Doobie Posted July 24, 2021 Report Share Posted July 24, 2021 Just wondering if anyone knows how many leafs are in a stock set of springs , not positive but I think the previous owner of my 620 may have added a helper leaf Quote Link to comment
datzenmike Posted July 24, 2021 Report Share Posted July 24, 2021 They started very stiff in '73 and then lightened around '77 and up. There was an optional 'camper' spring which was basically the same as the original '73-'76. I have a 73 FSM and it says 5 leaves of various lengths and thicknesses. My '78 FSM says only 3. What are your plans? lowering? Quote Link to comment
Doobie Posted July 25, 2021 Author Report Share Posted July 25, 2021 Yes planning on lowering it , my truck just seems to sit a little high Quote Link to comment
datzenmike Posted July 25, 2021 Report Share Posted July 25, 2021 Use lowering blocks and longer U bolts. Never remove a leaf to lower. The last thing you want is to be closer to the pavement and the springs are softer and travel farther on bumps. If anything you want them even stiffer to prevent bottoming out. These are 3" but you can get less... https://www.amazon.ca/Belltech-6100-Lowering-Block-Kit/dp/B000CIMEPE/ref=asc_df_B000CIMEPE/?tag=googleshopc0c-20&linkCode=df0&hvadid=292992180896&hvpos=&hvnetw=g&hvrand=15257457437751320046&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001614&hvtargid=pla-521790039529&psc=1 Quote Link to comment
Doobie Posted July 25, 2021 Author Report Share Posted July 25, 2021 I have three inch blocks and u bolts , I’m asking because I think the previous owner might have added a leaf to raise the rear to fit the massive tires he had on it Quote Link to comment
datzenmike Posted July 25, 2021 Report Share Posted July 25, 2021 5 or 3 is my guess so if you have 6 or 4 then maybe one added. Quote Link to comment
620slodat Posted July 25, 2021 Report Share Posted July 25, 2021 I have a 1973 Datsun 620 available to me to look at, which I did. I know for a fact that it hasn't had anything changed on the rear suspension since my dad bought it brand new in 1973. It has 5 leaves total. The top three are standard thickness, the fourth is an overload leaf about 1/2": thick and about 3/4 length (or slightly less) of the first leaf, and leaf #5 is back to standard thickness and about 1/4 the length of the top leaf. Don Quote Link to comment
Doobie Posted July 25, 2021 Author Report Share Posted July 25, 2021 Thank you!! Quote Link to comment
datzenmike Posted July 25, 2021 Report Share Posted July 25, 2021 12 hours ago, 620slodat said: I have a 1973 Datsun 620 available to me to look at, which I did. I know for a fact that it hasn't had anything changed on the rear suspension since my dad bought it brand new in 1973. It has 5 leaves total. The top three are standard thickness, the fourth is an overload leaf about 1/2": thick and about 3/4 length (or slightly less) of the first leaf, and leaf #5 is back to standard thickness and about 1/4 the length of the top leaf. Don 620slowdat: The spring rate is progressive becoming stiffer and the spring is compressed. The '73 5 leaf spring rate was 145 to 560 pounds/inch. The later springs that were 3 leaves were 106 to 308 lb./in. A lot softer. Quote Link to comment
620slodat Posted July 26, 2021 Report Share Posted July 26, 2021 DM, just out of curiosity, do you know the rear spring rate for a 1982 720? I had a 1982 720 diesel frame given to me by wayno, and I am curious to know what it might have. I don't have an OEM book for it. Also, I looked on-line and haven't found it yet. I will continue looking though unless you have that information. Don Quote Link to comment
datzenmike Posted July 26, 2021 Report Share Posted July 26, 2021 I only have the '84 FSM. The US standard spring is 109-310 lb/in. The optional spring, which is the same as the 4x4 spring and is the standard spring for Canada is 138-442 lb./in. and the optional Canadian spring is the same as the US standard. The Cab/Chassis spring is 166-649 lb./in. Quote Link to comment
620slodat Posted July 27, 2021 Report Share Posted July 27, 2021 Thank you DM! You may not have the 1982 FSM, but 1984 is pretty close. Close enough for me to be able to know that the spring rate should be a lot less than the 1973 spring. The average 1984 spring rate is 210 lbs (310-109, divide by 2+109=209.5). The average 1973 spring rate is 352.5 lbs (same formula as used previously). Over 140 lbs difference between the two makes for a big difference. Don Quote Link to comment
datzenmike Posted July 27, 2021 Report Share Posted July 27, 2021 Not sure if that's a good ruler. At rest it takes 210 pounds to compress one inch but as it's being compressed the rate is also going up as more leaves come under compression. Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.