minitrucker80 Posted March 3, 2013 Report Share Posted March 3, 2013 Okay I have a 1985 720 2.4 5 speed...I put a 1971 521 rear end in my truck cuz I needed a shorter rear end....Everything works great...But now my truck in 5th gear at 65 is running high high rpms...Will my gears out of my 720 rear end bolt-in the 521 rear end or do i have to find 521 gears...any help or link to 521 higher gears for sale if 720 gears wont work... Quote Link to comment
Jayden71 Posted March 3, 2013 Report Share Posted March 3, 2013 What year of 521. Most of them had 4.37s. If it had a J engine it had 4.88s Duh never mind just reread the post. Yeah you more than likely put 437s in your 720 Quote Link to comment
wayno Posted March 3, 2013 Report Share Posted March 3, 2013 Yes your 720 gearset/pumpkin will bolt into the 521 housing as long as it is a H190 720 rearend. Quote Link to comment
Phixius Posted March 3, 2013 Report Share Posted March 3, 2013 Okay I have a 1985 720 2.4 5 speed...I put a 1971 521 rear end in my truck cuz I needed a shorter rear end....Everything works great...But now my truck in 5th gear at 65 is running high high rpms...Will my gears out of my 720 rear end bolt-in the 521 rear end or do i have to find 521 gears...any help or link to 521 higher gears for sale if 720 gears wont work... I got a little confused reading that.. so you put the whole 521 rear end in for a narrower track width? to fit wide rims and/or low offset? All 2wd 720s with 4cyl have h190s. and, yes they are both H190s and the pumpkins/center sections/gear sets interchange. the 521s have a 4.375 with a L motor and 4.875 with a J motor. I think 720s came with 3.364, 3.54, 3.70, 3.889, 4.11 and 4.375 . you can check your tag on your 720 to see what one yours came with. It will read HF37 or HF38 ect... I put 3.889 in my 521 just swapping the gear set... Quote Link to comment
minitrucker80 Posted April 9, 2013 Author Report Share Posted April 9, 2013 thanks everyone for the info....im going to just take the gear set out of my 720 rearend and swap to the 521....one more question does the hardbody also have the h190 rearend Quote Link to comment
bryant2482 Posted April 29, 2013 Report Share Posted April 29, 2013 yes. i just pulled out a 3.54 out of a 1990 hardbody today Quote Link to comment
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