elcamino/wheelhorse 9,297 #1 Posted September 28, 2022 I can't find and specs on torque requirements for 4 bolts that attached trans to frame. Anybody got an idea ? 1 Share this post Link to post Share on other sites
ebinmaine 67,358 #2 Posted September 28, 2022 I believe those are a standard 3/8 16 thread? It would depend on the bolt you're using. Grade 5 would be about 30, 35 FOOT pounds. Grade 8 of course would be a little higher. 2 Share this post Link to post Share on other sites
ri702bill 8,298 #3 Posted September 28, 2022 Be careful - the Unidrive is cast iron and you need 2x thread size, so 3/4" engagement so as not to strip them out when applying the grunt pounds...... 5 Share this post Link to post Share on other sites
Achto 27,519 #4 Posted September 28, 2022 (edited) If you use Loctite, use the oiled torque spec. Loctite will lubricate until it dries. Edited September 28, 2022 by Achto 2 3 1 Share this post Link to post Share on other sites
ebinmaine 67,358 #5 Posted September 28, 2022 50 minutes ago, ri702bill said: Be careful - the Unidrive is cast iron and you need 2x thread size, so 3/4" engagement so as not to strip them out when applying the grunt pounds...... I don't think I've ever measured the thread depth on those transmissions. Do we suppose there is ¾ thread depth in there on all four holes? 1 Share this post Link to post Share on other sites
Pullstart 62,817 #6 Posted September 28, 2022 Run ‘em in until they snap, then back ‘em off 1/4 turn! 6 Share this post Link to post Share on other sites
Pullstart 62,817 #7 Posted September 28, 2022 5 minutes ago, ebinmaine said: I don't think I've ever measured the thread depth on those transmissions. Do we suppose there is ¾ thread depth in there on all four holes? I do believe there is. That’s the machinery standard for cast iron threads… two times the diameter. 3 1 Share this post Link to post Share on other sites
ri702bill 8,298 #8 Posted September 28, 2022 (edited) 3 hours ago, ebinmaine said: Do we suppose there is ¾ thread depth in there on all four holes? Yup, and for once, Kevin is absolutely correct regarding the thread engagement in cast iron... Edited September 28, 2022 by ri702bill 4 Share this post Link to post Share on other sites
ri702bill 8,298 #9 Posted September 28, 2022 30 minutes ago, Pullstart said: Run ‘em in until they snap, then back ‘em off 1/4 turn! Farmer !!! 3 Share this post Link to post Share on other sites
Pullstart 62,817 #10 Posted September 28, 2022 13 minutes ago, ri702bill said: Yup, and for once, Kevin is absolutely correct redarding the thread engagement in cast iron... For once? Ouch! I’m putting this in my bumps and bruises catalog! 3 Share this post Link to post Share on other sites
ri702bill 8,298 #11 Posted September 28, 2022 59 minutes ago, Achto said: If you use Loctite, use the oiled torque spec. Loctite will lubricate until it dries. Looking at the torque spec for the 1-1/2" being up over 3500 ft lbs reminds me of an assembly job I did once - assisting to torque 24 bonnet studs with machined nuts on a prototype nuclear powerplant water valve. The studs were 3X taller than the height of the nut. It took 3 of us - two assemblers and a certified inspector two and a half DAYS to do this - the bonnet was assembled first with the nuts hand tight and then torqued to 50 ft lbs, then 100 by hand as the inspector verified the criss-crossed torque sequence. Then it was time for the big toys - a hydraulic device that attached to the stud above the nut and pressed on the bonnet surface with a shell that looked like an oxygen sensor cut socket - pressure was applied to stretch the stud, and you tightened the nut about one flat (1/6th of a turn), relax the pressure, remove the tool, onto the next stud. All this in 100 ft lb increments x 24 fasteners, up to the 4000 ft lb torque spec. That is why it took so long.... 2 2 Share this post Link to post Share on other sites
ri702bill 8,298 #12 Posted September 28, 2022 4 minutes ago, Pullstart said: For once? Ouch! I’m putting this in my bumps and bruises catalog! The key word is "absolutely" - meant as a compliment.... 3 Share this post Link to post Share on other sites
squonk 41,043 #13 Posted September 28, 2022 2 hours ago, ri702bill said: when applying the grunt pounds...... With Waldo were talking grunt inches! 2 Share this post Link to post Share on other sites
Ed Kennell 38,063 #14 Posted September 28, 2022 (edited) At first, it would seem logical to simply increase the length of thread engagement by as much as required to overcome the limitations of engaging with a material of limited proof strength. In reality, however, only the first few threads of a threaded connection are actually involved in sharing the fastener clamping force. This is due to thread form error and slight differences in thread size and pitch that result in an inconsistent make-up between the male and female threads. A common rule-of-thumb is to provide a minimum length of thread engagement equal to the (major) diameter of the fastener. A more conservative rule-of-thumb is to use a thread engagement length of 1-1/2 times diameter.in general a course threaded screw grade 2 should be at least 1 dia threaded depth in cast iron. a grade 5 screw should be 1.5 dia depth and a grade 8 screw should be 2 dia threaded depth into cast iron. for screw strength to match cast iron. Edited September 28, 2022 by Ed Kennell 2 1 1 Share this post Link to post Share on other sites
ri702bill 8,298 #15 Posted September 28, 2022 24 minutes ago, Ed Kennell said: rule-of-thumb No there's a phrase with a dark, twisted origin..... 2 Share this post Link to post Share on other sites
Wild Bill 633 845 #16 Posted September 28, 2022 (edited) Because these bolts are known to loosen up, on my build I am going to red loctite alloy steel set screws into the transaxle and use center-lock distorted-thread grade 8 flange nuts. Edited September 29, 2022 by Wild Bill 633 3 1 Share this post Link to post Share on other sites
Pullstart 62,817 #17 Posted September 28, 2022 1 hour ago, ri702bill said: The key word is "absolutely" - meant as a compliment.... The key words “for once” are the bruised portion I’m referring to 1 Share this post Link to post Share on other sites
Pullstart 62,817 #18 Posted September 28, 2022 25 minutes ago, Wild Bill 633 said: Because these bolts are known to loosen up, on my build I am going to red locktite alloy steel set screws into the transaxle and use center-lock distorted-thread grade 8 flange nuts. That’s pretty genius. Will the top cross-shaft in the transmission (for the clutch idler pulley) become a nuisance? 2 Share this post Link to post Share on other sites
ri702bill 8,298 #19 Posted September 28, 2022 41 minutes ago, Pullstart said: The key words “for once” are the bruised portion I’m referring to Perhaps "this time" would have been a softer choice... 41 minutes ago, Pullstart said: Will the top cross-shaft in the transmission (for the clutch idler pulley) become a nuisance? Depends on the length of the setscrews... uppers only need be be a tad longer than the seated nut. Kind of like the old hot rod days using alignment studs in the bell housing to help guide the 4 speed thru the throwout bearing and into the clutch disc.... get 2 bolts started, unscrew the studs, in goes the last 2 bolts. 1 Share this post Link to post Share on other sites
