Guest Hampton Posted August 30, 2009 Share Posted August 30, 2009 I'd like to replace my Turbo 400 transmission with a 200R4. The mount is in the same location on both transmissions so I'm hoping it will bolt right in. My question is on the driveshaft. The 200R4 is 3/4 of an inch shorter than the Turbo 400, is that significant enough to warrant having the driveshaft lengthened? Or can I swap on a 27 spline yoke and go with it? The car is a '70 402 with 12 bolt 3.31 out back. Greg Quote Link to comment Share on other sites More sharing options...
monte11sec Posted September 1, 2009 Share Posted September 1, 2009 Greg, I did this very same tranny swap and I had to purchase a different drive shaft (the original was going to be too short). I just took the necessary measurements and ordered a new driveshaft from Strange Engineering. I'll say this, as long as the TH2004R is built correctly, you're going to love it. It will cause the car to accelerate out of the gate harder due to the steeper 1st gear ratio (2.74 vs 2.48), it takes less power to turn the TH2004R than it does the TH400, the gear spread is still tight (as opposed to the TH700R4), and the highway cruising is much better. I'm running a 12 bolt with 3.73 gears and it made the car much more fun to drive on the highway and I am no longer getting passed by 18 wheelers while turning 3000 RPM at 60mph. Quote Link to comment Share on other sites More sharing options...
Dans '70 Z20 Posted September 1, 2009 Share Posted September 1, 2009 Be sure its a well built TH2004R. Only as of recently have they come out with aftermarket parts for them to withstand the torque of a big block. Stock ones have no chance. Pretty costly when built right and then you need TV cable and new converter. Cheaper route: Re-use/rebuild Turbo 400 and have them install 2:75 lower gear set. You will then have 2:75 first 1:57 Second and 1:1 third .......same as the first three gears on a TH2004R. If and when you want an overdrive add a gear vendors O'Drive to back of Turbo 400 ($2500). This way you get a known bullet proof Turbo 400 with lower gears and a bullet proof O'Drive unit in the Gear Vendors. It can shift into O'Drive at a certain speed automatically or can be switched to manual and manually shifted between gears ........1, 1 Over, 2, 2-Over, 3, 3-Over to better 1/4 mile time. New TCI: GM 4L80E 6 spd is currently having some problems. 700R4: really low 1st gear. No need for low end torque of a BB. 2nd hits so hard torque of a big block stresses 2nd gear. 2004R: known as a weak transmission has only recently had parts available to build above 400hp. We'll see. Turbo Regals going into 8's on 2004R's but they do not have the torque of big blocks. Turbo comes in at higher RPM so less stress on tranny. Looked into this in the past and thought I would share. The only benefit of going with 700r4, Ford AOD 0r 2004R is the ability to fully program shift points to maximize times at the track. Dan Quote Link to comment Share on other sites More sharing options...
monte11sec Posted September 1, 2009 Share Posted September 1, 2009 I know this is a bit off of the original topic but Dan is right, the TH2004R must be built correctly to stand up to the torque of a big block (or a seriously built turbo V6 for that matter). The Buick guys have used the TH2004R in 9 and 10 second Grand Nationals for years without problems. There are a hand full of builders that can really build a very durable TH2004R but it will cost quite a bit depending on the power level you want one of these transmissions to hold up to. I have read that many of these builders recommend going to billet input shafts and intermediate drums once the power level exceeds 400 HP and/or 400 lb/ft of torque. I'm sure many people have gotten away with using hardened parts instead of billet but I wonder if it is only a matter of time before a failure occurs. The TH400 can definitely be built to hold up to more power than a TH2004R and I have never heard of someone actually breaking a GV (they are basically bullet proof) but I think the price difference will be minimal between a seriously built TH2004R and a very well built TH400 with a GV on the back. I have read that several Buick guys have gone to TH400's after breaking a few TH2004R's but I think these are very low 9 second to high 8 second machines. I think the limit for a TH2004R is about 800 HP or mid to high 9's. Quote Link to comment Share on other sites More sharing options...
Dans '70 Z20 Posted September 1, 2009 Share Posted September 1, 2009 Yeah, you are right now that added up the numbers. Turbo 400 Street/Strip rebuild with lower gears $1500-1700 Gear Vendors: $2595 Total you would be at around $4000. A 2004R built for a big block with TV kit and torque converter, new shaft probably end up about the same cost. The benfit is you can outlay the cost in stages and add gear vendors later to put off expense. With 2004R your all in $$. Also with a Turbo400 you have insurance based on its historic abilities......the 2004R upgrades are only currently being put to the test. Dan Quote Link to comment Share on other sites More sharing options...
72MC Posted September 2, 2009 Share Posted September 2, 2009 New TCI: GM 4L80E 6 spd is currently having some problems. Dan The 4L80 6 speed may have problems but the 4L80 4 speed is a beast and is just as tough or tougher than its 3 speed sibling, the th400. It is not as heavy as everyone thinks either. I can pick it up just like a th350 or th400. However, with the 4L80 there is a length issue. It is longer than the th400 which in the Montes uses the last bolt holes for the cross member. There will need to be a fabrication performed for the crossmember. The main reason for my post is to say this, if you want a high hp handling tranny, you will need good parts and a good builder. My 4L80 full manual can handle 800hp to the rear wheels and has no computer or lock up convertor(has just a regular 3500 stall convertor). The input shaft is made of 300M metal and everything inside the case is custom made. Dan is right, a bullet proof tranny takes $$$$$$$, and more $$$$$$. The guys I used, Gearstar out of Akron, OH, can build you a bullet proof th2004r, but there again, it will take some $$$$. I originally was going to go that route and changed my mind to the 4L80. That being said, the gear vendor set up with a well built tranny is another excellent option. - Dave Quote Link to comment Share on other sites More sharing options...
Dans '70 Z20 Posted September 3, 2009 Share Posted September 3, 2009 Spoke to the "legendary" Art Carr today. Do not associate him with the company currently working under the Art Carr name in Texas. Original buyer of his empire paid down payment on business with an agreement to make good in three years on the balance. Needless to say he did not and sold business to a converter company out of Texas now working under the name Art Carr. He says they have a local AAmco dealer doing the trans orders. Anyway after a million dollars spent in legal fees he gave up the fight and started working with California Performance Transmissions. He says he has been building 200r4's to 800hp for 6 years. Has them on Grand nat'ls doing 9.5sec 1/4 mile times, 502/572 cars doing mid 11's etc. Says they have less rotating mass than the TH400,4L60,4L80 and therefore will help at the track. Says he has had many guys running them for years. Kit with everything is $2900. Spoke to Coan Performance (who I go my Torque converter from) and they disagree. They say if you want overdrive to swap out rear gear and put in a gear vendors. Says they have never seen one fail. They say the 2004R's are now built to handle more HP but will just take longer to break down. Stock TH400's can handle a BB without modification. They also recommended sticking with the stock gear set in the Turbo 400 rather than using the lower gear set. The Gear vendors unit only uses 1/4 hp per 100hp which is minimal. I'll stick with my Street/Strip TH400 and swap out rear gear to 3:73 and add a GV unit when I get the cash. Seems more reliable in the end. Dan Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted September 3, 2009 Share Posted September 3, 2009 I agree with you Dan, I think the TH400 is one of the most reliable units you can get. It's simple, strong, tried and true plus there is already tons of knowledge everywhere on how to make them work. For folks who want to go on road trips I can see the desire for some kind of overdrive and that's a matter of choice. For me personally I like to keep things as simple as possible and od just adds another variable I don't need. I'm not in a hurry these days, I don't need to go 75mph on the highway so a 3:73 or 3:42 is just fine. Most BBlk's are not high rever's, anything lower is questionable anyway unless some tall tires are out back. I have found that the desire to push for more rpm's doesn't always translate to faster times/speeds. If you have truly built a 7000rpm+ motor then that's a different story...JMO Quote Link to comment Share on other sites More sharing options...
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