Guest macks Posted February 18, 2003 Share Posted February 18, 2003 G'day folks I'm changing my '76 260Z (australian delivered) auto gearbox for a manual. My mechanic says the car has an R200 3.545 rear end, and I'm in a spot of bother deciding what gearbox to go for... Option one: 4-speed of unknown origin, likely from a 240Z or 260Z*. Ran well until it was removed and put in storage for a few years. Cost of all parts for this conversion is less than A$200 (sub-US$100) Option two: 5-speed, likely from 280ZX as the donor car (260Z bought my mechanic for wrecking) has a L28, still in car and running strong. Cost of all parts is A$440 (~US$220). My mechanic suggests using the 4-speed as he thinks the taller diff of the auto isn't really suited for the 5-speed's overdrive gear, but I want to throw it into the ring for discussion. Since there's a considerable premium for the 5-speed, is it worth the extra money? It'll be in the car for 1-2 years until an engine conversion of a 'slightly' more powerful nature, but until then the car is stock, apart from koni's, coilovers and hilux calipers/skyline rear discs. The gearbox/engine will be sold then... Cheers! * = note that australia got different models/spec in different years than the US. How they differ, I don't know Quote Link to comment Share on other sites More sharing options...
Mike C Posted February 18, 2003 Share Posted February 18, 2003 I don't know about road speeds down under, but switching to the ZX 5 speed makes the car LOTS more driveable. You can keep up with traffic with sub 3k rpm engine speeds. Here I borrowed this chart on nissan trans based on US cars(!) from zhome.com: 72/76 two piece case U.S. Non-US F4W71B FS5C71B 1. 3.592 2.906 2. 2.246 1.902 3. 1.415 1.308 4. 1.000 1.000 5 n/a 0.864 RearGear 3.36 3.900 (72 thru 76) 77-79 1980 81-83 Borg Warner T-5 {Turbo Only] 1 3.321 3.062 3.062 3.500 2 2.077 1.858 1.858 2.144 3 1.308 1.308 1.308 1.375 4 1.000 1.000 1.000 1.000 5 0.864 0.773 0.745 0.780 Check out the T5. The best all-around trans IMO. Has the low first gear compareable to the early US 4 speed but almost as much OD as the ZX late 5 speed. The T5 and 3.54 have an overall first gear of 12.39. Compared to the late ZX 5 speed which has a 11.94 using 3.90! The T5 and 3.54 is effectively 2.76 in 5th while the ZX/3.90 combo is 2.9055. Do a little math and figure out what is best for you and what your long term plans for your car will be. I bought a T5 for my car. Even switching to 3.70 LSD will have less effective gear ratio on the highway than the 3.90 and ZX 5 speed. THe US 4 speed and 3.36 geared R180 give a 12.01 1st gear, almost same as the T5. I know you didn't ask specifically about the T5, but IMO, it's the best all around for a driver, at least with the addition of an aftermarket shifter. Quote Link to comment Share on other sites More sharing options...
jeffp Posted February 18, 2003 Share Posted February 18, 2003 I would agree with the T5 Borg Warner box as well. I drive a zx car and it had the 3.54 diff gear and the T5 I had good power, and very good fuel economy as well. I could drive about 400-450 miles on 21 gallons of gas. I thought that was good myself. Quote Link to comment Share on other sites More sharing options...
Mike C Posted February 18, 2003 Share Posted February 18, 2003 I guess I should have specified a few gear ratios as well. My original understanding was that 4 speed cars came to the US, and everyone else had a 5 speed all along. I know that was true in Europe and Japan, maybe Oz is same as US? The manual trans 240's in the US were all equipped with 3.36 R200. The manual trans 260's usually had 3.36. The manual trans 280 and 79 280zx had 3.54 while the 80-83 cars had 3.90, except the 3.54 geared turbo 82-83 cars. 81 turbo could not be had with auto. As you can see, there is nothing wrong with the 3.54 with a manual trans, it just depends on the trans. I have 3.54 in my car with what I think is a late 5 speed. It could use more first gear, but the OD more than makes up for that! I'm really looking forward to both with the T5. Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 18, 2003 Share Posted February 18, 2003 I think the late model NA trans is better, just for sake of having a set of close ratio gears. The gear spacing of the T5 is not really performance oriented as far as shifting goes. In the meanwhile I have an early 5 speed, which is about like having two 4th gears. Quote Link to comment Share on other sites More sharing options...
Guest zline Posted February 19, 2003 Share Posted February 19, 2003 T5 is superior in all aspects and anyway it has 5 gears Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 19, 2003 Share Posted February 19, 2003 With my early 5 speed, I'm in 3rd gear before 20MPH, first gear is worthless. If my speedo is accurate though, someone put some 4.10s in the friggin car, I'll find out someday. Quote Link to comment Share on other sites More sharing options...
Guest zline Posted February 19, 2003 Share Posted February 19, 2003 With my early 5 speed, I'm in 3rd gear before 20MPH, first gear is worthless. If my speedo is accurate though, someone put some 4.10s in the friggin car, I'll find out someday. why dont you just take down the rear end one weekend and take a peek at the speedo gear and see if its the correct one? I could help you with that just you live on the other end of the state....i feel so alone being a z head down in socal... *edit* just be happy you dont have 4.56s like my dads nova does...even with a 3300 stall and a 11" torque converter and reverse manual valve body stuffed into a TH400 trans...you cant go more than 60 miles at a time....but then again that 60 miles is at about ~110mph w/o breaking a sweat 13.1:1 compression 383 nova anyone? Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 19, 2003 Share Posted February 19, 2003 why dont you just take down the rear end one weekend and take a peek at the speedo gear and see if its the correct one? I could help you with that just you live on the other end of the state....i feel so alone being a z head down in socal... I know, call me lazy Unfortunately the exaust is routed RIGHT under the freaking rear end. I heard that other cars are this way as well, its so bad that I can't jack it up without twisting the body, I need to cut that peice of ___ off sometime so I can work on the car without destroying it. I've met one person from the LA area to pickup an F54, and there is at least one other down there who really knows his Z cars, he's on the board (IanZ)... If anything I'd think there are more guys and more good yards down there from the sounds of things. I cruise on the freeway 70 MPH @ 3400, 195/60 15" Its not TERRIBLE, but when I can get some more grunt in the car (turbo 2.8L) I'll throw in a 3.54 rear and look for a later 5 speed at some point with a real 5th gear. Quote Link to comment Share on other sites More sharing options...
Guest zline Posted February 20, 2003 Share Posted February 20, 2003 why dont you just take down the rear end one weekend and take a peek at the speedo gear and see if its the correct one? I could help you with that just you live on the other end of the state....i feel so alone being a z head down in socal... I know' date=' call me lazy Unfortunately the exaust is routed RIGHT under the freaking rear end. I heard that other cars are this way as well, its so bad that I can't jack it up without twisting the body, I need to cut that peice of ___ off sometime so I can work on the car without destroying it. I've met one person from the LA area to pickup an F54, and there is at least one other down there who really knows his Z cars, he's on the board (IanZ)... If anything I'd think there are more guys and more good yards down there from the sounds of things. I cruise on the freeway 70 MPH @ 3400, 195/60 15" Its not TERRIBLE, but when I can get some more grunt in the car (turbo 2.8L) I'll throw in a 3.54 rear and look for a later 5 speed at some point with a real 5th gear.[/quote'] Im not sure if its a straight bolt in but I believe a J30 has a 3.5456 rear end im not even sure if thats it gear ratio but im 90% sure...im surprised more of us dont convert to using subaru R180 3.90 diffs...we wouldnt have to modify the m. bar when installing it since its the same pumpkin style. Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 20, 2003 Share Posted February 20, 2003 I've got a 3.90 right now (on a shelf), but thats for sale. I have a 3.54 that will come out of a turbo car I have, since I'll have the TQ to pull it, and I can stay in the gear longer on course this way. For an NA car though, yeah I would have wanted the 3.90. Quote Link to comment Share on other sites More sharing options...
Guest zline Posted February 20, 2003 Share Posted February 20, 2003 I've got a 3.90 right now (on a shelf), but thats for sale. I have a 3.54 that will come out of a turbo car I have, since I'll have the TQ to pull it, and I can stay in the gear longer on course this way. For an NA car though, yeah I would have wanted the 3.90. nah i'd shoot for a higher gear like a 4.10 hehe call me crazy but i like to rev fast Quote Link to comment Share on other sites More sharing options...
johnc Posted February 20, 2003 Share Posted February 20, 2003 im surprised more of us dont convert to using subaru R180 3.90 diffs... Thought the Subies ran mostly R160s. I was under a 2002 WRX the other night and it has an R180 in the rear, but the snout is longer then the snout on a 240/260/280 R180. It also has a different front mount casting. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 20, 2003 Share Posted February 20, 2003 I've got a 3.90 right now (on a shelf), but thats for sale. I have a 3.54 that will come out of a turbo car I have, since I'll have the TQ to pull it, and I can stay in the gear longer on course this way. For an NA car though, yeah I would have wanted the 3.90. There isn't a racetrack in the states of California, Nevada, or Arizona where you would want to run a 3.54 over a 3.90, regardless of engine torque or horsepower (except maybe the California Speedway oval or the full tri-oval at PIR). A 3.90 is the PERFECT rear end gear for T-Hill and a 4.11 is said to be perfect for Sears. Now that I've said that, is the 3.90 you're talking about an R180? Quote Link to comment Share on other sites More sharing options...
Guest zline Posted February 21, 2003 Share Posted February 21, 2003 I've got a 3.90 right now (on a shelf)' date=' but thats for sale. I have a 3.54 that will come out of a turbo car I have, since I'll have the TQ to pull it, and I can stay in the gear longer on course this way. For an NA car though, yeah I would have wanted the 3.90.[/quote'] There isn't a racetrack in the states of California, Nevada, or Arizona where you would want to run a 3.54 over a 3.90, regardless of engine torque or horsepower (except maybe the California Speedway oval or the full tri-oval at PIR). A 3.90 is the PERFECT rear end gear for T-Hill and a 4.11 is said to be perfect for Sears. Now that I've said that, is the 3.90 you're talking about an R180? um you'd never be in the power band with a 4.11 gear on a turbo car it'd rev way to quick....3.54 for a turbo app is awesome Quote Link to comment Share on other sites More sharing options...
Mudge Posted February 21, 2003 Share Posted February 21, 2003 Now that I've said that, is the 3.90 you're talking about an R180? No, its an R200 I bought. I will look at the numbers again, but I want to stay in 4th gear on the tracks, 5th gear maybe with a stronger trans. I dont know that I'll expect to hit 174 at Willow Springs (I'd probably crap my pants), but I like having headroom, especially if I ever take it to Silver State, although that dream may never happen. I want my torque to pull me, not my gear. But I'll take a look at the numbers again. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 21, 2003 Share Posted February 21, 2003 I want my torque to pull me, not my gear. But, but, but... At the rear wheel it doesn't matter where the torque comes from. A rear end gear's job is torque multiplication. When you gear a car for a road race track, you start with a rear gear the gets you to your track or aero limited top speed at the end of the fastest part of the track. From there you make compromises in rear gearing (assuming you can't or don't want to change transmission gears) to get the fastest corner exit speed onto the start of that same fastest part of the track. Then you might make further compromises to keep from being in-between gears at other critical parts of the track. While you're doing this you are ALWAYS checking lap times and making changes to get the fastest lap. In a 240 its common to have to feather the throttle at 7,000+ rpm in top gear (1.1 on a 4 speed) at some point on the track because you've run out of gear. With a 5 speed and its overdrive you can probably drop you rear end gear one step. FYI... on my NA 3L I'll be mostly running a 4.11 gear with my .87 overdrive 5th. The engine has a soft redline of 7,500 and was built as a torque motor so its horsepower and torque curves are very similar to a 300 hp turbo motor. Quote Link to comment Share on other sites More sharing options...
Guest zline Posted February 21, 2003 Share Posted February 21, 2003 FYI... on my NA 3L I'll be mostly running a 4.11 gear with my .87 overdrive 5th. The engine has a soft redline of 7' date='500 and was built as a torque motor so its horsepower and torque curves are very similar to a 300 hp turbo motor.[/quote'] i meant you wont be in gear long enough to boost... Quote Link to comment Share on other sites More sharing options...
Mike C Posted February 21, 2003 Share Posted February 21, 2003 That's a perfect illustaration why road race cars have close ratio transmissions, because of the effective widening of said ratios with the high number rear gear. It is very common for Trans Am racers to run 4.56 gears. And back to why the T5 is the best choice for a street car where good acceleration needs to be combined with reasonable highway rpm. I don't know if any of this is still related to the original thread, but good info nonetheless! For that matter, I don't know how common/uncommon the T5 is down under. I agree wholeheartedly with John, and if you have read my posts concerning the T56, you'll see that the MOST gear you can get is ALWAYS the best choice IMO. Top speed has never been a real interest of mine as there are really no places to test/achieve this without great risk to person/property that I have reasonable access to. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 21, 2003 Share Posted February 21, 2003 i meant you wont be in gear long enough to boost... Yeah, I guess a turbo would be a slightly different story if your turbo takes a bit to spool up. The old 934 single turbo Porsches ran a wide ratio 4 speed with various rear gears (from 5.88 to 3.9x) to suit the tracks they ran. The drivers used to left foot brake while keeping their foot in the throttle to keep the boost up. Better have damn good brakes. Quote Link to comment Share on other sites More sharing options...
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