Nealio240z Posted August 20, 2006 Share Posted August 20, 2006 Im currently running a TH-350 tranny and a R-200 diff with 3.90:1 gears. I think its geared too high. It will launch in 2nd gear from a stop light (because it doesent have enough drag to shift into 1st on a launch) My top end speed is 90 at 5000 rpm. At 50mph its running at 2800 rpm. If I change to the R-180 diff (3.33:1) will it be strong enough and give me the top end and still get off the line? Im running about 330 hp... Quote Link to comment Share on other sites More sharing options...
deja Posted August 20, 2006 Share Posted August 20, 2006 You can get a R200 at 354. I'm no expert but I don't think you want to attempt fate with a R180. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted August 20, 2006 Share Posted August 20, 2006 Going to a 3.36 rear will only drop your 50 mph RPM from 2800 to 2400. Your top speed will go to 104 mph. The spider gears are the weak point in an open diff R180's. so if you go with some form of LSD it will hold up reasonably well depending on how you drive But you will still be turning over 2400 RPM on the free way. Best to start saving up for some type of overdrive transmission. Probably not the answer you want to hear. Quote Link to comment Share on other sites More sharing options...
tannji Posted August 20, 2006 Share Posted August 20, 2006 I had a 240 with 350 SBC and the th350 tranny, with 4.11:1 gears, and a shift kit solved that problem nicely.... didnt help my RPMs, of course, but it allowed me to manually shift with the racheting bump shift, which I think was a Hurst. Drive worked fine normally, with the option of switching to the manual bump shifting when I "needed" to. Having run a similar 240 with SBC and the 700R4 tranny, I would never go back to the TH350... unless light to light ghetto racing was the only action my car saw. I drove the car from San Diego to Davenport, Iowa and averaged slightly over 26 mpg, the comfort and fun factor was better, and of course I was much happier with my cruising RPM range. Quote Link to comment Share on other sites More sharing options...
zed240au Posted August 21, 2006 Share Posted August 21, 2006 id just change the ratio in your r200 would think they be easier to get than the 3.336 ratio r180 any way But that said ive been running a r180 lsd behind my v8 for 10 or more years with know worries running 3.55 ratio the 3.36 are like rocking horse poo here in australia Yet a mate broke 3 r180 diffs in his warm 6 cylinder 240z but he was and idiot i mean i sold him my old vh commdore with strong diff in it lasted 220,000 km and he broke 4 diffs in that was only a warm 253 so i say the r180 will last if treat well but r200 would be a better bet Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted August 21, 2006 Author Share Posted August 21, 2006 By running @ high RPM it is overheating on long trips. Is there a cheap solution to a LSD... Like a diff swap that is closer to a R-180 ratio? I need top end. I cant change my tranny. And my tires are already 26" tall. What is the lowest gear ratio available??? Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted August 22, 2006 Share Posted August 22, 2006 Most R180's are 3:36. Some R200's did come with 3:36 ratios, but they aren't very common and people who have them seem to know what they are worth. This list shows some R230's diffs came in a 2.946 ratio. Would put your 50 MPH RPM at 2115. But expect to drop a grand or more doing an R230 swap. An even better list of diff ratios is on this site http://zhome.com/, about half way down the left had side click on "Index Of Technical Articles " I have seen several Z's where they swap a vette pumpkn in an otherwise stock rear suspension. Don't know what is involved with that swap, but you can get some high ratios in a vette rear. But probably not a cheap solution. Is there an aftermarket overdrive you can add to the back of the TH350? But once again, I imagine not a cheap option. My suggestion is just get a run of the mill 3.5 R200. 3.36 won't buy you much over the 3.5. The ultimate solution is a T56.... Quote Link to comment Share on other sites More sharing options...
COZY Z COLE Posted August 22, 2006 Share Posted August 22, 2006 What kind of radiator and fan do you have and come down to Fairfield, I'll give you a 3.54 R-200 for free plus a few parts that go with it...... LARRY Quote Link to comment Share on other sites More sharing options...
jakeshoe Posted August 22, 2006 Share Posted August 22, 2006 Second gear starts with a TH350 are indicative of a governor problem. You likely have a worn governor/bore or stuck governor weights. Worn bore and gov is common. If you remove the governor the lands should mic .800", no less and be smooth. Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted August 23, 2006 Author Share Posted August 23, 2006 It will start in 1st if I hammer it but it shifts very quickly to 2nd ( about 50 feet) The car doesnt downshift to first unless im really getting on it... Slow starts it will leave in second... I think it is gearing.. Anyone selling a 700R-4 or 5 speed tranny? Quote Link to comment Share on other sites More sharing options...
Paz8 Posted August 24, 2006 Share Posted August 24, 2006 A 700 R4 has a higher first gear than your 350 trans, will shift to second quicker than your current trans. If you need top end the only way out is a rear gear change and a overdrive trans. I'd replace the rear first with a r200 3.54 ratio and see how it works out. The flange on the rear of the drive shaft may also need to be replaced. Quote Link to comment Share on other sites More sharing options...
Georgia Flash Posted August 24, 2006 Share Posted August 24, 2006 Best to start saving up for some type of overdrive transmission. You can get a used 700R4 from a salvage yard cheap. Mine cost $325, just make sure you ask them for the correct year and they will hook you up. By the way, the Hybrid Bible, (JTR Manual) warns against the 350 tranny because of the higher RPM’s on the highway. “If you decide to use a Turbo-350 or Turbo-400 transmission, you will realize the mistake you made within 5 minutes on the freeway.†JTR Manual page 4-1, Seventh Edition Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted August 24, 2006 Author Share Posted August 24, 2006 Okay thanks for the hint.. Can I use the same drive shaft and tranny mount from the TH350 with the 700r4? I plan on changing it out to a 700r4. Will it all bolt in? Thanks for the help... Quote Link to comment Share on other sites More sharing options...
Georgia Flash Posted August 25, 2006 Share Posted August 25, 2006 If I am not mistaken, the TH350 is a little shorter than the 700R4 so you would have to have the drive shaft shortened a little. That is not that big of a deal to have done. If you have a drive shaft business close by they can custom make you a drive shaft from scratch that will be cheaper than a shaft from lets say MSA. I found out this the hard way by buying the drive shaft that MSA sells that is supposed to be “bolt on.†It was not of course and I had to take it to the drive shaft shop to be shortened. The guy there asked me what I paid for the MSA drive shaft and when I told him, he laughed. In addition, I think that the TH350 mount will work with the 700R4 if I remember correctly. Here is a helpful link for the 700R4 transmission and others: http://www.bowtieoverdrives.com I hope this info helped you out a little. Quote Link to comment Share on other sites More sharing options...
Paz8 Posted August 25, 2006 Share Posted August 25, 2006 Your going to also need a lock up torque convertor if you don't already have one. The lock up needs to be working if your going to drive at interstate speeds or that 700 r4 will over heat. Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted August 29, 2006 Author Share Posted August 29, 2006 Anyone have a 700r4 for sale? Now I really want an overdrive tranny... Thanks for the help. Quote Link to comment Share on other sites More sharing options...
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