2001 Blazer, 4X4, 4.3 -
Tranny fluid got into vacuum lines and blew the actuator (2x). Obvious transfer case input seal problem. I didn't have the $$ to have it fixed so I just blew the lines out with compressed air. This would help for a day or so. The truck then began running very poorly. It idled fine, but when the engine warmed up, there was serious spark knock under load and could not achieve more the 45 mph.

I brought it to a tranny shop to replace the seal and was told the tranny was going bad - brass on top of the tranny filter. Tranny shop gave me estimate between 2,500 and 3,000 to rebuild the tranny. I choose to replace the tranny myself. I picked up a used tranny (w/100k miles) for $500 and swapped it last weekend. I replaced the transfer case input seal while I had it out.

Now with different trans and new input seal, I'm still having the exact same problems. Once it warms up it doesn't shift right and spark knocks terribly under load.

Any ideas would be greatly appreciated.

 

Have you done a tune up? Checked compression? Any codes?

A transmission will not cause spark knock. And if it is getting detonation, it should have stored a code.

 

There were prior to swapping the tranny. Each time that I blew out the vacuum lines, the codes would be removed and the check engine light would no longer be on since I had to remove the battery for greater than 15 min. I went to AZ and they said there was a number of codes, one of which was mass air flow. They removed the codes and I don't know what any of the others were. I've put about 30 miles on it since the swap and there are no codes right now.

I'm going to check the plugs and also re-check the transfer case level right now. Also I'll check all the vacuum lines.

Truck also has the "stuck in vent mode" issue. I took the controller out and did what I could to blow out the vacuum supply line. There is a hissing from the ac/heat control unit although this symptom was present long ago.

Could the presence of tranny fluid in the vacuum lines have contaminated any of the sensors? Is there a better way clean out the vacuum lines?

Thanks.

 

If there was a decent amount that would make it to the engine, it is possible. But like I said, you really need those codes. Codes should never just be erased and ignored. They were stored for a reason.

 

At the time, there was plenty of tranny fluid that came out of the vacuum lines.

Yeah, the codes sure would be nice right now. I had no idea the AZ guy was going to erase them. Shouldn't the current poor performance throw a code?

Please let me know if you have and other ideas? Thanks.

 

Turns out I had two problems happening at the same time. I thought the tranny fluid in my vacuum lines was what was affecting the performance but it turns out the catalytic convertor was plugged.

I have taken care of this and now my blazer is running better than ever. Thanks for your input and maintaining this forum!

 

So do you think the original Transmission you had in it was bad or was the Shop just pullin your Leg ? I no you fixed the problems on the Cat. Thats good, you goter done.

 

I know the input seal on the t-case was bad - this is why my tcase overfilled and allowed tranny fluid into the vacuum system, and the reason I brought it into the shop to begin with. The tranny was getting a little tired but do not believe it was bad. There was some brass on the top of the filter as the shop told me (a sure sign of wear) but when I got home I could tell that they never opened the trans pan to confirm this.

In retrospect, I wish I would have pulled the tcase myself at the time I diagnosed it (with the help of this forum) and repaired the seal myself. This would have saved me a whole lot of time and trouble and was not that difficult to do. The most difficult part was getting it back in as the tcase is awkward to balance on a floor jack. It would have been MUCH easier with 2 people.

When replacing the seal, I did notice a little end play on the input shaft of the tcase - maybe 1/16". I'm hoping this is normal. I will continue to check the tcase level religously.

Signs of a plugged Catalytic convertor:
- car warms up very quickly (within 1 mile of driving). The exhaust cannot pass through the system so the heat builds up quickly.
- car runs a little warmer than normal
- the transmission Bucks
- very limited RPM's
- Sounds like there is an exhaust leak near the manifold. The exhaust can't get past the convertor and needs to go somewhere.

 

how is the plugged cat associated with the trans bucking?? I have similer issues and horrible gas mileage but never smell eggs or hear any thing rattling around in the cat?

 

To answer your first question, they aren't. But a clogged or restricted cat can cause a misfire that would make it seem like a transmission issue. One way to diagnose a catalytic converter problem is to remove an upstream sensor and drive the vehicle. If it drives normally, then the catalytic converter is restricted.