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Engine and transmission issues 99 Suburban

Haven't had an issue since replacing the FSD. I decided to mount it just behind the grill on the passenger side. It should get plenty of air there to keep cool.

IMAG0156.jpg
 
had to open my mouth...

same issue arose again today. driving long distance, mostly back roads with lots of acceleration up hills and such, and by the time i made it to the interstate, 4th gear dropped out again and didn't come back until I had been parked for a couple hours. the 1st to 2nd shift was also very hard during the time that 4th gear was non-existent. still no SES light or codes that didn't trigger the SES. drove home a few hours later and 4th gear worked flawlessly. temps didn't get above 40 all day.
 
Try changing out your Oil Pressure Switch (OPS)......From my experience when the OPS is bad or unplugged you loose overdrive along with a few other problems.

Again just a WAG***

Or you can check it, there is a reference chart in the Tech library for temp and what the ohm readings should be.
 
juddspaintballs said:
I'll check that out.

I'm wondering if this is related to transmission temps. This usually happens on long drives...and mostly under either tow or uphill conditions.
Click to expand...

Heavy transmission load with temperature from long drives.
The 4L80E needs fluid changes every 25K. The TCC valve body wears out otherwise and can slip the TCC. This will "Limp" the trans.

Likely you have a TCC valve issue or slipping in the TCC clutch or OD gear when hot and loaded. Aka rebuild time.

Limp is loss of 4th, OD, and hard shifting. You should have a code. Possible defective computer not storing codes.

Check the trans connector for oil leaking out and clean as necessary. The cure is expensive for a leak.

have you pulled the trans and oil coolers away from the condenser and cleaned behind them?
 
I haven't cleaned behind the trans and oil coolers and cleaned behind them. I'll also check the trans connector for leaking. Haven't noticed anything yet.

There is no code still. The computer still stores the code for the boost issue I had before I built my own turbo-master.

I know these are different transmissions, but when the TCC was slipping and not locking like it should in my Blazer's 4L60E, it felt completely different than this.
 
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