j_runner

HI guys... Can someone please tell me the easiest way to confirm my front DIFF gear ratio? I know how to check the rear... but for the front, do I have to jack all 4 tires off the ground and put it into 4HI and then follow the same procedure as checking the rear DIFF?

Thanks

d0ubledown

front & rear ratios are the same. easier to check the rear..so do it that way. or you can cross reference your axle code in your VIN tag off your door jamb with a ratio chart. schaefer has one onn his site sonoransteel.com

j_runner

Thanks for the info Sonny....I realize that the front and rears are the same or should be the same..... I just wanted to confirm that my DIFF's were the same.

I have checked my rear before and it's 4.10 with an elocker. Until checking sonoransteel.com I thought that all lockers were 4.30. Long story short, I purchased my rig used and just want to make sure that everything is proper. So is there an easy way to check my front DIFF? Or at least an easy way to check that my DIFF's are matched?

AxleIke

have you ever run it in 4wd? If you have, and your transfer case didn't blow up, then you have the same front and rear.

If you've never run 4wd, i'd repeat the procedure for the rear in the front like you suggested.

JamesD

Pull the driveshaft off. Top of the pinion itself has a paint swab. The color tells you your ratio. Unless somebody put aftermarket gears in it.

James

AxleIke

Do you have the link for that chart? I was going to post it, but can't find it.

But yeah, good point, forgot about that.

fork

im pretty sure you can put a mark on the tire and the driveshaft, stick it in neutral, and roll it until you make a full 360 degree rotation of the tire, while counting how many times the driveshaft spins (not very precise). beats ripping the whole thing apart though. mine doesnt have colors and ripping the front apart is not fun

pepsibluefloat

Ive never done this before, but maybe if your tires stick far enough out from the finderwells you can tie(or tape) one side of a piece of string on front tire and the other side to the string to the same point on the rear tire and with that side jacked off the ground(or both sides if you have lockers) put it in 4x4 and the string should go round and round the same speed...right? maybe im wrong im just trying to think of an easy way....

mastacox

Here's a good way to do it: go find some soft dirt, have someone outside the truck and watch your tires spin in 4WD (maybe mark a white spot on each one when you stop). Drive just far enough to go some multiple of a full rotation for your back wheels (say 5). When your back wheels have gone exactly 5 rotations, your front ones should have as well. If your front wheels spun less, you have a higher ratio up front, and if they spun more you have a lower ratio up front.

How did I come accross this knowledge? Easy, I broke my front diff in my '92, and swapped it with a junkyard one. Problem was, as soon as I tried out 4WD (driving on cement, straight) my driveline started binding like hell. Turns out, my replacement diff was 4.56 (even though they said it was 4.30's, bastards) and so my rear tires were spinning ever so slightly more than the front. Needless to say, this was bad.

In the end, driving in the dirt you're less likely to break something vitally important, such as your t-case. I KNEW there was something wrong 2 seconds after I shifted into 4wd on the hard stuff, but it's not necessarilly the recommended way to do it. I was fortunate and didn't do any damage to my driveline.

EDIT: when I replaced that diff, I took the "new" one apart and counted the ring and pinion. 43 ring gear teeth / 10 pinion teeth = happy

AxleIke

your rear tires were spinning less, not more...

But all so far are good ways to check, j runner, any luck so far?

mastacox

I have 4.30's, so for every d-shaft rotation in the back the tires were spinning 0.2325 times; but the front was 4.56, making the front tires spin 0.2193 times for each rotation of the d-shaft

So the front tires were under-spinning, or the back tires were over spinning. Either way, it was like I was trying to power-brake the whole time.

AxleIke

i guess it depends on how you look at it...The front tires have to spin at a faster rate to keep up with the rear, is what i was getting at, but your latest description also makes sense...anyway, regardless, its not a good thing.

j_runner

Well, I've read all your suggestions. I was hoping that I didn't have to take anything apart. As for finding a patch of mud around this time of year it'll be tough as it's all frozen LOL. I was thinking of marking the lowest point of the front and rear tires and driving around somewhere with good traction (to make sure the tires don't slip)... then get out and check that the marks were in the same position all the way around. Would that work?

From what you guys have wrote it sounds as if there would be catastrophic failure of the t-case if the DIFFs were mis-matched. I've driven in 4 HI without any issues on asphalt... is that a sure sign that the DIFFs are matched? Cause I've read on here that someone had 4.10 in the front and 4.30 in the rear and had no issues. Is that possible? Or was the issue that he hadn't put it into 4WD yet?

mastacox

Only if you didn't turn, you have to drive straight.

It's a possibility. Better safe than sorry... For the record you might also get the same effect by driving on the street in 4WD and turning, since it is not an AWD system (I'm assuming you don't what kind of 4Runner/Truck do you have anyway?). Driving on slick rock or the road in 4wd can be very taxing on your 4WD system.

I would say yes, as long as you didn't feel any strange binding in the drivetrain while driving straight. You do know that's a bad thing to do though, right?

I doubt it (unless all you did was low-traction stuff, and even then you wouldn't see any advantage so I don't see a point). It's a bad idea to have mismatched gears unless they're VERY close (like 4.10's vs. 4.11's). Overall, you want your gears to be the same.

AxleIke

yeah, if you've had it in 4hi on pavement, you are fine...Believe me, as mastacox said, you would really know it if it were off.

JamesD

Yes: http://www.4crawler.com/4x4/4R_TechInfo.shtml

James

j_runner

mastacox... I'm curious, what's wrong with using 4hi on asphalt? Generally, in slippery road conditions (rain or snow) I put it into 4hi as I find it much more stable and it prevents fish tailing. I have a 97 SR5.

As for the guy with the 4.30 rear and the 4.10 fronts, this was someone who did a e-lock swap in the rear. So it wasn't intentional.

Thanks for all the help guys!

j_runner

I did a search and realized what you were implying.... and NO I never use 4HI on bare dry asphalt....

Last night I marked the front and rear tires and drove it in 4HI really slowly, looks like the DIFFs are matched as when I got out the markings on the front and rear tires were more or less in matching positions ... very close at least... I attributed the very minor differences to the road conditions as they were partially snow covered.

Thanks again guys for all the help... yotatech rules!:bigclap:

Travis Russell

I think after 3 rearend 3;73 all busted my front diff is lower it's half ton with 35s I turned front tire 1 turn shaft was 2.25 any help be greatful

Malcolm99

What? you broke 3 rear ends? your replying to a 2007 thread, you should really start a new thread with ALL your vehicle info, you can decode the ID plate on the door jam for example VZN185L-GKPZKA(The option is the e-locker) [other options is the tire size on the ID plate for some] so my truck is 4.30 ratio, if you have the original 3rd member the gear ratio is stamped right on the ring gear and I assume the front ring gear aswell. If you have RZN180L-GKMSKA and the smaller tires on the ID from factory it would be 3.727 ratio. Usually the front diff is the weak link.

https://www.sonoransteel.com/downloa...aGearRatio.pdf