Frequent reader infrequent poster here. To make this short, My wife is in the Army and has been moved from Greenville SC to San Antonio Texas. My 1986 CJ7 remains in SC after two months here in San Antonio, which is no good. I am not at this time able to afford the approx. $1,000 dollars to ship it, and can't stand not having it around, not to mention it is ungaraged right now in SC where it has poured everday while I have been gone. So, like it or not, it's going to be driven here by me. My question pertains to highway RPM. I know this has been beaten to death several times, and I have read post after post. So one very simple question, At what RPM is my 258 going to not grenade itself while returning decent ( for a cj7 ) fuel economy? It is a T5 ( I know, I know, I know....boat anchor) with 3.31 factory gears, 2.5" lift on 31x10.50 BFG AT's, nuttered and pseudo team rushed ( bigger cap and better wires only ) with an MC2150 that was just professionally rebuilt. it runs, in my opinion, 8-9/10 ( still probably a small vacuum leak as it idles at 700, anything less and it gets unhappy). Consumes no appreciable oil etc. I have driven it 300 miles one way to the beach before, and kept the RPM's fairly low at first ( 5th gear ) but it seemed unhappy there. I am considering running in 4th gear at about 60 MPH for the whole trip, this would be in the 2300-2400 RPM range. Shifting to 5th brings this down to sub 2,000-2,000 RPM. SO..... I will do this trip in 7 to 8 hour increments. Will it hold 2,400 RPM without a problem? From what I have read this will produce better fuel economy and potentially better cooling that 1,900 RPM's. Thoughts and suggestions welcome...this trip will happen in about two weeks. I would like to post pics as I go, since I have to make the trip I am somewhat excited, seems like a nostalgic venture and fingers crossed for no big problems. Thanks in advance to all!
I run this exact same set up, minus the 5th gear. I kept it at 2400 and Got 18-20mpg with the help of the wind. Driving into the wind I got 14mpg. It's hit and miss. I enjoy driving my 7 on road trips. Take some tea and some tunes, sit back and cruise.
When I was stationed at Hunter Army Airfield in Savannah, GA. I drove my CJ from Concrete, WA to Savannah GA (3,522 miles) over a 5 day period. With NO stereo, only a CB.
Keep some food/drink with you and don't set a time table. Just get there when you get there. You're not going to set any speed records. Tip... draft behind a 18 wheeler. Let them cut the air for you. I had to do this across Nebraska as I had a serious head wind and with out someone breaking the air for me, I was down to 45mph and using a lot of fuel. I had my CB and asked the trucker if I could draft along as my brick with wheels was struggling to keep up.
Beat it to fit, paint it to match!
Thanks to all who replied! I am pretty sure the old girl will do fine..if not it will be interesting. I will cruise around 2400 without concern then. And nope, no big time table, I will have at least three i not four days to do it, should be plenty I did it in a day and a half in the grand 2 months ago, and traffic was way heavy. As long as no big mechanical failure occur and I achieve 15 ish MPG I will be happy. Everything else will be icing on the cake.
It will cost much less for you to ship it than drive it.
Look at the miles and fuel costs..........
I calculate APPROX. 1,153 miles. If you averaged 12 mpg that is 96 gal. National avg of $3.49 per gal, currently $3.15 by me, that would cost $336.00.
If you avg. 15 mpg that is 77 gal and $268.00.
I would worst case it and use the 12 mpg. If you can avg. the 60 mph then it is APPROX. 19 hrs. That is either 2 long days or 3 short.
If your cost to get to S.C. plus hotel and food for 2-3 day trip is less than than $663.00 then I say go for it. I would at least have someone take the Jeep to a local shop to have it looked over before you get there to be sure nothing is loose, missing or in need of immediate service. Would suck to have a breakdown over something easily addressed in advance.
Either way safe driving no matter how you get that CJ to Texas.
PS: No idea on the RPM question. Above my pay grade as I drive a '77 CJ7 with a 304, TH400 & 33x12's. Full Time 4wd makes for poor mileage. My best is 13.4 going from Columbus to the North coast of Ohio averaging 55 mph. Oh course I look AWESOME doing it!!
Just for comparison, I have an 86 as well with the t5 and 3.31 gears. But I run a 265 70 r 15 so I'm not as tall as a 31 inch tire, but just a hair over stock. With that combo, I can use fifth, and rpm range in 5th is about 2500/2600 at 80mph.
In your case your tires (31s) and your gears (3.31) put you in between 4th and 5th gear for the 2300 rpm plus needed to overcome the wind resistance for those higher highway speeds. 3.54 gears or smaller tires would be best.... But I'd try 4th gear at a slower speed like 60 to 65mph and or only try using 5th at much higher speeds so the rpm will be higher or just going down long grades. As said, lugging the engine at too low of an rpm will use more gas than a slightly high rpm at the same speed.
Thanks. Yes I should be able to get to SC for sub 200 bucks ( Airtran here I come ) and have family in the area for transportation. The jeep is known to be in good shape and recently maintenanced, so any catastrophic failure would be just that...an unannounced catastrophic event. Just hoping if i take it REALLY slow it won't stress the old jeep too badly or break the bank quite as badly