GM 8-speed


Living in the Past
Supporting Member
Jul 19, 2009
Mid-life crisis
After driving a used 1963 Nova, my father owned new Chevrolets from 1971 to 1984. The first one lasted to 1975. Transmission was starting to shift badly, and the dealer told him a ‘bearing failed and sent bits down the driveshaft that damaged the differential.’ My Dad was a teacher and bought the story. Traded it in on a 1976. Four years later, rust cancers started popping all over the body. Not just along the rockers. The dealer blamed poor steel in the 1976 model year. He traded it in on a 1980.
In 1984, a couple cam lobes went flat and he paid $800 to replace it. His high school kid asked him, ‘have you ever looked at Honda?’ He downsized to a 1984 Accord manual. He switched careers and got into sales. He put 200,000 miles on that car, and in 1989, replaced it with a new Accord, and put about the same on it. He’s owned five other Hondas since then.
Anecdotally, the ‘caster’s story holds true. And, I will point out, the design includes the parts, assembly and finish. So thanks for confirming that the 200-4R or TKO 600 is still the right answer, even if I decide to go with an LS3. Eventually. Maybe.


Royal Smart Person
Feb 7, 2019
I love our beloved G body GM's, but I would NEVER purchase a new GM, FORD or CHRYSLER product, the quality control isn't there, along with the poor designs that are rushed out the door, the industry is moving at a pace that manufactures just cant cost effectively keep up, or perfect design issues for that matter, and ultimately the consumer is left holding the bag, or a handful of repair receipts that are not covered under the manufactures frivolous warranties, just unbelievable. I hope people vote with their hard earned monies and buy Honda, Toyota, and some other HIGHER quality vehicles that actually WANT to see you coming back to the dealer for your next purchase! What GM, Ford and Chrysler are doing, is nothing more than criminal and nothing shy of inexcusable!


Thread starter
Apr 25, 2009
I won't be any more specific then to say he makes some valid points. Just wanted to post it up in case any of you guys might be covered. Also, these transmissions will be bolted to lots of LSs that may be swap candidates in the future.


Supporting Member
Apr 3, 2015
Spring, Texas
My boss's last company truck was a 17 Sierra with that that transmission. He traded it early over lack of confidence in the trans. He likes his 20 which has the 10 speed, I guess.


Comic Book Super Hero
Feb 16, 2009
Western MN
The root problem is computer science majors who have no idea the limitation of mechanical systems designing control systems that control mechanical systems. I'm not saying they are bad engineers, just that there is too much to learn to understand a coding language/controls philosophy AND understand manufacturing tolerances and quality control AND understand mechanical design math stuff. It's tough to find someone that knows one of of those things let alone two or all three.

In theory you can command a 0.0001 second shift time. In theory you can command line pressure to rise from 120 to 250 PSI in 0.0001 seconds.

But, inertia, losses, compliance and tolerances are a Be-yotch.

It's easy for the controls engineering group to say 'not my problem, it's the mechanical group's problem' and the mechanical group to say 'it's clearly a controls problem' and nothing gets solved. In my experience the mechanical design group ends up diagnosing and either fixing it with a mechanical part OR tells the controls group what they need to do. Problem is the mechanical group is trying to figure out the gears, clutches, housings, and sensor placement so they are stretched thin.

The fact that the problem is on 8l45 and 8l90's says it's a controls problem since they copied and pasted the solution (and problem) from one to another.

Having design flaws isn't just a GM problem, but it is a GM problem that they won't fix it. Because short term profits because shareholders yo!


Royal Smart Person
Supporting Member
Nov 17, 2018
West Virginia
New car quality control sucks? GTFOH. You can't be serious. Where were you from '75 to '95? Twenty years of glued together, slow as a bloodhound, rolling crap.

My wife's 2017 RAM with 5.7 and 8-speed and loaded with options, I wouldn't trade for anything. It ain't missing anything and only costs tires, oil changes every 10,000 miles, and insurance. My 2007 Magnum SRT8 has 120,000 miles on it, 70,000 of which had a 0.630" lift cam and 461rwhp at 20mpg+. Oil changes at 10,000 miles and the only trans fluid change happened at 40,000 when it installed the ProTorque converter.

Let's face it, GM just sucks anymore. The trucks have been *ss ugly since about '87, and the cars haven't been much since about '72. Everything sucked in the late '70s, '80s, and '90s, so GM looked like a boss at the time. The Grand National was the exception, and that's even hard to remember since today's cars are so much better all around. After 2000 some of the GM cars were excellent looking and performing, WS6, G8, GTO, CTS-V, Corvette...................................

Hey, you brought it up............:p


G-Body Guru
Sep 1, 2018
Southern New Jersey near Philly
I forgot to add that GM's late model transmissions all (6 speed and 8 speed) seem to be ZF based; case layout of cooler lines at front left, case connector at right rear and gear train. All ZF. They do not have ZF markings or numbers on them that I have seen. The new 10 speeds are ZF and have the numbering on the outside in the common font used by the German's.
Now Ford, started using ZF automatic transmissions in 2006 on the V8 Explorers, Mountaineers, Aviators and the Expedition and Navigators. They call theirs a 6R80. If you had hands on it, it is a ZF 6HP26 as used in many BMW's, Jaguars and Land Rovers. Ford engineers made changes such as removing a lot of the bearings in between clutch housings and using bushings. They also use a conventional steel pan. They have also come out with a 6R140 which looks like a super sized version of the 6R80 for use in the heavy trucks behind the diesels.
Using the ZF based transmissions was the best thing Ford ever did as far as transmissions. Their failure rate is very low and they can handle a ton of power (I have a friend with a 2017 5.0 Mustang putting 800 horse power through one). The new Ford 10 speed is the same ZF unit that GM is using with their own tweaks. It too can handle a ton of power.
Last is Chrysler with the 8HP ZF transmissions that they are using in most of their rear drive applications. The only issues I have seen with them are electronics/valve body issues. Chrysler will not do anything above a valve body replacement on them at the dealer level.
Their failure rate is relatively low including when put behind the 700 horse power Hell Cats.
One thing I will say about ALL of the ZF based transmissions is that you never see hard parts failures like you used to see with the GM, Ford and Chrysler design/built transmissions.
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