Hi folks,

i did my due diligence and searched around, but didn't see any posts like this. I have a G30 van w 140k miles that has been slipping occasionally for awhile, but just got really bad all of a sudden on a trip to NYC; slipping in 3rd and 4th, and undriveble when hot. When the tranny cooled off, i could get down the road a bit more until it started slipping again. I put some lucas in and that seemed to do the trick, and i was able to get home. Right now, after the lucas, it seems to be doing fine. I was going to open it up and check and change the filter and fluid, but was advised against it by some local hillbillys that i trust that said changing it will do more harm than good.

what is the easiest way to tell if it is on really on it's way out? (in which case i will just change it out for a junk yard tranny)

thanks!

here are my FAq answers:

1. Fluid level okay while running, warm, level surface. yep
1a. Fluid color and smell. not bad, just a tad brown
2. Speedometer reading correctly. yep
3. Shifting normal/hard. normal, smooth shifts
4. Shifting into OD okay? yep (although i am starting to be a bit unsure of this on this last trip)
5. Any service engine light: yes service engine soon which went off after i unplugged and replugged the TCU
6. If SES light on, what codes do you have? haven't checked. no machine
7. Model year: 94
8. Describe symptoms: slipping when hot
9. Does the engine come up to full temperature? yup
10. Any service work recently done that may contribute to your issues. nope
11. Does the TCC lock up (or how many "shifts" do you hear?) not sure what this is. but does shift thru all gears.
12. Are you experiencing any kind of slipping? yep
13. What type of rear do you have? (Check RPO codes) 4.10/ 3.73/ 3.42 or 3.08 jees, i dunno
14. If you have an accurate tachometer, what is the RPM at 55 or 65 no tach

If it was a 4L80-E your transmission would not let you slip. You would have defaulted into 2nd gear.

thanks,

you know i just assumed i had a 4L80 because the van is a 1 ton with a 6.5l, but is it possible that i have a 4L60? I looked all over underneath and couldn't find a tag, though i did write down a couple of casting #'s: the main body casting 8684198..3 and another 8677464 (then a little circle with AF inside) then L1 also a tag that i think had 94 4070 but it was hard to read

i'm pretty sure, judging from the pictures, it's a 4L80. it has a 17 bolt pan. etc

If it is a 17 bolt transmission it should be a 4L80-E. Look for a input speed sensor towards the front.

Third and 4th gear slipping? Transmission getting too hot? Drop the inspection cover and have a look see at the torque converter for discoloration.
Hook up or get the transmission to a shop for a pressure gauge. Readings should be ~90-115 PSI in the forward gears. Up to 310 or so in reverse.
That being said the slippage could be OD in the torque converter.