NEED HELP 6l90e Rebuild Suggestions

rmarles

Original poster
Member
Jan 31, 2016
4
London, Canada
Hi all

Took the truck to one of those local "quick oil change" shops before Christmas and they asked if I wanted to do a tranny flush. It has ~143k miles on it, so it was on my to-do list, but thought "when am I going to have time"? So I went ahead and let them do it - worst idea I ever had. Went from being very responsive to all kinds of issues, slipping, overrev between the 2-3 and 3-4 shifts, etc. It drives "ok" but not like before. The shop has done top ups, additives, etc but is pretty much walking away from me on this. (That's not really the point of this thread however.)

Looking at taking the truck to a local shop and potentially getting the transmission rebuilt. Figured if I'm gonna have them do it, I should look at what upgrades I should have completed while it's all apart.

Not knowing much about automatic transmissions (I've only ever really had manual transmissions), looking for some 'must do' suggestions before I proceed. I admit I'm just getting started on the research so there may be a good post on this I haven't come across yet.

It's a 2011 Suburban 2500 LS with the 6l90e.

Thanks in advance!
 

felicie

Member
Jan 13, 2013
171
You might want to check out a company called www.monstertransmission.com They sell upgrade kits, all you have to do is decide how far you want to go.
 

mrrsm

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Oct 22, 2015
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Send a PM to @Sparky ... He has the Chops in the Knowledge Department about the GM Transmissions and will steer you right...
 

Sparky

Member
Dec 4, 2011
12,927
Unfortunately I don't know anything about that transmission. I'm not a trans guru, I just know enough about one particular one (the 4L60E, since I've had 3 of them) and its valve body weaknesses/upgrades to be dangerous! :tongue:

That being said, do you know what kind of flush they did? If they did a reverse flush... :duh: I HATE shops that do that. They should know that can cause trouble as it knocks the stuff off the filter and shoves it in reverse into the guts of the trans! Did they change the filter when done or no?

The only flush that should ever be done on a transmission is forward pumping the old fluid out entirely, replace filter, new fluid in. That's it. This pretty much goes for any transmission.

Before you rebuild your transmission though, if they did a reverse machine flush it may be worth doing a forward flush (the right way) and new fluid and filter again. It may not have killed it, just clogged it with crap.
 
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mrrsm

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Who was I thinking of...?
 

rmarles

Original poster
Member
Jan 31, 2016
4
London, Canada
You might want to check out a company called www.monstertransmission.com They sell upgrade kits, all you have to do is decide how far you want to go.

I checked them out - they don't specifically have 6L90E on their site but I'll give them a call (the 6L80E is likely a very similar beast). Good reads so far!

That being said, do you know what kind of flush they did? If they did a reverse flush... :duh: I HATE shops that do that. They should know that can cause trouble as it knocks the stuff off the filter and shoves it in reverse into the guts of the trans! Did they change the filter when done or no?.

Thanks for the reply - they unhooked the cooler lines and let the transmission pump out the old and draw in the new using some sort of a reservoir designed for that. The filter wasn't swapped, there's no line on the invoice for it.
 

Sparky

Member
Dec 4, 2011
12,927
OK, at least they didn't do a reverse. That's good.

I'd start with a pan drop and change of filter though. That filter needs to be replaced, if it is clogging up it could cause all sorts of trouble due to lack of proper fluid pressure. And I'd make sure that the fluid used is Dexron VI.
 
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Gary P

Member
Apr 18, 2016
13
Upstate NY
I've heard of some horror stories from having a reverse flush done on an "older" transmission. It may be OK on a newer one, but when it's old, and especially if you don't know it's maintenance history, I would just drop the pan, change out the filter, and add fluid.
 

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