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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / June 2006th350 question
if you turn the output shaft (driveshaft) should the input shaft turn? I don't think so, but this one does. Even in reverse, it turns the same direction as the output shaft - shouldn't that be the other way? Park still works... It's the old (broken) th350 from my dirt track Camaro. I've got another one in the car, but now I'm trying to decide what to do with it. Locally to rebuild is around $600CDN. I can purchase a rebuilt kit for around $200 and I have a manual and have done one in high school (many years ago, under supervision, didn't have to work) or I can just buy a "new" one from a place like summit for $650 US. We might tear it down just for fun. Curious to see what I've done to it. Want a spare, but not going to pay the same as a new one... How feasible is it to rebuild one in a DIY-er world? Like I said, I have a GM overhaul manual, but I don't own a micrometer and don't have much of a machine shop... but I have done bearings on a small block and stuff like that... Ray > if you turn the output shaft (driveshaft) should the input shaft turn? > I don't think so, but this one does. Even in reverse, it turns the same [quoted text clipped - 17 lines] > > Ray I know how to rebuild transmissions. I teach it to my students. I have all the right tools. BUT, I only do it about once every year or two and it usually kicks my a.s. There are a number of skills involved that need practice if you are going to rebuild or a transmission successfully the first time every time. I'm not saying you can't do it. If you have good enough instructions and are a bit lucky you might only have to take it out two or three times before you get it right. <grin> If you like playing with that sort of stuff it might be worth a shot, but don't count on having a quality rebuild your first time.  SignatureKevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green <grin> If you like playing with > that sort of stuff it might be worth a shot, but don't count on having a > quality rebuild your first time. You can say that again! >if you turn the output shaft (driveshaft) should the input shaft turn? Any motion will be strictly from miscellaneous oil and aother drag. Without the front pump spinning and pumping fluid to engage clutches and bands hydraulically you can't select a gear. I have run T350 on dirt also. If you run in 1st tell whoever rebuilds it that you don't give a damn about 2nd or 3rd! FWIW a THD200 non-overdrive is 50 pounds lighter. Whatever anybody will tell you it WILL hold up fine in 1st. I ran one behind an OLDS 403 for several years with no problem. Its reputation for being weak is 2nd gear. It will buzz your motor about 4-500 rpms faster in 1st relative to the TH350. Might or might not be a good thing! I used mine with a 2.41 rear and fairly tall tires and ran a 3/8 mile tacky fast dirt track. >I don't think so, but this one does. Even in reverse, it turns the same >direction as the output shaft - shouldn't that be the other way? Nope, means nothing! > Park still works... Yes it will. >It's the old (broken) th350 from my dirt track Camaro. I've got another >one in the car, but now I'm trying to decide what to do with it. >Locally to rebuild is around $600CDN. I can purchase a rebuilt kit for >around $200 and I have a manual and have done one in high school (many >years ago, under supervision, didn't have to work) or I can just buy a >"new" one from a place like summit for $650 US. A lot of what one would to do a transmission for street performance means nothing on your oval dirt track car. Don www.donsautomotive.com >We might tear it down just for fun. Curious to see what I've done to >it. Want a spare, but not going to pay the same as a new one... [quoted text clipped - 5 lines] > >Ray > FWIW a THD200 non-overdrive is 50 pounds lighter. Whatever anybody > will tell you it WILL hold up fine in 1st. I ran one behind an OLDS [quoted text clipped - 3 lines] > mine with a 2.41 rear and fairly tall tires and ran a 3/8 mile tacky > fast dirt track. Mmmm.... I got a free TH200 that came from a 77-78 Nova that might be useful then. I was worried it wouldn't hold up. I do run an enduro class - 200 laps on a 4/10 mile track in a heavy (3200 pounds without driver) Camaro. FWIW, the Summitracing $650 trans has a manual valve body and no vacuum modulator. The last race I only had second gear. What happened was it would idle fine in park and when you'd put it in gear it would just die. Trying to go up the trailer was murder. I just thought it was cam or idle or something because once you'd be rolling it would be fine. When we pulled onto the track to line up it started dying in gear again, so I tried putting it into neutral... and had no neutral. Of course, then the race started, so I was off... and realized it was running only in second. After 20 laps it started slipping, so I pitted thinking it was a linkage problem & a fluid problem (I've busted a tranny line before and lost all the fluid)- shut the car off... linkage was fine - restarted, now I had only neutral - we put it in the air and moved the linkage on the tranny, nothing in any gear. Fluid was full. I'm assuming I probably just cooked the internals from abuse. Ray >> FWIW a THD200 non-overdrive is 50 pounds lighter. Whatever anybody >> will tell you it WILL hold up fine in 1st. I ran one behind an OLDS [quoted text clipped - 11 lines] >FWIW, the Summitracing $650 trans has a manual valve body and no vacuum >modulator. A good transmission man can set up your box just for the gear -- 1st or 2nd I assume -- that you race in. he will set up the line pressure maxed out for best holding pressure on the clutches. I ran automatic for about 8 years and just used junkyard transmissions. I lost a couple of torque convertors so I would have them refurbished before the racing season. >The last race I only had second gear. Is that your gear of choice? On a 4/10 it might be. I don't know what your rear gear is. The THD-200 won't hold up in second. > What happened was it would idle >fine in park and when you'd put it in gear it would just die. Trying to >go up the trailer was murder. I just thought it was cam or idle or >something because once you'd be rolling it would be fine. Torque convertor cratered. Probably filled the transmission with trash when it did so. > When we >pulled onto the track to line up it started dying in gear again, so I >tried putting it into neutral... and had no neutral. Of course, then >the race started, so I was off... and realized it was running only in >second. What did you want it in? Don www.donsautomotive.com > After 20 laps it started slipping, so I pitted thinking it was >a linkage problem & a fluid problem (I've busted a tranny line before [quoted text clipped - 4 lines] > >Ray >>> FWIW a THD200 non-overdrive is 50 pounds lighter. Whatever anybody >>> will tell you it WILL hold up fine in 1st. I ran one behind an OLDS [quoted text clipped - 22 lines] > Is that your gear of choice? On a 4/10 it might be. I don't know > what your rear gear is. The THD-200 won't hold up in second. The rear is a 2.43 IIRC. (or it might be a 2.56 - came with the car and never been swapped yet because other than cracking the welds I haven't busted THAT yet...) Running 235/60 or 235/70 on the back and usually running second gear. Why? Old stock engines (engine #1 was a 305) so I would hit around 4000 in second at the end of the straight, which works out to like 6700 in first and I just don't know if the old engines woulda held together at that speed. But the last race where the tranny fragged - all I had was second. In first I had second. In reverse I had second. In neutral I had second. That's why I thought it was a linkage problem at first and why it was so hard to get it on the trailer - try going from a dead stop up trailer ramps in second gear with a 2.43 gear. My new engine is nothing fancy - a Goodwrench 350 - rated for max hp @ 4300 rpm, so I might be sticking with second. Trade a bit of lap times for not blowing it up for 200 laps. We're allowed a .450 lift cam, this came with about 401 lift, so it's no screamer. I'm also thinking of trading torque for hp because we have to run stock manifolds and a 2 barrel carb anyway, so I'm thinking of "tuning for torque." And then after this race I'll probably order the 450 lift cam and valvesprings like all the front runners are. :) It just hurts because fancy cam #1 broke into 4 pieces when I lost oil pressure and fancy cam #2 got wiped when the balancer came apart and the engine grenaded. But, that's racing - nothing you can't fix with more money. (*and a skid plate under the oil pan so you don't run stuff over and smash the pan.*) My buddy knows a guy who does tranny rebuilds on the side - did the one for his Nova for pretty cheap... I'm trying to nag him to do mine... Thanks for your suggestions though. We'll see how things go next weekend. See what new and amazing ways I can find to break things. Ray |
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