6.6 Duramax + Allison into 1990 Suburban

[The Dark Side of Will]

My Dad has a 1990 Suburban original diesel chassis.

He bought it with no engine or trans and swapped in a 500 cid Cadillac engine with fuel injection and a 4L80E trans. He also ditched the 3.73 non-floating 14 bolt for the 3.23 14 bolt full floating from his previous '79 Suburban (454/TH400) which rusted its way to the scrap heap.

Because of the overdrive and axle ratio, it turns 1750 RPM at 55 and 2250 at 80. But it has 500 cubes... it pulls it just fine, even towing.

 

The Cadillac spun a rod bearing or has a similar problem.

In adding up the cost of a built Caddy stroked to 540 with ported heads, 58x controller conversion, and eventually a 6L90E... it gets cost competitive with a Duramax really quick.

 

So a Duramax with a built 4L80E can be done, as can a 6L90E. Obviously both would require transmission tuning to live behind that engine.

 

Has anyone ever put the Allison into the 77-87 trucks? I searched that subforum and only found this one topic, which isn't exactly conclusive.

http://www.gm-trucks.com/forums/topic/153586-question-on-77-87-k2500

 

I understand that the factory Duramax trucks had a 2" body lift in order for the Allison to fit under the transmission tunnel. I @$$ume that the older trucks would be the same, but I'd like confirmation from someone who's done it or tried it.

 

My dad's truck also has an Anaheim Industries interior, which is fairly nice. It includes a large center console which would cover up any transmission tunnel surgery (and carpet surgery) which may be required.

 

Thnaks!

 

[Jay P]

Anything is possible. The mounting it is probably the easiest part. You would either need a stand alone controllers/wiring for the engine and transmission or all the wiring/ecm/tcm including the dash (and maybe the BCM) from a donor truck. I have seen a duramax/allison in a late 90s pickup and Suburban. Probably not cheap.

The duramax pickups do not have a body lift, they are the same as the gas 2500/3500 trucks.

 

It actually might be cheaper to mount the Suburban body on a Duramax pickup frame (if the wheelbase is right).

 

Jay

[The Dark Side of Will]

Of course anything's possible. I'm tying to find out if anyone has done it, if it fit without a body lift, and if not whether they went with a body lift or cut the tunnel to make it fit.

 

Everything I've read says that the diesel trucks have a body lift. That's also why GM never built Duramax/Allison Suburbans, because the "consumer" nature of the vehicle meant that the body lift by itself would not be welcomed by the customer base. GM would have to produce rocker panels and such specific to the Duramax Suburban, which would price it out of its market.

 

Anyway... neither here nor there relative to an Allison fitting in the truck.