Hi all,

New to the forum, and the world of K5 blazers since the weekend. Just picked one up. I'm not sure of the year possibly a '88, the previous owner did swap out the TBI for a carbureted crate engine. I believe the transmission is a TH350 based off of the pan shape.

The transmission shifts 1-3 well with little to no shudder or hesitation, then at about 45 MPH a grinding starts and the revs stay high indicating that it's not shifting. The transfer case is in 2H.

Also, when coming back to a stop the engine nearly dies, and to keep it running you have to give a little gas, while holding the break. In park and neutral, it idles fine.

My initial thought is that something isn't connected right because of the engine swap, but I'm no expert on transmissions.

Thanks!

 

That's because a TH350 is only a 3 speed transmission. Do you mean a 200 or 700 R4?

 

Well that would make sense, I didn't realize that the TH350 was a 3speed. Here's a picture of the pan, which was how I arrived that it was a TH350. Then what would explain the noise at 45?

Also without looking further in, there was a connection not hooked up on the drivers side of the trans. could this be what causes the engine to load up when stopped?

 

thats probably the old electrical connection for the 700r4 that came factory for that truck. should be like a square 4 wire plug. its not needed with that transmission.

also i noticed in your third picture that the vent is wide open. if this is going to be a off road truck of anykind run a rubber hose off that vent up as high as you can go. if not you should still get a vent cap for it just to keep dirt and rain water out of the trans

 

After some further digging, I found that I had the transfer case in 4L!

That would explain the lower speed, and high revs. D'OH!

abig84: Thanks for the ID of the vent line. I'll certainly be putting a line off of it with a breather!


Now i'm focused on the idle stall problem. I dropped the pan and cleaned out quite a bit of metal particles. Filled it with new fluid and the problem of the engine trying to stall in drive persisted.

I tried setting the E-brake and taking my foot off the brake (to check for any vacuum leaks on the brake system) and there was no change.

The TV cable off of the carb linkage is moving freely. I haven't adjusted it yet, right now it's retracted. From what I understand it controls the TC lockup under high engine demand. So at idle it should not be a factor, unless it's adjusted incorrectly.

Would flushing the transmission at this point be worth it?

I still have a suspicion that I may need a torque converter with a higher stall. What RPM range, I have no idea. Would I have to go a shop for advice on that?

 

The th350 does not have a lock up torque converter - 350c does and has a elect plugin on the left side of the trans - what you call a tv cable on a th350 would be the passing gear control that drops the trans from 3rd to 2nd when passing ect - you also should have a vaccume modulator on the rear of the trans if yours is a th350 and if it's not hooked to vacumme it could cause stalling and shifting problems - hook it up too full vacuume at the intake manifold or the base of the carberator - if you have the modulator hooked to vacuume and after adjusting the passing shift cable I would do a good tune up and carberator adjustment, good possability your power range at idle is too low