popping noise?

[blake22]

Im new here and would like to start by saying hi. Ive been reading on this site for a few months now but just joined. Ive got a 79 k5 blazer i just got going in te last few weeks. Its 6in lift with 38.5 super swampers 355/granny 4 speed/205 with stock axles (as far as i know). Im sort of new to the 4wd thing but i have a good basic knowledge. today was the first day i tried to engage 4x4. put the transmission and transfer case in N, locked the hubs and put the TC in 4 low. let out the clutch and it was crawling along but after about 10 feet or so it poped and kind of jerked the truck. im pretty sure its not my driveshaft as i have ground all the tabs down and added a angle shim under the front axle but maybe? What could happen if i had diffrent gears in the front than rear? would the TC just bust open what? maybe my hubs have some sort of problem?

[Stocker]

Welcome from NorCal.

As soon as I read 'popping & jerking', I thought 'different gearsets front to rear'. Definitely check that.... they need to be the same! If different, any number of things might break -- or the drivetrain could just bind up with no breakage, if you're lucky.

You might have a broken hub, broken u-joint, broken axle / splines.... just gonna have to get underneath and start inspecting everything. Are the driveshafts long enough for your lift? if not, the splines might have popped out of the yoke.

[blake22]

well i have been through alot with the driveshaft and i think i have it right as far as length. After i made the post i went outside and tried to get it out of 4wd and the hubs wouldnt turn and the tc wont come out of gear so i started it and rolled it forward a little and nothing changed so i just messed with the tc shifter a little and started to drive it around back but no popping or anything. But i can tell its in a lot lower gear now. so after driving it around for a little while and no problems i popped the clutch and the front tires seem to have spun so i guess the shifter was just not happy? could this be true?

[JPBrecheisen]

Was it just a single pop? Did it act like it was in nuetral when it popped?

Is it a possibility the TC shifter wasn't "fully in" when you brought it into 4L?

I have had my TC "pop" once because it felt like it was in gear (4 Wheel), but it apparently was only about 1/2 way when I engaged the front axle. No grinding, it just simply popped into nuetral when I put a load on the gears when i started moving forward. Maybe that was it?

[blake22]

i think thats just what it was. it wasnt ingaged all the way. i have a few more questions thow.. i cant seem to get it out of 4x4? the tc wont come out of 4lo the hubs wont unlock either? do i need to roll the truck and try to unlock the hubs or something then put the tc in 2 hi?

[Stocker]

Probably just in a bind, try backing up a few feet or so. If you just can't get it out of 4WD, jack up one of the front corners. Be ready for it to unload quickly (brief sudden spin of the tire). If that's your problem, it's a good illustration of why not to engage 4WD unless you're on a slick surface where the tires can slip.

[blake22]

Originally Posted by Stocker

Probably just in a bind, try backing up a few feet or so. If you just can't get it out of 4WD, jack up one of the front corners. Be ready for it to unload quickly (brief sudden spin of the tire). If that's your problem, it's a good illustration of why not to engage 4WD unless you're on a slick surface where the tires can slip.

Yeah i turned it around in the street earlier and it was jerking all around. not a good idea. How can i go about seeing what gears i have in the front without pulling the cover? i had it jacked up and turned the wheel one turn but the pinon only turned once? should i have the hubs locked in?

[Stocker]

Jack up the RF tire with its hub locked in. Watch the front driveshaft. Rotate the RF tire 2 full turns -- the number of driveshaft rotations will equal your approximate gear ratio. My driveshaft rotated just over 4 times, and I have 4.10 gears.

[76k10]

It sounds like the truck does move it 4wd. If your gears were mismatched, it probably would not move at all.

[JPBrecheisen]

Originally Posted by blake22

Yeah i turned it around in the street earlier and it was jerking all around. not a good idea. How can i go about seeing what gears i have in the front without pulling the cover? i had it jacked up and turned the wheel one turn but the pinon only turned once? should i have the hubs locked in?

If the axles haven't been worked on in the past, some of them have a small tag under one of the diff-cover bolts. It will have the ratio on it. Only way to be sure is to look at the stampings on the ring gear. I know its a mess, but that way you'll know for sure.

Are the axles original to the truck? If they are the original axles, I'd kinda doubt you have different ratio's in there, but anything is possible. See if you can see a tag on the diff covers. They can be over-looked because they get hidden by years of grime.

How about these tires you have? Are they all same brand etc? Tires run big, small, etc just like clothing and shoes. Just because you have the same size on the side wall, doesn't mean they're all the same diameter. Especially if they are different brands. They won't be off by much, but if you've engaged the front axle on dry pavement (bad idea, so don't do that anymore), its possible there is "tension" on the gears preventing your from getting it out of 4L. Its just trying to pull the transmission out of gear when you're speeding up...the tension on the gears keeps you from pulling it out of gear, but as soon as you let off the gas, it'll pop right out. If you have anything different from front to rear (gear ratio or tire diameter) there will be tension on the gears in the transfercase and you may not be able to get it out of gear.

Some lock out hubs can be a real PITA. I have set of old spicer hubs on my 72, and they can be a real peach when trying to go from lock to free. Try getting the front wheels off the ground and see if you can't get the hubs unlocked.

[JPBrecheisen]

Originally Posted by blake22

Yeah i turned it around in the street earlier and it was jerking all around. not a good idea. How can i go about seeing what gears i have in the front without pulling the cover? i had it jacked up and turned the wheel one turn but the pinon only turned once? should i have the hubs locked in?

In order to check the ratio like Stocker is talking about, you will need the hub locked in so you are actually turning the axle and thus the ring gear.

Understand when you're talking gear ratios, most people just phrase half the ratio equation. Like Stocker said. He rotates his tire/axle/ring gear 1 full turn, and his front drive shaft turned about 4 times. This is a 4.10:1 ratio.

what 4.10:1 effectively means is: for every 4.10 rotations of the pinion gear (front driveshaft), the ring gear (which turns the axles and tires) will turn 1.0 times.

So Stocker has the easy way to check, but it might get tricky because some ratios are kinda close together like 3.54:1 or 3.73:1 etc. Either way, you need to be rotating the axle shaft in order to do it this way, so you'll need the hub locked in to make sure its rotating the ring gear.

Keep after it, you'll get if figured out.

[blake22]

Originally Posted by JPBrecheisen

In order to check the ratio like Stocker is talking about, you will need the hub locked in so you are actually turning the axle and thus the ring gear.

Understand when you're talking gear ratios, most people just phrase half the ratio equation. Like Stocker said. He rotates his tire/axle/ring gear 1 full turn, and his front drive shaft turned about 4 times. This is a 4.10:1 ratio.

what 4.10:1 effectively means is: for every 4.10 rotations of the pinion gear (front driveshaft), the ring gear (which turns the axles and tires) will turn 1.0 times.

So Stocker has the easy way to check, but it might get tricky because some ratios are kinda close together like 3.54:1 or 3.73:1 etc. Either way, you need to be rotating the axle shaft in order to do it this way, so you'll need the hub locked in to make sure its rotating the ring gear.

Keep after it, you'll get if figured out.

i jacked up the pass side with the hubs locked in and spun the wheel two times. the pinion spun about 3 and a half times so i guess i have 3.54 gears. i wasnt sure of all the factory truck gears but now that you mention the 3.54 that sounds about right. ill check the back after i weld it up this afternoon to make sure they are the same. but i have driven it enough now that i think something would have broken if i had diffrent gears in the front and back. the tires are all the same size, brand and even wear. i know the all the problems and bad things that come with welding a diff but i have sucessfully done it 3 times now. the truck is a straight mud truck with no street time. Thanks for all your help!

[blake22]

I think i have a problem!!! after changing the oil in the front diff i went to the back and the ring gear looks alot thinner like a higher gear would! If i remember correctly the stock 12 bolt in the rear has a larger ring gear than the front 10 bolt dana 44 right? so wouldnt that make the ring gear in the back thinner? or am i thinking about this wrong? i found these numbers on the ring gear in the rear.
439798 17 47 gm 2 801 does this mean anything?

[blake22]

after welding the rear together i spun the wheel one time and the pinion spun 2.6 ish times? my gears are diffrent arent they?

[Stocker]

I think at this point I'd pull the covers off and count the teeth on the ring & pinion, front and back.

Divide the number of teeth on the ring gear by the number of teeth on the pinion. That's your gear ratio.

[JPBrecheisen]

439798 17 47 gm 2 801

17 and 47 should be your teeth count on your ring and pinion gears. 47/17 = 2.76 gear ratio. This would coincide with what you saw out of the driveshaft rotation of about 2.5 times.

the 439798 should be the part number.

Looks like you might have different ratios in that thing after all?

[blake22]

yes after counting the teeth on the ring and pinion i got that same 2.76 well i think this will be the only time ill be happy to hear i have 2.76 gears in the front because im supposed to be at a mud bog tomorrow morning at 10. hopefully i did something wrong checking the front the first time!!

[blake22]

ended up taking the front drive shaft off for the bog and breaking the rear one it the mud pit! Well actually the pinion yoke but it was fun!! going to dana 60s soon