Which trans for temporary use behind healthy torque a 2004R or a TH350?

[olds307 and 403]

As I move closer to building my 424 SBO for my 70S, the motor itself doesn't bother me as much as the trans and rear. I know the motor will be 400+ HP and 500 ft/lbs. My long term goal to lay down the hammer on all but the highest power modern muscle cars is a beefed up 2004R with billet parts and 3.90 gears and posi in the Type O in my 70S. Gear multiplication is a huge reason modern cars are so fast, I need at least 4 gears and OD to compete. Currently it has a 2.78 open ratio along with 28" tall tires means a liveable 2250 at 60 mph. I have a good shifting stock 2004R with a deep pan and a 2300 stall about the minimum I would run, should stall a bit higher with more power. Will a CK billet servo and shift kit help this trans live more than a day? I not sure if the Transgo shift helped much but on the one, the converter imploded and the other I set the band too tight with the Billet servo. The last 2004R was ran low due to a crappy, leaky Hughes pan and a rolled dipstick seal. Still have that trans for available parts and can get more cores. I can also get a used BOP TH350 from the same wrecker. How much power would a good used TH350 take with a Transgo shift kit? I don't want to go the TH400 route, too much modification. I am not a fan of TH350 stock, saw two fail behind 165 HP of mid 70's Olds 350 power, one had 158,000 miles. I also saw one last about a day behind a stock mid 70's 454 truck motor dropped in a Camaro. He through a used one in with shift kit, lived for a while at least. Is the TH350 with a Transgo kit the way to go short term? I would also throw in a Jegs 2300 to 2700 stall converter. I have a governor for both trans that are better than the stock 4000 rpm shifts, well 3000 on the current 2004R. I am not a TH350 fan, so other than inconvenience, I don't care if it breaks. Does it have a better chance of living than the 2004R? Thoughts?

 

[fleming442]

How about a stout TH350, then add a Gear Vendors later?

 

[lilbowtie]

Currently it has a 2.78 open ratio along with 28" tall tires means a liveable 2250 at 60 mph.

That doesn't make sense, if you are running a 200r4 do the math and you should be @ 2050 in third (1 to 1) @ 60mph and about 1450 rpm in OD

 

[olds307 and 403]

That doesn't make sense, if you are running a 200r4 do the math and you should be @ 2050 in third (1 to 1) @ 60mph and about 1450 rpm in OD

That is in 3rd WITHOUT the torque converter locked up. Yes, it runs 1380-1400 rpm at 60 mph in OD, torque converter locked up. You guys keep saying 200 rpm with compared to without for lock up. All my trans are 250 to 300 rpm less locked up. Yes, I checked the speedo with a GPS.

 

[UC645]

Why not stick a hardened sprag race in the TH350 and abuse it until you’ve got the 200 4R built?

 

[olds307 and 403]

An option but is a hardened sprag enough in an otherwise stock TH350 with a shift kit? Another option is my current 2004R with the CK shift kit, billet servo, 10 vane pump and a billet foward drum and welded shaft. Pretty deep dive inside at that point, it looks like it was rebuilt at some point, hard to say how long ago and the actual condition inside. I just don't want to go too deep into either trans but maybe it would be easier, getting some of the parts for the 2004R. If it fails, then a total rebuild. The hardened sprag on a TH350 is fine but what about machining the direct drum for one more clutch and steel? Then bushings are known to go etc, where do you stop? I do have the original TH350 that had a weak reverse, I could rebuild it vs buying a used working TH350. I just don't want much in it, I can dissect it and see what it needs. Options for sure.

 

[UC645]

An option but is a hardened sprag enough in an otherwise stock TH350 with a shift kit? Another option is my current 2004R with the CK shift kit, billet servo, 10 vane pump and a billet foward drum and welded shaft. Pretty deep dive inside at that point, it looks like it was rebuilt at some point, hard to say how long ago and the actual condition inside. I just don't want to go too deep into either trans but maybe it would be easier, getting some of the parts for the 2004R. If it fails, then a total rebuild. The hardened sprag on a TH350 is fine but what about machining the direct drum for one more clutch and steel? Then bushings are known to go etc, where do you stop? I do have the original TH350 that had a weak reverse, I could rebuild it vs buying a used working TH350. I just don't want much in it, I can dissect it and see what it needs. Options for sure.

If your 200 has that much done to it, throw a billet output shaft and a fresh set of clutches at it and be done with it. Can’t tell if the planetaries are upgraded without pulling it apart however, those could prove to be the weak link if they’re not the factory upgraded ones at the least.

 

[lilbowtie]

Rather than temp you should decide on which trans you prefer and go with it. I personally like the th400, have built quite a few and 3 with trans brakes - never lost one. The 350, with a good shift programming kit, a wide direct clutch drum bushing, and a hardened intermediate roller clutch outer race (or better yet B&M's 36 element sprag) and you have something. I don't have much experience with the 200r4 other than the problems my buddy has had with his GN.
I know we have been chit chating a little and I hope I'm not coming across as a know it all - if so I can fix that.

 

[olds307 and 403]

I am going with the 2004R long term. I can find a used TH400 with a warranty but I would need a yoke and driveshaft. There is nothing done to this trans by me, I believe a 86 model out big car is what decoded as, a yellow tag. I bought it with a 73 Olds 350. Only thing special is the deep pan/4L60E filter and a PATC base model 2200 to 2500 high stall torque converter I had lying around. Normal soft, stock shifts. That why I have the line pressure cranked up, added zip ties till I got full pull at full throttle after properly setting the TV cable. A 83 non CCC Qjet and proper factory TV bracket is being used along with the crank the throttle by hand and push the button to set. Neither trans has any internal performance upgrades that I know of. The fluid was super nice and red along with very little debris in the pan. There was a rebuild tag on the 2004R torque converter. Just don't know what was done to the trans or how long ago, I assume a rebuild was done. I have been told by a couple of knowledgable people they died around 130,000 km often. The original TH350 and a TH350C I have both need rebuilds.

 

[UNGN]

My T-type had a 100K mile stock 2004R with a shift kit ran mid 11's @ 115-118 for years while shifting at 4800 RPM, so math says it was making a lot of torque. I wouldn't worry about one behind any NA motor under 450 cubes unless you are towing or trying to use a trans brake.

The TH200 expect from South Africa who installed my shift kit (when the car ran 14's in the mid 1990's) said that if the trans his high mileage, NEVER change the trans fluid. He strained the old Fluid through panty hose and put it back in the trans. He said most of the 2004R rebuilds he did were shortly after the owners changed the fluid/filter and the ph difference in the fluid dislodged dirt and unsealed seals