1976 Jeep Cj With Stock T18

I am looking at a 1976 CJ that has a stock T18. Without removing the top cover to check the ratio. How good of call can one make with seat of the pants run out in 1st gear. Basically it is all stock sightly larger tires 258 engine. If I was in 1st high and it ran out to say 10 to 15 miles an hour. Would I be able to make a good judgement call if it has a 6.32 or 4.02 ratio?

 

1976 is close ratio. First year for wide ratio is 1977.

You could calculate it if you knew the axle ratio (likely 3.54:1), tire height, the idle speed and the forward speed at idle.

 

76 is a crossover year with the later T18's being wide ratio.

 

Could be. Lots of goofy stuff went on with specs and equipment. However, the parts book only shows one model 80/90 T-18 input shaft for 1976, with a clear division from both 1975 and 1977. No footnotes. My understanding is that '76 is a unique configuration, close ratio and a 1-piece bell - no plate adapter.

 

I owned a late 76 T18 (J6M) with 6.32 gearing.
Had the 7 shims between the skid and frame.

 

Mark your driveshaft, put it in 1st gear and have someone count driveshaft revolutions compared to 1 rotation of the tires.

Mike

 

If I was a gambler I would put my money on it being a 4 to 1 transmission. I was able to find a chart showing with stock tires 1st gear high at 4500 rpm's the 6.32 to 1 would be about 17 mph. And the 4.02 to 1 at 4500 rpm's would be about 27 mph. Chances are it does not have a tachometer but if I rev it out a bit and only get to about 15 or 25 miles an hour. I could be pretty certain which gear ratio it is.

 

It's been a looong time since I've driven one of these CR 4-speeds, but I recall that it seemed kinda normalish to start out in 1st, since 2nd is also a proportionally higher gear - it's literally a closer ratio. You could drive around in 2-3-4 but from a full stop, dropping into first seemed like the right thing to do. This is different from the WR vehicles, where 1st seems really differently low and starting in 2nd more appropriate to regular driving. I'd think this would be even more pronounced with the '76 since Jeep changed the standard axle ratio from 3.73 to 3.54. So I'd think you could tell by driving the Jeep.

 

Or pull the top cover and count the maindrive gear, the 4.02 had a 23 tooth and 6.32 has a 17 tooth.

 

If you have access to the top cover, the Borg-Warner number for a '76 close ratio is 13-01-000-168, Jeep PN 5355010. A '77 wide ratio is 13-01-000-177, 5356735. If the transmission was replaced in service, it could be a wide ratio 13-01-000-168, 5358092, the service part for a '77.

 

I have a 6.32:1 and will tell you 15mph is pushing it for 1st. Typically I get to 5-7 and shift. With the shorter gear Id bet it idles at 5mph. Really on pavement driving I start in 2nd.