First Time on the Interstate

[Mick]

Well... I finally have my 74 CJ5 in pretty good running condition... It was 4 months of fun that included a lot of wrench time, welding, painting, fabrication, and modification (of course, some cussing as well)...

So, I take it out on the open interstate today, 40 miles round trip, to get some gas in the Jeep and the gas cans...

While at the gas station, when I pulled off the gas cap, there was a big out rush of air from the tank... Like the tank is not being vented properly... Even now, sitting in the garage (an hour later), I can hear the gas tank being vented slowly... I do not think this is normal... What should be the normal venting of the gas tank? Should you hear the venting while the gas tank is cooling down after driving?

Another thing I noticed, while sitting in the garage, is a small oil drip from the Transfer Case ... I believe the output shaft (drive shaft) seal is leaking... How hard is it to change the seal?

And lastly, I clocked my Jeep while going down the road... I used an App on my phone that connects by GPS in order to give me speed... I have used the App in my other vehicles to verify its accuracy... It is pretty accurate (within 1 mph)... It appears that I am going to have to change the speedo gear in my Transfer Case (Jeep was lifted by previous owner with 33's on it)... If I know the Jeeps speedometer reading and the true speed of the Jeep by GPS, can I calculate the number of tooth gear I would need for the speedo?

Thanks for the help guys/gals!!!

 

[Torxhead]

The '74 CJ5 did come with a fuel tank vent system, you should be able to find it on the web or a CJ specific repair manual. The output shaft seal installation should be found on the net. Better to hear from somebody in the know about that Transfer Case gear, from what I have heard it is not that simple.

 

[Hedgehog]

Your fuel tank should have a venting system. Look at the fuel tank from the drivers side wheel well, there should be several gas type lines there. A fuel line, a fuel return line and two nipples comming from the very top of the tank. If you have a simgle line looping between the two nipples someone has replaced the vent lines that interact with the charcoal canister located under the hood by the driverside fender. It can be difficult to find vent components. Without'em the Jeep can smell very gassy.

You might not need to replace the seal at all, a little drip is nothing to worry about. Most Jeeps leak a little. Mine is now pretty good, ut when I got it there were several leaks. Most people get one of those long trays made for catching oil and just keep it under the Jeep while it's in the garage.

Replacing the seal isn't that difficult. I did it on my Dana 20 , but it was on my work bench at the time. You will need an impact wrench to remove the big nut for the propeller shaft, toss the nut it is a one time use item and you should have one in the rebuild kit. Then remove the 9/16" bolts around the housing. The housing has a BIG flange so it might take some doing to wriggle the housing off. I got a rebuilding kit that came with a bunch of extra parts like a felt whick and other goodies that weren't needed for the Dana 20 I have. A warning here, there will be some shimes between the main bearing and the gear (I think it was a gear, can't remember), these shims are paper thin so be careful not to damage them.

Removing the seal was a bit of a chore. On my first attempt I tried my brand new seal puller. These things usually work well, but in this application it worked like a can opener tearing the seal and not removing it. I ended up using a long punch that could reach down fron the inside to catch the lip of the seal. It took several attempts and the seal came out in tatters, but the seat wasn't scared. At this point clean up the gasket surface and carefully reseat the casting.

You probably noticed this already, the speedometer drive gear will be fully exposed and easily changed while the casting is off. There must be a color coad, mine was bringht Orange .... Hmmmm that is if I'm remembering correctly.

 

[Mick]

Hedge and Torx... Thanks for the replies...

Torx: I have found "how to" guides on the net... I was just wondering if someone here had first hand experience on the items I listed... Not that I don't trust stuff found on the internet, but, it's just that, well, I don't trust stuff I find on the internet... Other than those that frequent this site and a few other sites!

Hedge: Concerning the Transfer Case output seal... You described exactly what I was looking for... Someone with first hand experience... You know, that someone who says "when you do this be careful of x, y, and z"...

Concerning the gas tank vent system... I will do some digging and see what I can come up with... I know I do not have the charcoal canister which leads me to believe that I probably do not have a vent on the tank... I guess I will have to come up with the necessary parts and install that system... Sounds like a lot of fun... :/

Concerning the speedo gear, I have had mine out before... A socket with shaved sides (thinning the wall thickness of the socket) a rachet and some elbow grease, and it came right out... I had an old speedo cable break off inside the gear and I could not get it out without removing the gear... Since then, I have upgraded to an electrical speedo that uses a pulse generator connected to the speedo gear... I was just wondering if there was a quick guide that said something like "If your indicated speed is X and your actual speed is Y, then you need this gear"... I guess I can use the charts that show differential gearing and tire size to get the correct speedo gear...

Thanks for the replies!

 

[sketchy]

Concerning the speedo gear...[snip]... I was just wondering if there was a quick guide that said something like "If your indicated speed is X and your actual speed is Y, then you need this gear"... I guess I can use the charts that show differential gearing and tire size to get the correct speedo gear...

If you know how many teeth you have now, use the ratio of indicated (speedometer) to actual (gps) speed as a multiplier to get how many teeth you need. You don't need the charts, diff ratio, tire size, etc.

Or you can use indicated distance vs. actual distance. Since I just did this today, here are my numbers. I drove 20.0 miles by the speedometer, 21.7 miles by google maps. 21.7/20 = 1.085 or 8.5% fast. I pulled my gear and counted 31 teeth. 31/1.085 = 28.5. Since nobody ever has 28.5-tooth gears in stock I need to pick a 28 or 29. I round down to 28 so my speedometer reads a little fast. (I have a couple of zero tolerance enforcement areas around here.)

Where you have to think a little is figuring out if you want to go bigger or smaller. If you are going down the road at a certain speed, and your speedometer reads too low, you need to make the speedometer cable turn faster. Changing to fewer teeth makes a driven gear go faster so the (driven) speedometer gear needs fewer teeth. If your speedometer reads too fast you need more teeth.

The worst thing you can do here is multiply when you should divide or vice-versa and end up twice as far off as you started. Verify that you are moving in the right direction by looking at the gear charts.

 

[Hedgehog]

You could do all this the right way ooorrrrr you can cheat. I use my Vehicle GPS to do both my distance and speed, why the odometer has proven to be accurate, but the speedometer was all over the place. Surprisingly enough the thing has settled down and has become consistently 6 mph slow. In the situation where the speedometer is consistent, mark the glass at your important speeds. I have gotten some of that body tape used for pin striping and replace the marks with nice looking marks. It's cheap, it's easy and it works.