r600 Posted July 18, 2007 Share Posted July 18, 2007 can anyone help?i am doing rear trunnion bush's 34,000 backend its got the red bushes when i did them up the lower trunnion half cap broke.i have been told the red bushs are no good to hard?help Quote Link to comment Share on other sites More sharing options...
Rob Posted July 18, 2007 Share Posted July 18, 2007 can anyone help?i am doing rear trunnion bush's 34,000 backend its got the red bushes when i did them up the lower trunnion half cap broke.i have been told the red bushs are no good to hard?helpI've seen several of the polyurethane bushings break the lower caps upon tightening up the bolts and nuts. This is usually the result when an impact wrench is set on high torque, and the fasteners are not drawn down evenly. I usually tighten in a four step torque process using an "X" pattern. Ultimately, these fasteners need about 1250-1400 ft. lbs. applied. It is easy to get "over zealous" to get the job done quickly. Also, be sure to lube up the exterior, and interior of the bushings before installation. This will allow them to move a bit as they compress.Good Luck.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
Lmackattack Posted July 18, 2007 Share Posted July 18, 2007 Rob i was told not to grease up the bushings as it helps push them out faster? i wonder what others think?My opinion is that they should have some lube to help them wiggle on tight turns but thats just my .02As for the caps i have seen them snap as well (on my truck) i just bought new ones as mine were worn from old age Quote Link to comment Share on other sites More sharing options...
greg Posted July 18, 2007 Share Posted July 18, 2007 I lubed mine up with soapy water, then I put a block between axel tube and frame and put a jack under the cap to compresss the bushings up then tightened up the bolts. Quote Link to comment Share on other sites More sharing options...
b61fred Posted July 18, 2007 Share Posted July 18, 2007 I have read the proceedure to installed these bushings in the manual for my truck. It said to use dishwashing soap to lube the bushings, I would say greese or oil would have softened to natural rubber ones used in the old days, the soap would just dry up I guess.Fred Quote 15 gears...no waiting! Link to comment Share on other sites More sharing options...
Rob Posted July 19, 2007 Share Posted July 19, 2007 Rob i was told not to grease up the bushings as it helps push them out faster? i wonder what others think?My opinion is that they should have some lube to help them wiggle on tight turns but thats just my .02As for the caps i have seen them snap as well (on my truck) i just bought new ones as mine were worn from old ageWhile true of natural rubber, or to an extent, Neoprene, oil/grease will soften and attack rubber where polyurethane, (of which the conversation speaks of) is impervious to attack from petroleum products.I actually use silicone grease, (dielectric compound such as used on spark plug boots) for lubrication of urethane parts. It keeps the speaking to a minimum long term.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment Share on other sites More sharing options...
r600 Posted July 19, 2007 Author Share Posted July 19, 2007 While true of natural rubber, or to an extent, Neoprene, oil/grease will soften and attack rubber where polyurethane, (of which the conversation speaks of) is impervious to attack from petroleum products.I actually use silicone grease, (dielectric compound such as used on spark plug boots) for lubrication of urethane parts. It keeps the speaking to a minimum long term.Robthanks for all your comments.i have got new trunnion caps on the way and think i will change the red bush's to rubber. my parts man has told me the bush's only come in 8 1/4 or 6 5/8 but my red bush's are 7 1/2???can anyone help with the right bush maybe a part number . thanks again Quote Link to comment Share on other sites More sharing options...
Camelback Posted November 16, 2007 Share Posted November 16, 2007 Heres my 2 cents for what its worth. I have no ideal about the part numbers or the size they have always worked when i bought them and never really checked the size of them. But i do know that the Red bushings will outlast the rubber bushings by a long shot. The rubber ones always seemed to wear too quick for me. I eventually changed the stands and springs over too 44,000 with the brass bushings on a 74 R-600 that orignally had 38,000 I got alot more service out of it after the swap but it really does depend on how your using the truck before you convert it over to the brass bushing type Quote Link to comment Share on other sites More sharing options...
fjh Posted November 23, 2007 Share Posted November 23, 2007 thanks for all your comments.i have got new trunnion caps on the way and think i will change the red bush's to rubber. my parts man has told me the bush's only come in 8 1/4 or 6 5/8 but my red bush's are 7 1/2???can anyone help with the right bush maybe a part number . thanks againThe secret to making the brass trunion last is to jack the truck off the ground (all the weight off the wheels) let em hang! then grease em!Grease will always take the path of least resistance and that being the up side of the trunion when the weight is on the wheels ,the bottom side while hangingthis way your putting the grease where it needs to be!on the bottom. Quote Link to comment Share on other sites More sharing options...
Camelback Posted November 23, 2007 Share Posted November 23, 2007 That is the best way to do them fjh except most ppl don't go to the trouble of it and i am guilty of that myself. Grease is the key to the bronze bushings. they actually need a grease fitting on the bottom side also. Even if they are not jacked up its best to at least hit them once a day with a squirt of grease. Quote Link to comment Share on other sites More sharing options...
terry Posted November 24, 2007 Share Posted November 24, 2007 thanks for all your comments.i have got new trunnion caps on the way and think i will change the red bush's to rubber. my parts man has told me the bush's only come in 8 1/4 or 6 5/8 but my red bush's are 7 1/2???can anyone help with the right bush maybe a part number . thanks again Just take the 8 1/4 long one and cut it off to the right lenght. terry Quote Link to comment Share on other sites More sharing options...
Mackpro Posted November 26, 2007 Share Posted November 26, 2007 Back in the late 80's while at the Mack school they told us to use " edible beef tallo" (exact words) to lube the rubber bushings. When I asked the instructor what this was he said cow fat. While writing this reply I looked in my old Mack service manual for a MB685 printed in 1973 says to " coat rubber insulators with liquidsoap. do not use grease or oil." 1 Quote Link to comment Share on other sites More sharing options...
Art_H Posted May 26, 2014 Share Posted May 26, 2014 Old thread I know...But I'm replacing y worn rubber trunnions to urethane. My thoughts are that the grease would help the urethane move on the trunnion shaft. I understand the theory behind protecting the rubber style from harm, but clearly the urethane is impervious grease. Thoughts?? I did manage to snag some 30wt non-detergent oil...but I don't tyhink I'll use that now. My Mack TS442 books spec 'edible mutton tallow or 20 Wt non-detergent'.'Glad I saw this thread before I started torqing the u-bolts...Thanks,Artt Quote Link to comment Share on other sites More sharing options...
br549 Posted May 27, 2014 Share Posted May 27, 2014 We changed several over to the 1 piece saddle with the pressed in steel and rubber bushing. They hold up a lot longer,sorry dont have part # but any mack dealer should have it. Quote Link to comment Share on other sites More sharing options...
2stacksuperdog Posted May 27, 2014 Share Posted May 27, 2014 We converted to the steel bonded bushing when we replaced the spring on our 84 R. Gonna do it to the other side when necessary. A lot better. Quote Matt Link to comment Share on other sites More sharing options...
Art_H Posted May 27, 2014 Share Posted May 27, 2014 No spring change required? Just the 1 piece bushing is pressed onto the trunnion? That piece replaces the 2 piece clamshell system? Thanks.Art Quote Link to comment Share on other sites More sharing options...
blackdog2 Posted May 27, 2014 Share Posted May 27, 2014 Yup it is one piece cast steel spring saddle also you can put the little steel blocks in the spring caps they help a lot.And on the two piece saddle small rubber you could 1/2# shims. Quote Ed Link to comment Share on other sites More sharing options...
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