8L90 Automatic
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Teching In
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From: Rockford, Mich
8L90 Automatic Here I am drooling over the 2016 GM 8 speed and Peter MJ Posted on the internet; 29th January 2014; a scathing report saying the GM has coveered up a seriously flawed design. Is he coming from a racing application or everyday use. I wish to put the 8L90 in my 96 Roadmaster thinking it would give me better acceleration as well as better mileage. My car will be an exciting grocery getter. Am I biting off more than I want to chew?
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From: Ann Arbor, MI
Connecting a 8L80 would be very complex as its built-in TCU requires a CANBUS connection to a compatible ECU and perhaps BCM. There are no current aftermarket controllers and there may never be any.
Your best bet would be a 4L80E, or if you really want more gears, a 6-speed version of the 4L80E as sold by TCI and a few others.
Your best bet would be a 4L80E, or if you really want more gears, a 6-speed version of the 4L80E as sold by TCI and a few others.
Last edited by mrvedit; Oct 7, 2015 at 09:37 AM. Reason: Typo
Teching In
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8l90 The 8l90 has an external TCM, unlike the previous 6 speed auto varieties. I must assume that Powertrain Control Solutions will likely be first with a standalone TCM. But time is always the issue. I have settled for the 6L90 behind my 6.0L, in an old school bus which should weigh in at around 13,800lb.
With the stock 5.83 rear and 37 inch tyres, it should hold 6th gear at 60mph on the hiway just fine at 2090 rpm. If it drops a gear it will spike up to 2670 rpm. I would be happier if somebody out there has a remedy for getting the Tow/Haul to work with a standalone setup with the e38 pcm.
Which is to say, I dont have a bcm currently. On a steep downgrade i gotta be able to stop the thing! NO lol.
With the stock 5.83 rear and 37 inch tyres, it should hold 6th gear at 60mph on the hiway just fine at 2090 rpm. If it drops a gear it will spike up to 2670 rpm. I would be happier if somebody out there has a remedy for getting the Tow/Haul to work with a standalone setup with the e38 pcm.
Which is to say, I dont have a bcm currently. On a steep downgrade i gotta be able to stop the thing! NO lol.
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http://gmauthority.com/blog/gm/gm-transmissions/m5u/
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HEAVY Duty GM were essentially keen to reduce the 8L90's material weights and also ditched the center support for a splined case; And external TCM.
My 4x4 6L90 came with converter, full of oil: ready to go; And weighed in at around 109kg. So GM have done real well with the 8L90 diet program.
When I pulled the 6L90 down to convert to the Cadillac CTSV Output Shaft, it was a real no-brainer to dummy the empty bell, case and tail-housing back into the frame for a drive-shaft cut. And still I say, don't drop that on your toes while wearing your flip-flops in the garage.
My 4x4 6L90 came with converter, full of oil: ready to go; And weighed in at around 109kg. So GM have done real well with the 8L90 diet program.
When I pulled the 6L90 down to convert to the Cadillac CTSV Output Shaft, it was a real no-brainer to dummy the empty bell, case and tail-housing back into the frame for a drive-shaft cut. And still I say, don't drop that on your toes while wearing your flip-flops in the garage.
On The Tree
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The 8l90 has an external TCM, unlike the previous 6 speed auto varieties. I must assume that Powertrain Control Solutions will likely be first with a standalone TCM. But time is always the issue. I have settled for the 6L90 behind my 6.0L, in an old school bus which should weigh in at around 13,800lb.
With the stock 5.83 rear and 37 inch tyres, it should hold 6th gear at 60mph on the hiway just fine at 2090 rpm. If it drops a gear it will spike up to 2670 rpm. I would be happier if somebody out there has a remedy for getting the Tow/Haul to work with a standalone setup with the e38 pcm.
Which is to say, I dont have a bcm currently. On a steep downgrade i gotta be able to stop the thing! NO lol.
With the stock 5.83 rear and 37 inch tyres, it should hold 6th gear at 60mph on the hiway just fine at 2090 rpm. If it drops a gear it will spike up to 2670 rpm. I would be happier if somebody out there has a remedy for getting the Tow/Haul to work with a standalone setup with the e38 pcm.
Which is to say, I dont have a bcm currently. On a steep downgrade i gotta be able to stop the thing! NO lol.
Last edited by zgp; Dec 6, 2015 at 12:25 AM.