Boost drop from 15-12lbs changing trans fluid?
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Boost drop from 15-12lbs changing trans fluid? Last week I ran my car at the drag strip and it was really loose. The only change I made this week was the trans fluid. I went from Tractor 303 fluid to type F. The car seems to have tightened up. I would have thought it wouldn't have. With the 303 fluid the car wanted to "sliiiiiide" into gear like it was a manual trans and I was slipping the clutch. I went ahead and drained the pan only and put some new Type F in it. Didn't completely pull the trans and convertor, just pulled the pan and let drain for a while. Ended up putting 6 qts back in.
The car drives and sounds the same but just doesn't hit 15lbs of boost. It now only hits 11-12lbs. Would just changing the fluid do this or is something else going on. Both turbo's are spinning, I have the same heat on the exhaust on both sides, plugs look good, car sounds and runs good. Just doesn't hit 15lbs. I have a manual boost controller that is all the way off so I can just turn up the boost controller but just wanted to make sure that a wastegate hasn't failed or something. I have a wastegate on each side and both are getting hot, just like normal. They turn into the atmosphere, not the down pipe.
Not that it would matter but I also changed engine oil from Mobile 1 full synthetic 10W 30 to Valvoline VR1 Racing Oil 20W 50
Thanks.
The car drives and sounds the same but just doesn't hit 15lbs of boost. It now only hits 11-12lbs. Would just changing the fluid do this or is something else going on. Both turbo's are spinning, I have the same heat on the exhaust on both sides, plugs look good, car sounds and runs good. Just doesn't hit 15lbs. I have a manual boost controller that is all the way off so I can just turn up the boost controller but just wanted to make sure that a wastegate hasn't failed or something. I have a wastegate on each side and both are getting hot, just like normal. They turn into the atmosphere, not the down pipe.
Not that it would matter but I also changed engine oil from Mobile 1 full synthetic 10W 30 to Valvoline VR1 Racing Oil 20W 50
Thanks.
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I probably shouldn't have. I put 1500 miles on it in the last month and a half. When it gets hot after a couple hours of driving I could hear the drive train a little when I opened the hood. I figured the heavier weight oil wouldn't hurt since it was hot out. Now I am thinking I should just change it back. The problem is that I don't know if it is because of the trans fluid change or the engine oil change. The 20w/50 maybe way too thick. If it is I will change it again in the morning before I take it to test and tune. I guess the 5.3 are just a little noisy and I am not used to it. The oil looked perfect when I drained it. Maybe I read too much into the valve train noisy.
Thread Starter
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Thinner trans fluid, higher stall speed, less load on engine = less boost...
Combine that with the increased drag placed on the turbo shaft due to the unnecessarily heavy oil weight, and I could see the 3lb drop...
Combine that with the increased drag placed on the turbo shaft due to the unnecessarily heavy oil weight, and I could see the 3lb drop...
