pedrosixfour Posted August 18, 2009 Share Posted August 18, 2009 (edited) Hey folks, Still on the quest for lower gearing in my SZ-R I have now turned my attention to the gear ratios in the diff. While doing a bit of a search I came across this link: http://www.turbosupras.com/pages/pages/specifications/JZA80/jza80.htm In it the final drive ratio for the NA diff is given as 4.083 as is the value given in Homer's gear calculator yet when you divide the number of teeth on the crown wheel (47) by the number of teeth on the pinion (11) you get a ratio of 4.273. According to my calculations to get the ratio of 4.083 the crown wheel would need to have 49 teeth and the pinion would need to have 12 teeth. Has anyone else noticed this discrepancy or is it just me that was sad enough to be investigating NA diff ratios? Edited August 18, 2009 by pedrosixfour (see edit history) Quote Link to comment Share on other sites More sharing options...
Scooter Posted August 18, 2009 Share Posted August 18, 2009 Are you saying you have actually counted yours and got 47 and 11? Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted August 18, 2009 Author Share Posted August 18, 2009 Are you saying you have actually counted yours and got 47 and 11? No mate, the teeth count is on that link I posted. Quote Link to comment Share on other sites More sharing options...
Scooter Posted August 18, 2009 Share Posted August 18, 2009 Opps sorry i didn't look The 49/12 is whats quoted here so suspect the other link is incorrect? Quote Link to comment Share on other sites More sharing options...
Hermit Posted August 18, 2009 Share Posted August 18, 2009 The EPC says 49/12=4.083 for SZ-R up to May '96, and 49/13=3.769 after that. Lower gearing? So you want a 49/11? Not sure if there is one... some Chaser's had 41/10 and some 43/10, but I've no idea if they'd fit Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted August 18, 2009 Author Share Posted August 18, 2009 The EPC says 49/12=4.083 for SZ-R up to May '96, and 49/13=3.769 after that. Lower gearing? So you want a 49/11? Not sure if there is one... some Chaser's had 41/10 and some 43/10, but I've no idea if they'd fit Does anyone know if this 10 tooth pinion would be the correct size and pitch to mate to my NA 49 tooth crownwheel? Quote Link to comment Share on other sites More sharing options...
Hermit Posted August 18, 2009 Share Posted August 18, 2009 Does anyone know if this 10 tooth pinion would be the correct size and pitch to mate to my NA 49 tooth crownwheel? Very much doubt it. Do you really want a ratio that big? 4.9 Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted August 18, 2009 Author Share Posted August 18, 2009 Ha ha, it does sound a little extreme doesn't it? I would agree that 4.455 (49/11) would be a little less radical. Probably kinder to the diff too during down changes. But I did a check on the gear calculator (great tool, thanks Homer!) and I think I could live with it (4.9) around Mondello and as I said in a recent thread concerning a 6 speed conversion Mondello will be the car's main racing circuit. The car is a track use only toy by the way. Quote Link to comment Share on other sites More sharing options...
Hermit Posted August 18, 2009 Share Posted August 18, 2009 Just been reading that thread... I guess since an NA can't max out 5th anyway, maybe it's not as extreme as it first appears! But I don't know where you'd find one like that - maybe on a pickup or a truck?! The US 4.272 might be as far as you can easily go Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted August 19, 2009 Author Share Posted August 19, 2009 Just been reading that thread... I guess since an NA can't max out 5th anyway, maybe it's not as extreme as it first appears! But I don't know where you'd find one like that - maybe on a pickup or a truck?! The US 4.272 might be as far as you can easily go Cheers for the feedback Hermit. Would you or anyone else for that matter know whether any Mkiii pinion might be a suitable candidate for this application or was there a complete redesign for the Mkiv. Quote Link to comment Share on other sites More sharing options...
Hermit Posted August 19, 2009 Share Posted August 19, 2009 I dunno Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted August 20, 2009 Author Share Posted August 20, 2009 On mature reflection I think altering the diff ratio by too big a degree will just move the problem I have up a gear! If I view my W58 box as a 4 speed instead of a 5 speed with fifth gear being redundant for the purposes of racing at Mondello a 4.27:1 diff ratio would suffice. I also think I am running rear tyres that are slightly too wide for my rims, 255/40 instead of 245/40 on 9" rims, so when its time for a change I'll effectively gain a few percent on the final drive ratio there too. Plus it'll be a damn sight cheaper as I spoke to one of our Oz members yesterday who reckons grafting a JZX90 diff into place was the only method he could use which would then allow him to change the internals to a suitable ratio. Sod that! So with all that in mind could anyone shed any light on where I might find the toyota part no. for a 4.27 crown wheel and pinion gear set which appears to have been used in the US in certain supra models. And can anyone confirm that this item will fit directly into my NA A01B Torsen I LSD diff? Thank you very much you courteous, knowledgeable bunch you! Quote Link to comment Share on other sites More sharing options...
Hermit Posted August 20, 2009 Share Posted August 20, 2009 Well it would move it up a gear, maybe, but you might be more in the power band? Anyway, that's the important thing - get the gears closer so you've got a bit more freedom in gear choice, and it won't hurt your time as much when you stay in the higher gear round that corner. Part number here, seems they come as a set... I've no idea about compatibility, but I can't see any obvious reason why not. As far as I can tell from the EPC, the same gears are used on the open and torsen diffs. I have heard of a similar swap being done to Soarer diff (it might even have been a Supra NA diff being fitted to a Soarer, since they're compatible). So... hopeful, but I can't confirm it. Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted August 20, 2009 Author Share Posted August 20, 2009 Hermit, you sir are a gentleman, provided of course you are male. If you are female, fancy a drink?? Quote Link to comment Share on other sites More sharing options...
Hermit Posted August 20, 2009 Share Posted August 20, 2009 Lol... you're welcome, but leave your coat where it is, you haven't pulled! Jon Quote Link to comment Share on other sites More sharing options...
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