davek Posted September 19, 2015 Share Posted September 19, 2015 I recently installed an R200 with a 3.54 ratio gears in my 240Z. Ratio tested by counting drive shaft rotations per wheel rotation. It has the black plastic gear in the transmission but the speedo is reading faster than the car is moving. I will drive with a GPS later this week to get an accurate speed variation. The tranny is the BW T5. Both tranny and diff came out of a doner 1983 Turbo car. Anyone have a known solution. Everything I have read says the black gear in the one needed. The black gear was in the tranny unmolested when I bought it. Stock 1973 240z speedometer. Dave Quote Link to comment Share on other sites More sharing options...
RB26powered74zcar Posted September 19, 2015 Share Posted September 19, 2015 Apparently your diff is not a 3:54. If you want 100% conformation, you'll need to remove the rear cover and look at the numbers stamped on the ring gear . Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 19, 2015 Share Posted September 19, 2015 Tire size matters. My gears work as expected to give an almost perect speedometer reading. 205-70-14. 25.3" diameter by calculator. Smaller would read faster. I've had a 3.54 and a 3.9 in it and the right gear gives the right speed. http://tire-size-conversion.com/tire-size-calculator/ Does the BW use the same colors and numbers as the Nissan 71B and C transmissions? Maybe that's the problem. Quote Link to comment Share on other sites More sharing options...
Andreas Posted September 20, 2015 Share Posted September 20, 2015 If it was fine before maybe your diff got another gearing, pop cover and check. Or if your speedo shows to high(the same amount all the time) speed throw out the scale, you could just pop the speedo needle and put it back in pointing a bit lower. Iv done that many times when converting mph gauges to km/h gauges. Just give it a test drive before you put it back together. Quote Link to comment Share on other sites More sharing options...
davek Posted September 20, 2015 Author Share Posted September 20, 2015 Wow, thanks for the quick replys. It does have 3.54 gears easily checked by counting drive shaft rotations to wheel rotation. I did not drive the car before the tranny & diff swap I did with the donor car. My tires are 195/70-14 very similar to stock 240Z tires so this is not the problem either. Andreas I will check with a GPS are stated later this week if it is indeed a constant speed variation I will move the needle as you suggest. I hope it is that simple. I'll reply Friday or sooner after my drive with GPS. Waiting on return of my fuel injectors. That's a whole other discussion. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted September 21, 2015 Share Posted September 21, 2015 Use wax pencil or sharpie to put a discrete mark the speedometer face at each of the important speeds in your life. Or just drive with traffic. Quote Link to comment Share on other sites More sharing options...
davek Posted October 2, 2015 Author Share Posted October 2, 2015 Speedo is off about 15 mph highway speed. Reading faster than actual. Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 2, 2015 Share Posted October 2, 2015 That's a lot. If you can't find the info on BW gear colors you could just bite the bullet and get one with more teeth and swap it in. See what happens. You'll find the closest match eventually. Quote Link to comment Share on other sites More sharing options...
Andreas Posted October 2, 2015 Share Posted October 2, 2015 Does it show about 15 mph to high throw out the scale? Quote Link to comment Share on other sites More sharing options...
davek Posted October 3, 2015 Author Share Posted October 3, 2015 I'm leaning toward a blue 18 tooth gear and see what happens. another $30 spent. I will try the rolling car/tire again to check diff gearing. 3.54 to 3.70 is pretty significant. Yes I know both wheel need to be on the ground or tuning the same. Quote Link to comment Share on other sites More sharing options...
davek Posted October 4, 2015 Author Share Posted October 4, 2015 Can I assume the standard Nissan tranny gears will fit the BW T5? Anybody have actual experience. Cheers Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 4, 2015 Share Posted October 4, 2015 The part for the Z31 BW T5 (FS5R90A) has Z31 in the part number. Might mean something. The 280ZX T5 is also the FS5R90A. Probably just a different bell housing. Number of teeth is shown in the part description. Quote Link to comment Share on other sites More sharing options...
davek Posted November 20, 2017 Author Share Posted November 20, 2017 I put a white gear in the tranny and gained a little ground. Reads 10-11 mph fast now. Sorry I should have posted this a long time ago. Been driving with GPS for a year or better. Time to start looking for a solution. I'm thinking swapping in the guts of an electric speedo and use the original face. Thanks what I did for my tach. I'm running. MS3X Quote Link to comment Share on other sites More sharing options...
ZHoob2004 Posted November 20, 2017 Share Posted November 20, 2017 Not sure if it's the same as your problem or not, but my speedo seems to be fairly accurate up until I get up to highway speed (about 55) at which point the scaling seems to change and it jumps up 10-30mph faster than I'm going, essentially becoming useless. My intention is to take the speedo out and give it a thorough cleaning, but it hasn't happened yet so I don't know if that's the problem or not (for the record, I'm running a 3.7 rear with the cog for a 3.54) Quote Link to comment Share on other sites More sharing options...
Sandy455 Posted November 22, 2017 Share Posted November 22, 2017 I got a phone windshield mount and a GPS speedo app. Quote Link to comment Share on other sites More sharing options...
AlbatrossCafe Posted November 22, 2017 Share Posted November 22, 2017 Phone seems to be easiest I wish I could just add an correction-adjuster inline in the wire going to the speedo like you can on newer cars. Quote Link to comment Share on other sites More sharing options...
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