Hutch Posted August 25, 2016 Report Share Posted August 25, 2016 Wondering if someone can answer this question, I've read some posts saying 4x4 leaf springs swap in to rwd trucks and effectively lower it an inch and change, and I've also read that on some trucks (Canadian?) The 4x4 spring eyes don't line up at all and displace the axle in the wheel well if you can get it to fit. Anyone with a Canadian rwd 720 swap in canadian 4x4 leaf springs and have it work? 1 Quote Link to comment
datzenmike Posted August 26, 2016 Report Share Posted August 26, 2016 There's no difference in N American 720 truck springs, other than number of leaves and the spring rate. The 520/521/620 and 720 leaf springs are all 1,200mm long from eyelet to eyelet and interchange. The 720 4x4 spring lays flatter with much less arch in it and it is much stiffer that any 2wd springs. 1 Quote Link to comment
Hutch Posted August 26, 2016 Author Report Share Posted August 26, 2016 This is the thread that's leading to my confusion: http://www.infamousnissan.com/forum/showthread.php?t=9616 Now I know that they're referring to D21s, but are the leaf springs not the same through that generation as well? Also, with the added leaf I've also read that the canadian leaf packs have a higher spring rate and are stiffer. Would the jump to the 4x4 leafs offer a noticeable difference? I'd like to stiffen up the rear as much as possible due to the tight fender clearance I'm running right now. I like the height but anything to stiffen it up would help. 1 Quote Link to comment
datzenmike Posted August 27, 2016 Report Share Posted August 27, 2016 You ask about 720 leaf springs.... Wondering if someone can answer this question,I've read some posts saying 4x4 leaf springs swap in to rwd trucks and effectively lower it an inch and change, and I've also read that on some trucks (Canadian?) The 4x4 spring eyes don't line up at all and displace the axle in the wheel well if you can get it to fit.Anyone with a Canadian rwd 720 swap in canadian 4x4 leaf springs and have it work? This is the thread that's leading to my confusion: http://www.infamousnissan.com/forum/showthread.php?t=9616 Now I know that they're referring to D21s, but are the leaf springs not the same through that generation as well? Now you mention the D21 Hardbody? The D21 information on the website has no bearing on your 720 whatever. All I can say with assurance is that the D21 leaf springs are the same length 1,200mm and the same width 60mm as the 720. Where the center mounting bolt is or if they will properly swap to a 720 and center the axle in the body opening is unknown to me. Also, with the added leaf I've also read that the canadian leaf packs have a higher spring rate and are stiffer. Would the jump to the 4x4 leafs offer a noticeable difference? I'd like to stiffen up the rear as much as possible due to the tight fender clearance I'm running right now. I like the height but anything to stiffen it up would help. Are we talking about the 720 springs??? Per the '84 720 FSM...The US 2wd spring constant (stiffness) is 310 lb/in.The US optional 2wd spring constant is 442 lb/in and is the same as the regular Canadian 2wd spring constant. In other words Canadian trucks all got optional US spring.The Canadian 2wd optional spring is a softer spring and the same as the standard US 2wd spring. Why they are switched makes no sense to me. ALL Heavy Duty and Cab/Chassis springs are 649 lb/in All 4x4 springs are 442 lb/in spring rate. Identical to the US optional and the Canadian standard spring. The only difference is the free camber. The 'Free Camber' is measured on an unloaded spring by drawing a string from front to back through the center line on the mounting bolt eyelets and measuring down to the center top of the leaf pack. Two wd spring 'free camber' are as follows.... US 2wd standard and Canadian optional...... 6.34" US optional and Canadian standard.............. 5.20" Heavy Duty and Cab/Chassis....................... 4.51" 4X4................................................................. 3.68" Just because I have my books out. Here are the D21 leaf spring (spring constant) and the (free camber) specs, per the '86 FSM..... US 2wd................................... 331 lb/in........... 6.89" Canadian 2wd........................ 436 lb/in............ 6.65" ALL HD and Cab/Chassis...... 655 lb/in........... 5.47" All 4X4..................................... 515 lb/in........... 4.09" 1 Quote Link to comment
Hutch Posted August 27, 2016 Author Report Share Posted August 27, 2016 Now you mention the D21 Hardbody? The D21 information on the website has no bearing on your 720 whatever. All I can say with assurance is that the D21 leaf springs are the same length 1,200mm and the same width 60mm as the 720. Where the center mounting bolt is or if they will properly swap to a 720 and center the axle in the body opening is unknown to me. Sorry for some reason I was thinking the later generation springs were interchangeable. Thanks for clearing that up! 1 Quote Link to comment
datzenmike Posted August 27, 2016 Report Share Posted August 27, 2016 Hey, they may be the same. I have no idea about them only the earlier trucks. Get a tape measure and take a walk through a 'yard'. Measure the rear eyelet center line to the center of the axle and compare to your 720. Then let me know so I have this for the next guy who asks. 1 Quote Link to comment
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