olds 307 and 403

As I move closer to building my 424 SBO, 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? Thoughts?

matt69olds

Are you comfortable with transmission work? There is no reason a TH350 won’t live a long life behind your engine. I have built many that live just fine in 11 second cars with basically stock internals.

if your set on the overdrive trans, at the minimum get the hardened forward clutch housing. Install a hardened stator support tube in the pump. Upgrade to a 10 vane pump with hardened rings. Use a good band, servo, and valve body calibration. Make sure the TV cable is right.

oddball

Probably fine with either. The open rear with the steep gear and street tires means you'll burn rubber before stressing the trans.

Slicks with a posi is a completely different story.

I've had a basic rebuild TH350 with a shift kit, no special internal parts, sitting behind a 480ftlb engine for ... 2,000 miles? 3.73 posi with street tires, I'm very mean to it. Never missed a beat. Before that it was behind a decently built 350 for at least 15,000 miles.

I'd expect the 200-4r to live just fine, temporarily, as well. Just get the TV adjusted right.

FWIW, I was running 3.73's with the 200-4r. Highway cruise (75 mph around here) was right about 3k rpm. First gear went by *very* quickly, so I'm actually looking to go to steeper gears.

olds 307 and 403

I will be building the 2004R for this car, just the $2000 US price tag for parts for one to live is the only reason I won't build it at the same time. I am planning on the 2800 PTC torque converter Dr Dan uses. I may be around that 480 ft/lbs mark, 9.6 to 1 compression #6 heads with porting and 2"/1.625" valves along with a custom roller cam from Mark. Yeah, 3.90 gears are what I want, around 2200 rpm at 70 mph locked up with the 2004R and 275/60R15's, as fast as we drive legally here, well 110 km/hr. If the TH350 will live, no slicks or posi will get put on/in, I may go that way. I have done the pump mods, shift kit and the servo on a 2004R. If I go as far as a foward drum, aren't I awfully close to a full rebuild? Plus if I do the 3.90 gears, I do not want to go to a TH350 even for a short time. The nearest track is now hours away, wouldn't go till I have the 2004R and 3.90 gears. I also need headers, 2.5" exhaust, front half and a much better rad, all adds to the cost.

big man

Where are you getting a $2000 price tag? I got the forward drum, master rebuild 'B' kit, sun gear shell, 3rd clutch overdrive piston, bearing kit, 10 vane pump, and accumulator delete for close to $1200.
We are very close in builds. I've got 391 gears, 2004r, 2800 stall and a 455. Transgo kit with dual feed. I may be at 500 torque but I'm not doing slicks or drag racing which is why I didn't do billet 'everything'
I did have the 350 trans, which was good but I needed the overdrive. Can't say much about the 350 cause I haven't hammered on it but this 2004r since being built hasn't missed a beat! I don't baby it either.. I drive it to Drive It!

olds 307 and 403

Maybe I figured in a deep pan and complete overhaul with the converter. Is a hardened sprag enough in an otherwise stock TH350 with a shift kit? Maybe 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. Yeah, I forgot about the sunshell being very weak. 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. I would leave the 2.78 till I make sure the 2004R is good. I would hate 3.90 gears and a non lock up TH350. Options for sure, thanks guys.

69CSHC

I like it, I can feel the want and need to turn your ride into a beast !

As you said gearing is key these days, and since you have ruled out the TH400 which is really the only stock trans of the 3 that can handle that type of power aggressively. I say go with the built 200-4R. The hardcore GN guys have been going this route for a long time as far as I know with great results. I would just do the bare minimum to get the strength and reliability up to where you feel comfortable. I would think if its built to handle around 600 lb ft you should be able to beat the ever living hell out of it without much worries.



Disturbing.... especially considering my base 310 hp 350 has the highest torque rating for an Olds small block of all time. Wondering if the early TH350s versions are stronger than the later versions ?

Not to hijack your thread olds 307 and 403, but maybe you can help me understand the lock up and non lock up torque converter as this definitely changed over the years. The early versions like I have are non lockup. the late versions I believe 1979 and up are lock up. Advantages and disadvantages ?

olds 307 and 403

Advantage, 300 or so less rpm on the highway. Disadvantage, is it takes up some of the circuits so the dual feed mod for the direct clutches can't be done. Also the lock up torque converter costs about twice as much, especially higher stall with less available.

matt69olds

The TH350 for the most part didn’t change during its production run. They made some dimensional changes to the sun shell, replaced thrust washers with bearings, and replaced some aluminum parts with plastic to save some money. Machine the direct drum to fit five clutches, dual feed the direct drum, install a wide bushing in the direct drum, and a few valve body modifications, a 350 will handle some serious power. The key is not getting to aggressive on the 1-2 shift.

olds 307 and 403

The super hard 1-2 shift is where the sprag explodes correct? I could do the minimal upgrades to the 2004R, billet foward drum and welded shaft along with the CK shift kit servo and and even get their rebuilt pump and run it. With having a passable converter that flashes at 2350, it maybe similar cost to a full TH350 rebuild and converter. Have you seen sunshell failure? Supposedly a very weak stock sunshell in the 2004R. Minimal cost if I am ripping it half apart.

69CSHC

Thanks guys !

So I'm seeing that, non-lockup cost less, works harder, but can be built up easier for full tilt performance.

matt69olds

The earlier 2004R had sun shells that weren’t heat treated. I think after model year 84 they all got heat treat. It will be very obvious to tell visually, if the metal is a dark gray as opposed to shiny, the dark is treated.

If you decide to go with a 350, either run a stock intermediate roller clutch race, or buy one from a reputable source. Some of the cheap aftermarket races are entirely too hard (makes them brittle) they will shatter like glass. Friend bought a race from EBay, it broke early in its life. Destroyed the drum (obviously) and tore up the pump. He bought a core trans to get the pump and drum, put those used parts in it and never had another problem.

olds 307 and 403

Good to know about the hardened race. Either way, I am probably be looking at $1000 US or $1350 Canadian to build a trans. This an 86 trans, should be a hardened sun shell. I will probably do the 2004R and maybe buy the complete rebuild kit, CK foward drum, shaft and servo and maybe the complete pump. I will know if I need clutches and steels after disassembling the foward drum. I will at least buy the complete seal kit from CK. Last time I completed a pump upgrade, it must of had clearance issues. I needed a .555" boost valve to get 215/220 psi in the foward gears from 180 to 190. The CK pump should eliminate one variable, low line pressure. I noticed a huge shift quality difference going from 180 to 220. I would imagine another 75 psi would be that much firmer.