More Suburban Tranny help?

[R/T]

Ok, the 1990 Suburban shifts in and out of OD while driving down the road. I know there are a number of things to look at, the question is, where to start?

[Biggerhammer]

Check the vacumn lines to the modulator. They could be cracked or loose. Have you been under the hood for anything lately? Maybe something was knocked loose. When was the last fluid/filter change?

[catfishblues]

Is it kicking in and out of OD, or is the TC locking and unlocking more frequently than before? Have you goine up in tire size lately? Does the engine feel weaker than it used to?

[rockrat]

If it is a 4L60 E Could be lots of things unfortently usually expensive. if 700r4 check the detent cable and make shire it is adjusted corretly.. Lock up is done electronicly Based on TPS. I have had numerous issues with the TC on the 85-88 model yr. You can also uplug the connection on the dr side top of the pan area and drive it to diagnois more ( does it do aything differnt etc)

[R/T]

I'll work to get a little better info this week. It's been a while since it was driven, but now I've got some ideas where to start looking!
Thanks, as always guys!

[ZukiJon]

Change the fluid. 

[dadstoybox]

1990 should be 700 r4 and likes nice clean fluid and filter. also as scott said check the detent cable,they can back off. our 93 is the same and other than normal maint. has needed nothing and she's got over 250k on her.