T18 Id?

How do you tell the difference between the low gear(6.32.1) and the
(4.2.1) T18? The one I am looking has these markings.
Case-- T18-1B
Tag on shift cover--5358092 13-01-187
How to tell which one this is?
Thanks..

 

put it in 1st gear and turn the output shaft 1 revolution while counting the number of turns of the input shaft. if it makes 4 revolutions it is a 4to1, if it makes nearly 6-1/3 it is a 6.32 to 1

JB

 

the tag number indicates it came from a 1978 CJ model
those were the low 1st gear if I recall

 

Simple as that. If it is hard to turn, spin the input shaft.

You can't go by tags or castings, someone like me may have changed it!

 

Thanks for the replys, the trans is in a vehicle, so I can not turn shafts. How do you decode the tag, or where can I look to find decoding info?
Also on the case where it says T18-1B, what is the 1B for? Others that I have seen had 1A on them.

 

Jim gave you the decoding info above. You can decode the Jeep PN using the old parts books. I don't know of any way to decode the B-W number. The casting numbers in the case don't help.

If it's in a vehicle, and that vehicle looks like a '78 CJ, then it's almost certainly the right tag, and a wide ratio transmission. The close ratio T-18s were only used in the 72-76 CJs AFAIK.