Axles, Gears, Trans... How do I tell what I have?

[PhattyX]

AC Compressor troubles....

Well, since I bought a Jeep with an engine swap, I don't want to assume what kind of axles and gears I have. Conveniently, I also got a spare set of axles and a 4sp transmission with the Jeep. So, the obvious question is... How do I tell what they are / what gears are in them?

Any idea where I can look up / decipher the codes tagged on some of the parts?

This is my first dip into gear ratios and axles. I'm not really sure what the goods and bads are either. So, any and all information would be greatly appreciated. Thanks much!

X

 

[stacker46]

CJ, YJ, TJ and what year? Try this site out though, it may help you identify the axles: http://www.off-road.com/jeep/tech/axle/

 

[PhattyX]

It's an '84 CJ7. I have no idea whether the stock equipment is in there right now, though.

BTW- Holy crap! That site's got a lot of info.

Thanks,

X

 

[Junkpile]

http://www.jeeptech.com/wiki/index.php/Transmission


Since it's got an AMC 360 in it, I'd assume it's a factory transmission. If so, the possibilities are an SR-4, T4, T-176, or a T-18. The heavy duty T-18 is easy, it's a monster. It's so big, and plus the fact that first is a granny gear, you can't miss it. The medium duty T-176 is smaller and has a smooth case. The other two are considered light duty and have strengthening ribs cast all over the housing. The Tcase should be the great little D300.

 

[redrooster]

The axles are more than likely going to be a Dana 30 front and AMC 20 rear. Look up the Dana 30 cover plate design on that site, it's hard to describe. The model 20 cover is a perfect bowl shape. If both are stock then they are the "widetrack" axles which means they are several inches wider than the 79 and back models.
You can look for a small metal tag on one of the cover bolts that will tell you what the gear ratios are. If the tag is missing then you will have to open the cover and count the ring gear and pinion gear teeth. Divide teh higher by the lower and you will have your ratio. A common ratio for that era was 3.54, but they also had 2.73, 3.73 and 4.10 in 4 cyl models.

 

[Bounty__Hunter]

If you pull the diff cover (good idea to change the fluid since the jeep is new to you) look for numbers stamped in the edge of the ring gear facing you. Should be a pair of two digit numbers. Divide the larger number by the smaller and you should have your gear ratio. Can't always trust the diff cover tag.

 

[Junkpile]

Phatty, did you ever figure it out? What's it got in it?

 

[PhattyX]

OK, so far here's what I've got:

Currently, it's got a 5sp T-5 w/ D300.

The spare 4sp looks like a T-176, but I've still got to verify that by casting number. The attatched transfer case says D300 on it and is on the pass. side. Since the write-up says a D300 will be cast with C300... , I'm going to reserve judgement 'til I figure out what transmission it is.

As for the axels / gears... 4 axles : 0 tags. I'm going to be sick one day next week and take the covers off.

I'll keep this post updated! Thanks again for the links. They're helping a lot!

X

 

[PhattyX]

"'Curiouser and Curiouser', thought Alice."

The spare trans is definately a T-170 series of some sort. The pics are identical and the casting number is close. Anyone know how to tell the diff between the 176, 177, & 178? This trans' casting number is C-2604208. I double and triple checked it. It's clean, there's no mistake. That's not a 3 at the end. The transfer case is a D300... I found the casting number on it. Either way, I'm pretty sure I'm gonna stick with the T-5 for the lower 1st gear and the OD gear. I'm not sure what the "real world" difference is between a "Light-Duty" and a "Medium Duty" trans is. Any input would be appreciated as always.

And now for the axles...

The spares are a Dana30 and an AMC20 as suspected. They are 3.54's... and they're not going on. Any idea what I should ask for them?

On the Jeep is an AMC20 3.11 rear, but I could not decipher what the front is. It don't look like no Dana30 to me. The cover looks like an egg shape with straight sides. The bottom looks like the YJ D30 pic on that axle site. I'll have to snap a pic and see if anyone knows.

So, what's the problem, right? Well, I took a trusty tape measure to verify they're Wide-trak (Why bother, it's an '84!)... From the inside of the brake drums, it's 50.5". Umm... please tell me I measured it wrong. Either that, or this isn't quite an '84. Well, the AMC20 codes are a bit different depending on which Axle it is, but conveniently, it doesn't matter, the gears are the same for these particular codes (A & BB). Yeah, if that's a Wide-trak rear axles, it's got Trak-lock.

Any help from the axle God's would be greatly appreciated right now. Did I measure wrong? Is there another way to tell whether they're Wide or Narrow? Is there something else I can check to see if'n this here's an '84 frame or not?

Thanks again, all!

X

 

[Junkpile]

The T-176/7/8 is much more durable than the T5. It sucks too, because as you pointed out, the T5 has good ratios. It's not worth the trouble. When it breaks, throw the good one in there. You'll need new driveshafts when you do.

The WMS to WMS measurement on the widetrack axle is about 56". All of the widetrac axles had 5 bolt hubs, along with the 80 and 81 narrowtrack. Prior to that they used the stronger 6 bolt version. For pricing, in this area a widetrack front D30 goes for between $350-$500 complete if they know what they've got. People don't appreciate this axle, but they fail to realize it was only made for 5 years and the supplies are running out. In the not too distant future, I can see Jeep resto freaks paying big bucks for them. I'm proud to say I've done my part to increase the price by destroying a couple of them

The front shock mounts will be longer on a widetrack frame. On the narrowtrack the mounts are short and stick up about an inch or so above the frame rail, the widetracks are a few inches taller. I know there are more differences than that, but I can't think of them. The 76 was a little different and was crack prone in the front, but after that they didn't really change much until the YJ.

 

[PhattyX]

RE: Re: RE: southwest florida

I'm a little be confused about gears. I have two sets of rears 3.11s and 3.73s. The 3.11s have trac lok. "What are the pros and cons of each?" Everyone seems to be going with lower gears, but I'm not sure as to why.

Would going to lower gears (3.73s) make the CJ "less quick"? Also, if I did the swap, could I lock the rears? I assume doing that would be a permanent thing, unlike LSD. Correct?

Thanks, as always,

X

 

[Junkpile]

In most cases, a lower gear ratio will improve acceleration. It will always reduce top speed at a given rpm if no transmission gear changes or tire size changes have been made.
The best gear ratio for a particular application depends alot on the rest of the drivetrain, the engines powerband, and the size of the tires. Lower gears make it easier to turn taller tires, that's why most people with a four wheel drive eventually regear after putting on bigger tires. When you change the tire size, you are effectively changing the gear ratio. Going up a couple of inches in tire size will make a 3.73 ratio act more like a 3.27(for example).....so at that point you would regear to a 4.11:1 ratio to make it perform like it did with the 3.73s and the smaller tires.

 

[GaryMB]

you could lock either rear, and yes it would constantly effect the driving characteristics. As for the gears, if you want every last bit of offroad performance out of the jeep or are running huge tires then go with the 3.73s. They will lower your crawl ratio ever so slightly. However, if it is not a hardcore rig or has oversized tires, then i would do whatever is easier since the T5 does have overdrive and a decent first gear.

 

[Sparky-Watts]

I'm going to be sick one day next week and take the covers off.

And here I thought I was the only one that got sick to work on my Jeep!! :lol:

 

[PhattyX]

Painting Help

Sparky - Isn't that what sick days are for?

Thanks for the input as always, guys. I was mistaken (trying to do two things at once). I have 3.11s and 3.54s (not 3.73s). The 3.54s are open to the best of my knowledge. I've read things where people say they have in-cab switches for the lockers. Does this mean that there are setups that would allow me to disengage the locker while on the street / highway?

Evnetually, I'll lift it further and put some bigger tires. 32-34's. Would it be better to start looking for 4.11s? Bascially, as it is, the 5.9L has a whole lot of torque, but it simply isn't very quick at getting the Jeep moving. Once it's moving, It's a beast. I'd like to get that type of performance through it's whole range. While I plan on taking it wheeling, it'll spend most of it's life on the road. Have I missed the point, or would finding even lower gears be what I'm after?

-X