Thread: Help me diagnose my Turbo 350

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I posted this in another forum, but I will post it here because I want as many responses as I can get as quickly as I can.

I had to leave it at my friends house and will have to tow it to school tomorrow. I just thought I would question the expert panel as to why you think it failed. The story goes, I was leaving my friends house and everything was fine. I drove about a mile and was going to go to the store. I couldn't find a parking spot and put it in reverse and it wasn't there. I put it in drive and it was there but weak. After several tries, I managed to get a weak reverse that was hardly enough to get me back on to the road. The transmission was slipping badly. I went to drive and there was nothing there. I went all of the way down to the first detent at got a weak first that slipped badly and was able to limp the mile back to my friends house. I tried to shift to second, but it was non existant. In the dark, the fluid appeared black and was definately burnt. The fluid was fine not long ago and the transmission gave no warning of this failure. No prior slipping and no odd noises.

How many miles are on it?

Your pump has dropped pressure probably due to a blocked filter, so with low pressure to the clutch packs, it has caused them to slip and burn.

I would say pull your pan (after draining the fluid of corse) check your filter.

2 choices from here if the filter is blocked,replace filter new fluid nurse it along. Or the proper way, pull the whole trans and rebuild it.

I will probably rebuild it. I'm looking at this kit, it seems the most complete with bushings and everything http://store.summitracing.com/partde...3&autoview=sku

Yup, that s the way, that is quite a kit. I would also recommend that you look at your bands as well and see if they are burnt. Remember to soak your new clutches in tranny fluid overnight so that they go into the box wet. Also a dab of rubber grease on the clutch pack seals helps as well. Have fun . S

I didn't realize that one didn't come with bands. Maybe I'll have to get this one: http://store.summitracing.com/partde...3&autoview=sku

All of this is kind of exceeding my current budget of $20.15. Hopefully my school will get my paycheck to me soon so I can do this.

A more in budget kit would be something from ATP, but I don't see any kits that come with bands or bushings. I like the idea of having a complete kit so I can bring the transmission back into spec. I have acess to all of the measurement tools necessary to do this.

I haven't heard anything really good about B&M. TCI seems ok, but their kits aren't much cheaper than the Hughe's stuff and the Hughe's is much better quality.

I will throw on the $88 Summit 1500-1900 stall torque conveter. All of this is going into a truck with a 350 making big block torque and may see occasional towing use.

If you are using the vehicle for towing the smart money would be to invest in a seperate trans oil cooler that bolts onto the front of your radiator, this keeps the fluid cooler, thus extending fluid and tranny lifespan.

if you wanna make her limp a little longer before you can rebuild and it is your filter thats clogged, then your clutches are probably on their way out.. new fluid will just make them go even quicker, try re-using the old fluid after filtering it out, tranny fluid is very corrosive, and the fresher it is the stronger... its an old trick to keep a dying tranny going, also, your bands might need some adjustment.... could also be vaccum failure causing it not to hold a gear... not neccisarily, but its possible.. really she needs a rebuild though

Oh, it's definately time for a rebuild. At least one of the frictions or bands has disintegrated. I got the truck back to school today. I haven't dropped the pan out but when I pulled the dipstick it is black with clutch material. The odd thing is, the fluid ISN'T burnt like I thought it was.

Sounds like one of your piston orings seals went out, as others have said get a rebuild.

Update: The loss of gears was caused by a plugged filter, however, the debris did not come from the clutches. It was the front planetary.

Hey 76,

I did a rebuild on the Th350 in the s-10 a little while back. Looks like you need to hunt out a planet set. I found a performance rebuild kit from Alto on ebay that included the red clutches and the steels ( extra clutches and steels if needed) the kevlar band plus all the seals and complete bushing set for @ $75.00 plus shipping. This was a first time experience for me as well. The only tough parts were pressing the pistons out of the drums without bending the retainers and the pump alignment. I took the pump to a retutable tranny shop and had them set the new gears and align everything so I could just drop it in. Be careful of the seals on the pistons that they dont get kinked up( like the other post says, use patrolium jelly or some thing else that will disipate with the heat of the trans). If you dont have a manual, try this link:


http://th350.netfirms.com/browser.htm

If you have never attempted an auto rebuild, I strongly recommend you study this manual first. Take your time and good luck.


This is the GM manual on the THM350 and it goes into detail for a complete overhaul.

Darn, should have checked ebay. I bought the Hughes kit off Summit and that was $270 and it uses red alto clutches, kolene steels, and had bushings. I did buy a replacement planetary off EBay. It was a little pricey and the total came to $60 including shipping. The front planetary came with all of the other internals that I will use as spares. I may start assembly tonight, I can do the low/reverse piston tonight as soon as I finish the case. Once I get everything else, I can assemble the transmission and order a torque converter. I am looking at the Hughes Tow Master converter with an 1800-1900 rpm stall, but the best price I have seen is $160 and that is a little high. I didn't need new pump gears or anything else, that was all in excellent condition (the filter really did its job).

I used this convertor for my application. Looks like they have went up a little. No complaints so far.http://store.summitracing.com/partde...3&autoview=sku

Originally posted by s10streeter
If you dont have a manual, try this link:


http://th350.netfirms.com/browser.htm


This is the GM manual on the THM350 and it goes into detail for a complete overhaul.

I got all excited about the GM TH-350 manual until my server blocked the link siting "General Pornography" as the reason. I'm a teacher and the school's server is quite picky on what it lets though. I'm sure it's not, but for some reason it's labeled that way. Can someone send the manual in an email...Copy the info into Word and email it to me or something? (jcanaday@elkhartisd.org)

I'm keeping an eye on this thread...I may be rebuilding a TH-350 myself soon...