miatapasta Posted December 12, 2016 Share Posted December 12, 2016 Hey, guys. I know that welding a differential is not a great thing to do to an axle that drives a car. Trust me, people weld and blow diffs on Miatas all the time, so I've seen the bad side effects. But I had an idea last night and I wanted your input on it. Let's say I do the switch mod that lets me lock the center diff on the 4EAT. This way I can manually control the 50/50 torque split. That's cool and all, but I still have the stock open diffs. So to add on to that idea, I also know that you can install a fuse to convert the car to FWD. My question/point of this thread is: If I welded the rear open diff and only used FWD on the street, with no power to the rear axles, would I still encounter the negative side effects of welded diffs (wheel hop, CV stress, etc?) I'm assuming yes, but wanted to make sure. In a perfect world, I would have two switches: one that shuts off power to the rear diff for normal street driving. This would save the rear welded diff strictly for off road use. I would also have another switch for the center diff, allowing the 50/50 torque split to be more effectively used in the rear. If I am way off, or this is just a crazy notion, feel free to let me know. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted December 12, 2016 Share Posted December 12, 2016 Yes, it would reduce the stress a little bit if they weren't loaded, but the hubs are still engaged to the axles full-time, so it would still be really hard on things on the street. Quote Link to comment Share on other sites More sharing options...
idosubaru Posted December 12, 2016 Share Posted December 12, 2016 It would remove the front to rear binding - so the driveshaft and transmission wouldn't see any issues. The binding would happen around turns and be relegated side to side in the rear - so the outer joints, inner joints, stubby shaft, ring and pinion. Just visualize a straight line across your axle, diff, axle and that's what will be binding - that entire rear driveline - the weak points would be the connecting joints i mentioned. So they would be cheap, easy to repair, and not leave you stranded like a transmission or ujoint possibly could. Just pop the pins out of the axle(s) and go on your way. Rear tires may wear faster due to the same thing. And I'm just guessing here but side to side binding is "easier" on the driveline than front to rear - less weight/HP from the engine and the binding may be lighter and not as bad as traditional binding. I'm thinking about pulling wagons and trailers (large toys, yard equipments) and such with solid axles - they're light and easily translate across surfaces compared to something driven/heavier/powered. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted December 12, 2016 Share Posted December 12, 2016 It would remove the front to rear binding - so the driveshaft and transmission wouldn't see any issues. The binding would happen around turns and be relegated side to side in the rear - so the outer joints, inner joints, stubby shaft, ring and pinion. Just visualize a straight line across your axle, diff, axle and that's what will be binding - that entire rear driveline - the weak points would be the connecting joints i mentioned. So they would be cheap, easy to repair, and not leave you stranded like a transmission or ujoint possibly could. Just pop the pins out of the axle(s) and go on your way. Rear tires may wear faster due to the same thing. And I'm just guessing here but side to side binding is "easier" on the driveline than front to rear - less weight/HP from the engine and the binding may be lighter and not as bad as traditional binding. I'm thinking about pulling wagons and trailers (large toys, yard equipments) and such with solid axles - they're light and easily translate across surfaces compared to something driven/heavier/powered. I disagree. The speed difference between the 2 wheels opposite is much more extreme than front-to-back. And with the Duty C engaged and a rear diff welded, the transmission, transfer clutches, and driveshaft are still not the weak link. It's the axle shafts. But being loaded with forward-drive torque, as well as the strain of different speeds on either side will put a bit more force on them then if they're just coasting, but not much. Also, I'm assuming your thinking of an EA82/XT6 with "pop the pins and go on your way". This is a 2000 Outback...axle failure isn't the end of the world, but it's much more difficult. As both ends must be present to keep the hub together and gear oil in the diff. And swapping out for a spare axle is not really an easy trail-side repair. Quote Link to comment Share on other sites More sharing options...
Scott in Bellingham Posted December 13, 2016 Share Posted December 13, 2016 I run a rear welded locked diff in many of my offroad cars, a couple keys to this is keep the rear light don't overload your trunk run good pressure in those tires and I don't drop a axle as its a hassle at the trailhead to reinstall and the smoother the tread the better, also its more squirrely in wet cornering Quote Link to comment Share on other sites More sharing options...
miatapasta Posted December 13, 2016 Author Share Posted December 13, 2016 I run a rear welded locked diff in many of my offroad cars, a couple keys to this is keep the rear light don't overload your trunk run good pressure in those tires and I don't drop a axle as its a hassle at the trailhead to reinstall and the smoother the tread the better, also its more squirrely in wet cornering How often does your car see the street? Mine is 90% street duty, but there is access to many trails by my house even if I decide to turn off the road on a whim. That being said, I think I've pretty much turned against the idea. Quote Link to comment Share on other sites More sharing options...
DaveT Posted December 13, 2016 Share Posted December 13, 2016 It doesn't sound like a good idea to run a welded diff for street use. Quote Link to comment Share on other sites More sharing options...
ferp420 Posted December 13, 2016 Share Posted December 13, 2016 I have a welded rear diff I swap in to my daily driver I can say it doesn't mater if the wheels are driven or not the binding is the same get your self some LSD and be happy lol much easier to deal with I like my limited slip but its wore out it ether locks solid or is open witch is OK the front to back binding I sent a big issue its only a problem like in a parking lot or some were slow tight turns are needed a locked rear and a locked center is bad on any hard surface even packed dirt all that sead your gonna brake stuff or were stuff out faster off road anyway so it really I sent a big deal its gonna start to feel like a truck anyway and feel loose an the road with enuff off road use unless your replacing parts regularly again get some LSD and be happy Quote Link to comment Share on other sites More sharing options...
miatapasta Posted December 13, 2016 Author Share Posted December 13, 2016 I've been doing a lot of research since posting, and it appears that really I'm stuck with the open diffs. Sure, one could weld it, but the point of this car is to be a daily driver with off road capabilities when needed. I could also go LSD, but they appear to have been all worn out at this point. If I'm wrong, let me know, but otherwise I've since abandoned the idea. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted December 13, 2016 Share Posted December 13, 2016 Subaru might sell you a new LSD diff, or the LSD internals but probably $$$saudiarabia$$$ Quote Link to comment Share on other sites More sharing options...
Numbchux Posted December 13, 2016 Share Posted December 13, 2016 (edited) Subaru might sell you a new LSD diff, or the LSD internals but probably $$$saudiarabia$$$ I was reading this thread and wondering just how expensive.... So I looked it up. Part #38434AA050, MSRP of $577.93, which is actually less than I thought. But.....discontinued. Looks like you could still get one straight from Japan through Amayama trading, but then it's more than $700 https://www.amayama.com/en/search?q=38434AA050 I'm sure you could get an aftermarket one, if you really wanted. Edited December 13, 2016 by Numbchux Quote Link to comment Share on other sites More sharing options...
idosubaru Posted December 13, 2016 Share Posted December 13, 2016 I disagree. The speed difference between the 2 wheels opposite is much more extreme than front-to-back. And with the Duty C engaged and a rear diff welded, the transmission, transfer clutches, and driveshaft are still not the weak link. It's the axle shafts. But being loaded with forward-drive torque, as well as the strain of different speeds on either side will put a bit more force on them then if they're just coasting, but not much. Also, I'm assuming your thinking of an EA82/XT6 with "pop the pins and go on your way". This is a 2000 Outback...axle failure isn't the end of the world, but it's much more difficult. As both ends must be present to keep the hub together and gear oil in the diff. And swapping out for a spare axle is not really an easy trail-side repair. I was totally thinking this was older generation. Indeed EJ would be more annoying. Goodness - the new VLSD unit is $700 and discountinued? wow. Quote Link to comment Share on other sites More sharing options...
miatapasta Posted December 13, 2016 Author Share Posted December 13, 2016 Yep, stuck with the opens I fear. I need to stop thinking this thing is a Jeep. Heh Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted December 13, 2016 Share Posted December 13, 2016 tochigi-fuji/GKN ?, rallispec or other for Torsen? investigate r-160 and r-180 diffs, maybe with swapped guts from another diff? 2005 STi ? GT-R rear diff???? there are some discussions about the above at NASIOC but they all sound expensive. Quote Link to comment Share on other sites More sharing options...
ferp420 Posted January 7, 2017 Share Posted January 7, 2017 I scored my lsd from the junk yard on half off day along with the rear disk set up for cheap cheap it helps to be patient and hunt around Quote Link to comment Share on other sites More sharing options...
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