Turbo 350 Disassembly

[HotRodPC]

Also, remove the 3 pressure tap plugs. This is not always necessary, but a good idea so that you can run some air thru the tap ports in the event some debris has been trapped in the ports. These ports are only used for transmssion testing and diagnotics.

This is what the pressure tap plugs look like out of the case.

Here is what this side of the case looks like with pressure taps and accumulator removed. This case is now 100% stripped and ready for cleaning and rebuilding at this point.

 

[Swims350]

hey hrpc, what does one use to block movement of that 1-2 piston once removed? I heard over and over to block it's movement when you remove the spring.

Also I hear alot of the time you can get the codes off the cover to tell you more info on the trans, kind of like an engine suffix, but then again I hear most shops have buckets of them and just throw on whatever and don't keep them matching the original trans.

That hole for the pick, that's where my case is broke, it goes up about 3/4 inch above the hole with a crack and barely hanging on, then the lower section including the hole is just gone. I can't beleive the SOB built it for us and didn't do anything with it, like change cases or something.

 

[89Suburban]

@ swims - That sucks!

@ HRPC - Great pics and step by steps!

 

[HotRodPC]

hey hrpc, what does one use to block movement of that 1-2 piston once removed? I heard over and over to block it's movement when you remove the spring.

Also I hear alot of the time you can get the codes off the cover to tell you more info on the trans, kind of like an engine suffix, but then again I hear most shops have buckets of them and just throw on whatever and don't keep them matching the original trans.

That hole for the pick, that's where my case is broke, it goes up about 3/4 inch above the hole with a crack and barely hanging on, then the lower section including the hole is just gone. I can't beleive the SOB built it for us and didn't do anything with it, like change cases or something.

On the 350 I don't know that you need to block the accumulator piston from moving. Some models because the accumulator is actually in the pan near or under valvebody. In those cases some special tools are used to hold it in place, sometimes there is a C clip that hold it onto a pin etc, just different varietes of accumulators. This 1-2 accumulator isn't one of those.

Also yes, SOME year models have #'s stamped on the acc cover, some other trans models have #'s stamped on the acc cover. This paticular trans does not.

That sucks he built yours that way. That's the difference in builders pride in their work. I am using a differant case for this build. The ears on the bell housing of this trans had been cut off. Sometimes necessary if you are putting a trans in tight quarters like Tbucket build for example. But this is in an El Camino with headers so someone may have cut it off to be able to install the trans without removing the headers which was stupid. It weakens the bell housing. One side they got real close to a bolt hole and it appears to me it has a light fracture or could easily fracture and break. So, I told my bro I wouldn't build his trans. Being the good guy I am, I ended up donating him a donor trans core which is why this disassembly didn't have the pan or good detenct cable on it. The case is rock solid though. So are the hard parts other than the broken drum and input shaft. I only spent $20 on the core and I knew it had a $40 shift improver kit, so I'm keeping than for later build of my own. Its drilled for Stage 1 RV/Heavy Duty.

 

[Swims350]

what part did they cut off I didn't even notice.

 

[HotRodPC]

what part did they cut off I didn't even notice.

I missed this post swims. They had trimmed the flanges on both sides of the bellhousing. Sometimes common to make a trans fit in a smaller 4 cylinder car that has been V8'ed or many times in like kit cars or T bucket projects where space is very limited. It does weaken the structure of the bell housing a bit, but for a light car, its probably not an issue. I prefer not to use those kind of cut cases when I can get away with it. This paticular tear down is going in an El Camino, so space is not an issue.

 

[Swims350]

oh ok I know what you mean now. Yea the headers for the MC hit that flange, right around the starter kickout part of the flange, I left it alone, they fit and bolted up but were right on that flange.

 

[zcampbell]

Hey im in the middle of my first TH350 disassembly and have got it down to the manual 1st and reverse clutch pack but can't seem to remove the ring holding it in. Any special trick to that or am I an idiot?

Very nice job with the step by step. I had no trouble disassembling and understand this trans thanks to this post.

 

[HotRodPC]

Now when you say ring, do you mean the snap ring? That one is pretty easy. Actually the easiest one to get normally. So that actually makes me think you're reffering to the pressure plate behind the snap ring. The pressure plate can be a bit challenging for 2 reasons. #1, the anti cluck spring holds pressure on it. #2, sometimes that pressure plate rocks in the case and chews on the case lugs, then the pressure plate sits behind the chewed on lugs. So to get it out sometimes, you have to figure out a way to work it back to where the lugs line up with the pressure plate, then it should come free with a little persuasion.

 

[82chevy350]

Im about to have to do this so my trans dont take a dump on me once i get my 383 finished.. You make it look so easy haha

 

[HotRodPC]

Th350's are easy. Just with any trans. Lots of patience so you don't tear or fold over lip seals, get in a hurry and leave out thrust washers, torrington bearings or snap rings and all should be well. Making sure you check end shaft plays should tell you you if you have forgotten thrust washers and some snap rings, air checks should tell you if you tore any lip seals.

 

[82chevy350]

ill defiantly be referring to this thread when i do!

 

[WVscottsdale]

Where did you get the special tool from for the low reverse piston

 

[HotRodPC]

I bought it at a Transmisison Parts supply store. You can also buy them on eBay. For my first few transmissions, I used a homemade tool out of a long bolt, with washers and nut. May have even been a piece of all-thread. It was slow and bulky, but for a 1 time use if you're not going to be building transmissions often, save your money. They're not cheap now days.

 

[Jason Deckard]

Hello everyone,

I am relatively new here, my name is Jason. I have built 2 and 3 speed transmissions for going on 30 years. They make some nice tools if your going to be doing a lot of them. Some tools are required to keep from damage when disassembling and more importantly when putting things back together. The tools are not that expensive. there are a set slide hammers that make front pump removal a breeze. These hammers will work on both 350/400 since front pump removal is the same. Don't forget to replace all the bushings before putting back together. I have a neat bushing driver set that works on 20 different transmissions. If anyone needs any help, let me know. Ive probably experienced any question you guys could ask. I also have a lot of parts.