07 Tahoe trans fluid change.

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653
Location
GA
Thread starter
My Girlfriends 07 Tahoe Z71 was neglected service wise in the earlier parts of its life. Of course she has no idea if the transmission has ever been touched. Has 195k but runs reasonably well. Trans fluid is dark and smells well used but not necessarily burnt. I decided to suck 3 quarts out of the dipstick hole and replace with some Supertech dex 6. Still feels normal so far. Rear end assembly was replaced before 100k. No known services with that either. Sucked that fluid out and threw some Valvoline Full Syn 75w90 in it. Was debating 75w140. What are your thoughts on going thicker?
 
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1,906
Location
Seattle-ish, WA
Take some more out or better yet pump it out the cooler lines; 3 qts is not yet enough to replace all that spent fluid. The 4L60e will run "reasonably well" right up until it fails. Treat it right and help it last to it's full potential, it's a good (great?) transmission if not neglected like most are. More than slightly embarrassing GM was still stuffing 4 speeds into flagship trucks in 2007, but that's a different rant. wink Unless you are going to tow a lot, do 80w-90 in the diff. No need for arctic-capable 75w in Georgia, why dilute the lube with additives you don't need? If you are going to tow a lot, then 85w-140. The winter rating on gear oils is parallel to engine oils. If you live in a warmer climate, don't buy adulterated lubes designed for cold climates. If you just put in syn 75w-90, then run that 40k and check it. Then put in a more appropriate grade then, or when it needs it.
 
Messages
653
Location
GA
Thread starter
I was hesitant to change too much fluid because I don't want it failing like some neglected transmissions do when they are introduced to new fluid. I will probably extract another 3 quarts next oil change. 75w90 is the factory weight for the diff. Since these rear ends aren't known for being the most stout I was thinking of 140. The most it tows is a Jetski occasionally.
 
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6,710
Location
SE British Columbia, Canada
Slipping fluid on a regular basis is really not that bad if you keep it up on a regular basis. I do the same, but I also get the transmission pan pulled every five years anyway and they change the filter. As for the rear end, I believe it has a magnet below the gear set that builds up with metal. It's good to clean that out. I have done it every 5 years on my 14 bolt 3/4 ton and it now has 200,000 miles with no repairs required. Ford liked to spec 75w140. Chevy pretty much stayed with 75w90. If I lived in Texas and was towing I suppose I'd use 75w140. smile
 
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4,785
Location
VA
Originally Posted by Anthony
I was hesitant to change too much fluid because I don't want it failing like some neglected transmissions do when they are introduced to new fluid. I will probably extract another 3 quarts next oil change. 75w90 is the factory weight for the diff. Since these rear ends aren't known for being the most stout I was thinking of 140. The most it tows is a Jetski occasionally.
Great plan on the tranny fluid exchange. Well, at least I agree. I don't know if I'd go to 140. I'd fill better going with a 110. I'll PM you some info.
 
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