dragonwagon

I got back to the shop today the rear pinion is throughing 80w90 every where . Quick check of it , pinion nut is loose , its keyed I see . No up and down movement but theres a lot of rotational slop in the gears . Iv worked on rear diffs but not on trucks this large and that Mack rear looks like a different animal .

Im leaving on vacation late tonight so ill deal with it Monday . What can you guys tell me about this rear diff ?

They known for pinion problems ? bearing issues ? Id suspect a bearing issue given the high amount of rotational slop there is , something has the gears separated way to much .

Any one has an exploded view of this rear axle would be very helpful too .

havnt been on here in some time , wife of 35 years decided to file divorce .

Any advice would be helpful guys .

Thanks Rob , yes i would change the clutch while i had it down . Just had no idea if id find something standard or some odd " mack only " clutch set up . A 9 speed is smaller/lighter then the Mack trans . Man that thing is HUGE . I didnt know who made the multi speed rear under a Mack , i just new they had them .

I think a 9 speed would really help that little 237 Mack motor pull the large loads .

drove a number of 2 speed elec shift rears , other then a motor burning out now and then they werent an issue . Never used the Mack multi speed though . Thanks for the input .

Next question then , does the Mack use standard 10 spline clutch , in other words can i drop a 9 speed out of some other truck in there ? Would have to alter the drive shaft but thats not a big deal . This is a working truck and needs help . Not interested in repowering the truck . 9 speed would be smaller and lighter then the current trans .

My R model is lacking in gears , 5 speed trans . I know Mack made multi speed rear ends . The rear end has side plates that remove , did the multi speed units just bolt on or like GM and Ford was it a different housing for a multi speed rear ?

Worse case i may need to find a 2 speed out of a LN800 Ford or something of that sort . Not much aroun here for Mack parts to find . If the multi speed was a bolt on then maybe i can find one and have it shipped .

really ! theres no way id run those miles on 1 oil change .

Id rather not have that volume of oil , extended service is ok for long haul trucks , this one makes to many cold starts which contaminates fuel quicker . Any idea how many miles to an oil change there claim ?

Yes this has the huge fuel filter and large water filter .

Dont buy a deisel , currently there is NO good eisel motors out there to buy unless you go pre 07 . Duramax id stay away from , allison trans is a watered down allison , nothing like you think of in a medium duty truck . I do towing for a living , seems duramax is hit and miss , one guy has no issue the next guy nothing but issues .

Ford , well prior to the 6.0L they had a good diesel truck , 6.0 has been bad news the newer 6.4 is it ? not any better . All are having issues sorting out these new filttration systems they had to put on . Urea burners now . Id go to a GM 8.1 L if your towing or a Ford V10

Starting in 2012 Ford is putting the v 10 back into the F 650 models even due to sales on the diesel motor . Do some math regarding gas v's diesel power . Giving the cost difference at purchase , oil change and fuel cost theres no value in a diesel pickup .

Thanks dave , guess ill ad the oil back up to the mark then . This is the 3 filter motor so that puts it just over 14 gallon . Ya that much oil is a bugger plus three filters were 46 something .

78 Mack with a 675 in it . I went to change the oil for the first time today . Stick said it was full but not over full when i started . Pulled 14 gallons of oil out of the pan . Taken a close look at the stick it appears to be altered . probable from a different engine , cut off and remarked id guess .

Any one know what the correct volume of oil would be with a filter change ? 3 filters on it . Engine that size is typically only 7 to 9 gallon on a more modern truck .

Mack dealer said he would try to find me an answer but it may be a few days . Id like to get this corrected asap .

Any trans with more gears would be good , 8LL i think would be a great trans in there . None are a cheap option unless we were to puke a trans or atleast a clutch where you had to pull the trans to start with . Just to swap it out will cost me trans and labor . Cant do that type of wrenching any longer . Age sucks .

78 mack , 235 hp with a 5 speed , man i keep thinking i need to put a 2 speed rear end in it . The step from 4th to 5th gear is just to much . 2 speed rear would really help .

Yep looks like that , I talked with a garbage truck mechanic today , said you need to remove the water filter and the 4 bolt cap there to get to it . Rather hidden .

thanks .

Ok my second post and i look like a dummy . Been around engines for ever , Where in heck is the thermostat located on this 675 ? Top hose connects to the the block , dont look like any thermostat could be in there !

Engine tag says endt 675 / 235 hp

I did search the site , came up blank on t stat but iv been gaining knowlede on the motor .

Owner of a 78 Mack tow truck and i work it like a dog .