StevenH Posted December 9, 2007 Share Posted December 9, 2007 I was asked a few times how this can be done so here's how I am doing it... I have a 2wd 4" tailshaft th400 and a CJ7 long tailshaft Dana 300. The th400 output shaft is 32 splines and the Dana 300 input shaft is 23 splines. Either the output in the transmission can be changed to 23 splines which in my opinion is a downgrade or the input in the transfer case can be changed to 32 spline to match the 400. I got Advance Adapters to machine a 32 spline input shaft for me, it will take 15 minutes to install from start to finish. The outside diameter is the same, it's just the inner splines that are different from the stock shaft. The transfer case now has to be coupled to the rear of the transmission, if your tailshaft housing is round bolt pattern it will be a bolt-on maybe with some clocking issues but a clockring will fix that. Mine is a 2wd transmission so my tailshaft housing will have to be changed. JB Conversions builds 32 spline inputs for the Dana 300 also and Novak sells 23 spline output shaft for the th400. Novak claims their setup is stronger than 32 spline because the input shaft in the Dana 300 is female and enlarging the input leaves the outside thickness of the shaft thinner than they think it should be. Link to comment Share on other sites More sharing options...
oldjeep Posted December 9, 2007 Share Posted December 9, 2007 Whats the reason for the TH400 behind a 4.3L? The parasitic power loss is around 20%, and you will really notice it behind the V6. Might be better off with a Th350 or 700r4 to D300, they are a lot kinder on the HP drain. Link to comment Share on other sites More sharing options...
FxRacing282 Posted December 9, 2007 Share Posted December 9, 2007 Whats the reason for the TH400 behind a 4.3L? The parasitic power loss is around 20%, and you will really notice it behind the V6. Might be better off with a Th350 or 700r4 to D300, they are a lot kinder on the HP drain. whered you get a 4.3 out of all that? Link to comment Share on other sites More sharing options...
Kenosha Warrior Posted December 9, 2007 Share Posted December 9, 2007 his sig lists a 4.3L/TH400/D300 buildup for his mj. Link to comment Share on other sites More sharing options...
StevenH Posted December 9, 2007 Author Share Posted December 9, 2007 Whats the reason for the TH400 behind a 4.3L? So I can sleep good at night knowing I will never have to worry about my tranny breaking Link to comment Share on other sites More sharing options...
StevenH Posted December 9, 2007 Author Share Posted December 9, 2007 I didnt explain the application either. It will be a rock toy, low range most of the time. 4.88 gears on 35" tires, the truck should be fairly light. If the transmission does lose 20% of power and the 4.3 makes 200 hp that would still leave me with 160hp. Probably more than plenty for what I need it for. How much does a th350 or 700r take? It doesn't matter either way, I'm still using a 400 :cheers: I think I have heard that going from a 350 to a 400 in the 1/4 mile will make you lose a tenth. Link to comment Share on other sites More sharing options...
89Tonto Posted December 9, 2007 Share Posted December 9, 2007 Will there be any special drilling needed or will the clocking ring resolve most issues? Thanks... Link to comment Share on other sites More sharing options...
oldjeep Posted December 9, 2007 Share Posted December 9, 2007 I didnt explain the application either. It will be a rock toy, low range most of the time. 4.88 gears on 35" tires, the truck should be fairly light. If the transmission does lose 20% of power and the 4.3 makes 200 hp that would still leave me with 160hp. Probably more than plenty for what I need it for. How much does a th350 or 700r take? It doesn't matter either way, I'm still using a 400 :cheers: I think I have heard that going from a 350 to a 400 in the 1/4 mile will make you lose a tenth. That's 200 peak HP at a pretty high RPM, you'll want to look at the HP curve down in the 1100 RPM range. You won't have to worry about ever breaking it though;) I used to have a TH400 behind a 225 buick v6 in my old CJ, and you could feel the lack of power that it caused - and the 225 has a lot more low end torque than a 4.3 Vortec, My buddy runs a TH350 behind a 502 in his chevelle drag car, so it's probabally strong enough for a 4.3 ;) Good luck though, using factory adaptors is the cheap way to go. Link to comment Share on other sites More sharing options...
FxRacing282 Posted December 9, 2007 Share Posted December 9, 2007 I didnt explain the application either. It will be a rock toy, low range most of the time. 4.88 gears on 35" tires, the truck should be fairly light. If the transmission does lose 20% of power and the 4.3 makes 200 hp that would still leave me with 160hp. Probably more than plenty for what I need it for. How much does a th350 or 700r take? It doesn't matter either way, I'm still using a 400 :cheers: I think I have heard that going from a 350 to a 400 in the 1/4 mile will make you lose a tenth. if you get a 700R4 plan on staying up at night not knowing if your tranny will break. my friend has blown a handfull up. a TH350 with a NP205 run by a 4.3 will bring you where you need to go. it is possible to build 4.3's up and make them pretty darn sick. my frind had a sanoma with a 5 speed powered by a 4.3 and it would burn tires all day... not sure if that means anything to you though Link to comment Share on other sites More sharing options...
StevenH Posted December 9, 2007 Author Share Posted December 9, 2007 The biggest factors involved in me using the th400 is... 1. I already had it 2. In case I want to swap in a 350 engine 3. Bulletproofness with the 4.3 I'm easy on stuff anyways, a th350 would have easily held up. But I want to hear the numbers of power loss through a th350. I bet it's close to 20%, maybe 12-15% Link to comment Share on other sites More sharing options...
StevenH Posted December 9, 2007 Author Share Posted December 9, 2007 I have found some people that have studied this topic. The overall weight difference from a th350 and 400 is 10lbs. The rotating mass difference is also 10lbs. This guy claimed to have weighed both rotating components http://www.nastyz28.com/forum/showthread.php?t=58199 I also read where one guy seen no measurable difference at the dragstrip between a th350 and 400. Link to comment Share on other sites More sharing options...
oldjeep Posted December 9, 2007 Share Posted December 9, 2007 Normally they say that a TH400 takes 50 HP and a TH350 takes 35 HP to run. Normal Gearing: (Although there are some variations) 350 - 2.52 1.52 1.00 400 - 2.48 1.48 1.00 TH400 Dry weight is about 190lbs + 13 quarts (THis one I can verify, since I have shipped a TH400) Th350 is about 140lbs + 11 quarts of fluid Link to comment Share on other sites More sharing options...
StevenH Posted December 9, 2007 Author Share Posted December 9, 2007 I just weighed my th400 transmission is 135.6 lbs w/out TC and full of fluid TC is 35.4 lbs w/fluid Link to comment Share on other sites More sharing options...
FxRacing282 Posted December 10, 2007 Share Posted December 10, 2007 Normally they say that a TH400 takes 50 HP and a TH350 takes 35 HP to run. Normal Gearing: (Although there are some variations) 350 - 2.52 1.52 1.00 400 - 2.48 1.48 1.00 TH400 Dry weight is about 190lbs + 13 quarts (THis one I can verify, since I have shipped a TH400) Th350 is about 140lbs + 11 quarts of fluid a guy up the woods from me runs in maine mug bog assc. and he was a 350-->TH400-->NP205 and he runs in 3rd gear so id say a th400 is better. plus you have more selectable ranges and better effiency Link to comment Share on other sites More sharing options...
StevenH Posted December 10, 2007 Author Share Posted December 10, 2007 if you get a 700R4 plan on staying up at night not knowing if your tranny will break.I have killed 'em myself Link to comment Share on other sites More sharing options...
oldjeep Posted December 10, 2007 Share Posted December 10, 2007 a guy up the woods from me runs in maine mug bog assc. and he was a 350-->TH400-->NP205 and he runs in 3rd gear so id say a th400 is better. plus you have more selectable ranges and better effiency Huh? 3rd gear is 1-1 on both of them how do you figure better efficiency? Link to comment Share on other sites More sharing options...
StevenH Posted December 10, 2007 Author Share Posted December 10, 2007 There's no doubt about it, when I am all the way in the back of Tellico and it's getting late... the th400 will be the last thing I am worrying about. Actually my 4.3 has less than 10,000 miles on it, I picked it up myself new in the crate so I know what I have there. I tore the d300 down and it didn't need anything. I sealed it back up and siliconed the bolt head and threads and will put fresh gear oil in it after I swap the input. The 9" rear has 28 splines but by the time the truck is going I should have Moser 33 spline shafts or maybe 35 spline if they think I can run them... I'm letting them decide. I will have a d44 front, not exactly hardcore but not a crap axle either. All of this with 35/12.5 15's..and with my driving style (I crawl) it ain't gunna break 8) Link to comment Share on other sites More sharing options...
carnuck Posted December 10, 2007 Share Posted December 10, 2007 Whats the reason for the TH400 behind a 4.3L? So I can sleep good at night knowing I will never have to worry about my tranny breaking I have killed a TH400 with an Iron Duke in front of it. Of course it had a turbo and NO2! LOL! Link to comment Share on other sites More sharing options...
StevenH Posted December 11, 2007 Author Share Posted December 11, 2007 Whats the reason for the TH400 behind a 4.3L? So I can sleep good at night knowing I will never have to worry about my tranny breaking I have killed a TH400 with an Iron Duke in front of it. Of course it had a turbo and NO2! LOL! How much HP were you putting out? And who built the transmission, you got your money back I hope :D Link to comment Share on other sites More sharing options...
carnuck Posted December 11, 2007 Share Posted December 11, 2007 Chev built the trans. Motor was @400 HP Link to comment Share on other sites More sharing options...
oldjeep Posted December 11, 2007 Share Posted December 11, 2007 Chev built the trans. Motor was @400 HP Poor thing must have been really worn out. 400HP at what kind of torque? What exactly broke? Link to comment Share on other sites More sharing options...
Kenosha Warrior Posted December 11, 2007 Share Posted December 11, 2007 my old neighbors 78 J-20 401/Th400/QT ate its transmissions regularly. and even though its got an AMC bellhousing bolt pattern, its still a chev th400 and methinks his problem was the T/C input shaft was wobbling loose and taking out the insides slowly Link to comment Share on other sites More sharing options...
StevenH Posted December 12, 2007 Author Share Posted December 12, 2007 Link to comment Share on other sites More sharing options...
StevenH Posted December 12, 2007 Author Share Posted December 12, 2007 You unbolt the input housing off of the d300, remove the snapring, remove the gear, remove the next snapring and the shaft and bearing comes right out. 15 minute job w/taking pictures. This will be my first project writeup and I took plenty of pictures :cheers: Link to comment Share on other sites More sharing options...
StevenH Posted December 12, 2007 Author Share Posted December 12, 2007 With a larger spline count, the shaft is thinner than stock.. here's a side shot and it shows there is still plenty of material left. Link to comment Share on other sites More sharing options...
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