case about 4". I need to know if the Allison is the same bellhousing pattern as the Chev 6.5ltr. and will the torque converter bolt straight to the flex plate and the box bolt straight to the engine. I am ordering the engine in the next few days and NEED AN ACCURATE REPLY, I have had a couple of "it should fit" here in Australia, but nobody definite. I do not want to pay two lots of freight, so would appreciate an urgent reply if you know whether this will fit.

Thanks - Andy A (Australia)
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Old 09-30-2010, 08:53 PM
rustyk's Avatar
rustyk rustyk is offline
Captain Doom
Join Date: Sep 2006
Location: Brooker, FL
Posts: 1,192

I can't address the mating issue directly, but my 6.5L Peninsular drives a HD rebuilt 4L80E w/ Sun Coast Converters TC. To keep the RPM at best level (2,600, at the torque curve peak), I rarely get out of straight drive (3rd). My coach is slightly heavier than your rig at 8T.

You may find this thread helpful, expecially regarding gear ratios. Ed (MWrench) knows what he's talking about.

Anyway, it may be in your best interest to reconsider the 4L8xE.
'94 Barth 28' Breakaway M/H ("StaRV II") diesel pusher: Spartan chassis, aluminum birdcage construction. Peninsular/AMG 6.5L TD (230HP), 18:1, Phazer, non-wastgated turbo, hi-pop injectors, 4L80E (Sun Coast TC & rebuild, M-H Pan), Dana 80 (M-H Cover), Fluidampr, EGT, trans temp, boost gage. Honda EV-4010 gaso genset, furnace, roof air, stove, microwave/convection, 2-dr. 3-way reefer. KVH R5SL Satellite. Cruises 2, sleeps 4, carries 6, and parties 8 (parties 12 - tested).

Stand-ins are an '02 Cadillac Escalade AWD 6.0L and an '06 Toyota Sienna Limited.
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Old 10-01-2010, 09:38 AM
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Edahall Edahall is offline
Join Date: Sep 2006
Posts: 363

I found some information for you. "The Dmax, 4.3, 5.0, 5.7 and 8.1 have same bellhousing bolt pattern however, you will still need a computer to control the transmission."

Have you thought about putting in a manual such as an, SM465 (4 speed), NV4500 (5 speed). It would be quite a bit shorter and you would not have to deal with the computer controlled electronics on the Allison.

With your weight of 3 tons, it should pull well and be most fuel efficient if you gear everything so that it turns over at 1800 rpms cruising.
1990 ton 4x4 Chevy Suburban
-Cummins Diesel - 12 valve - factory rebuilt
-6 speed bullet proof manual transmission - NV5600
-Gear Vendors Overdrive
-Upgraded Holset HX-35 turbo
-NP205 iron transfer case
-3.73 gears

1982 ton Chevy Suburban
-6.2L diesel - high nickle crack free 1982 block
-Stans headers
-Ported heads
-Timing gear
-4 speed automatic
-3.08 gears
-30 mpg on freeway
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Old 10-01-2010, 11:25 AM
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More Power More Power is offline
Join Date: Feb 2000
Location: Big Sky Country
Posts: 10,205

A few things....

1- The Allison 1000, as used behind the Duramax 6600, has the very same bellhousing bolt pattern at that used by the 6.2L/6.5L diesel.

2- The Allison torque converter will bolt right up to the factory HD 6.2/6.5 (TH400/4L80-E) flexplate. (I actually bolted a TH400 up to a Duramax 6600 to perform some early dimensional checks before moving ahead with our conversion.) Also, during the early stages of the Allison 1000 development (circa 1999), GM Powertrain actually used uprated (approaching 300 hp) 6.5L diesels (and GMT-400 pickup trucks) as power sources to test the transmission. GM Powertrain engineers mentioned this to me when they brought two of their prototype Duramax/Allison equipped trucks to Montana in October 1999 for The Diesel Page & Four Wheeler mag hill test.

3- The main body of the Allison is larger than the 4L80, which could produce an interference problem with the transmission tunnel about 8-10 inches behind the bellhousing flange - unless you modify the tunnel or raise the body.

4- The Allison, being such a heavy-duty automatic, does sap a little more power from the engine than a TH400 or 4L80-E would. All automatics absorb power as it works its way through the transmission. The Allison absorbs a little more than the other transmissions we use. I'd rather consider a TH700R4 for a non-turbo 6.2/6.5 installation. The 700 is lighter, cheaper, more efficient and a better choice for a low torque application.

5- Standalone electronics packages for the Allison are available from, which would allow the Allison to be installed in all sorts of unique projects (i.e. behind a 6.2/6.5, Cummins, Powerstroke, or ?).


Last edited by More Power; 10-03-2010 at 02:18 PM. Reason: add to
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Old 10-03-2010, 05:25 AM
Sonofagun12G Sonofagun12G is offline
Join Date: Sep 2010
Location: Sunshine Coast Qld Australia
Posts: 2
Default Re Allison Box

Thanks for your replies, I have made the decision to go with the 4L85e, I can get a new one from Peninsular Diesel.I have sourced a stand alone controller, and the gearbox will fit in the transmission tunnel. I have a mate here in Australia who has a Land Rover shop, and he has given me an old auto box out of a Discovery, this has the adaptor to fit my LT230 transfer case, so all I have to do is make the other side fit the 4L85. I have found the 6.2 a bit light on towing our 3 Tonne van ( we are 6 tonne all up) I am getting about 16 mile to the gallon. I don,t have much up the sleeve though. My son-in-law has just fitted a new power project engine in his 80 series Land Cruiser. We brought a full 2010 6.5 in from Peninsular. What a rocket, it is so fast and has so much pickup, that it feels like a jet. I have just paid for my engine at Peninsular and am looking forward to getting the 6.5 TD in front of the auto box in the Land Rover.Peninsular are great to deal with. Will keep you informed.

Andy A - Australia
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