Grinding Noise

[dmowrey3@comcast.net]

Just got my 1953 M37 up and running and Im getting a grinding noise when I let off the gas , just installed another 3rd member in the rear and still have the same grinding noise . Wondering if something could be grinding in the transfer case . Any help would be appreciated . Also Im running 39.5 x 16 tires , can I run the truck at 50 mph with out damaging the drive train . Transfer case makes a hell of a whine at speed and sounds like it could fly apart if I go to 50 mph .

[RMS]

if your use to driving a honda civic the m37 drive line will allays sound grindy.

is the noise present in all the gears? if it quiets in 4th then its likely the trust washers on the counter shaft in the transmission. if its in all gears and you don't feel it in the shifter nob then it could be the T case. what does the oil look like and what are you running for oil? heavy 90w diff oil in the tcase will cause poor flow to vital parts and particles to build up. then the driven shaft clutch gear and the two speed clutch gear gets paced. they stop engaging fully. messes up the mesh and chews away at the driven shaft upper and lower .

when you installed the new 3rd member did you inspect, repack and torque the wheel bearings then use the proper gasket of the correct thickness ?

[dmowrey3@comcast.net]

Rig is modified with Chevy 350 engine and Turbo350 3 speed automatic , NP 200 transfer case and 5.83 3rd members . I am using 75 - 90 weight oil in transfer case and diffs , 3rd member looked like it had been rebuilt at some point , Bought it from John at Midwest as a used part , It appeared to be okay and was installed correctly . The noise is only when there is no pressure on the drive train and goes away when pressure is applied . Truck is also lifted and there is 10 inch drop from transfer case to rear axle , I will need to use a double cardan to get the proper pinion angle at transfer yoke . I don't feel any slop at the transfer yoke or the 3rd member so I am not sure what could be causing the grinding noise . Thx Dave

[RMS]

great looking truck Dave ! can we get some more pics.

glad to hear the 3rd was installed correctly lowering the chance of breaking an axle.

the woman took apart 4 tcases, everyone was run on diff oil (rather than 50w trans oil) and the driven shaft was warn the selector gear was packed with filings. there are needle bearings on that driven shaft that will starve and run in a grey goo. all the trust washers will suffer, preloads will vanish and earplugs will be needed. this is exacerbated by drive line speeds over 3400rpm

here's a little story about drive line speed

Harry Eiserman (RIP) got his M37 from the Canadian military in 1958. in 68 he installed a 315 hemie and started making runs north along the Alcan hwy. Gas was cheep but the guys at Bens truck parts in Vancouver were losing their shirts because of the warranty they offered on their work. You see Mr Eiserman was in about every other month for warranty work on his third member. often they would have to install a new unit as his was not salvageable. Ben of Ben's truck parts would give his guys shit for not setting the diffs up correctly and apologize to Harry for not getting it right. However Ben did not know that Harry would often travel with his foot planted to the floor screaming along the highway doing 90mph @ 5000rpm. the diff would get so hot that it would boil blow out the seal and puke out all its oil. In 1973 Harry installed 4.89s, reduced his drive line speed and Ben never had another warranty issue with Mr Eiserman

[dmowrey3@comcast.net]

Thx . Plans are in the works to send the 3rd members to Bob Stahl and regear to 4.89 and I will change out gear oil to a lighter weight oil in transfer case , I hoping the noise is in the 3rd member as I was already planning to get them redone .