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Hey new to the site ,but have been reading here for a while.I have a 1975 CJ5 with a 3 speed T-14Transmission and 3.72 gears would it be better if i went to a four speed?
73 CJ5 4.0 head on a 258, HEI, Holley Projection w/ 4.56, Detroit lockers Narrowed D44 front and full float D44 rear T14 w/ D20 4 wheel discs, 38.5 Boggers
I have a T-18 with 3.73 gears it does pretty good but I have a Tera low 3.1 in my Dana 20 so it helps. I'm running 33 tires also. What size tires are you running?
It pretty much depends upon what you want to do with your jeep. The “granny” low 1st is nice to have for crawling. Crawling in my mind does not mean rocks per say as it could just be idling down an old logging road trying not to beat yourself, passengers, and jeep to death as you go. The T-18 is the most common swap and in fact the 1972 to 1979 CJs had a T-18 option offered from the factory making it an easy swap; there are a lot of nuances to the T-18 but all in all you won’t find a more “direct bolt in” offering. Here is a link that will help shed some light on the T-18 :
Hey new to the site ,but have been reading here for a while.I have a 1975 CJ5 with a 3 speed T-14Transmission and 3.72 gears would it be better if i went to a four speed?
If you play with this a little, you can see what a change in one part would do to your compound crawl ratio. For instance. Your set-up you currently have 23:1 absolute low ratio... For crawling, climbing steep, and real rocky areas, this is way to high. (high meaning, numerically lower number:1 - 20:1 is "worse" than 21:1)
If you can play with it a while you'll notice the best way to get the most change is a granny low gear tranny (like the T-18 6.32:1 T-18 )
If you did the expensive terra low, or the bronco / d-18 gear swap you's be at 3:1 vs 2:1 which would only bring you to: 35:1 (which is still better)
If you instead change your gear ratios to 4.56 it would only bring you to 28:1 without the above mod, or 42:1 if you did them both (approx 1-2k$)
If you find and drop a 4 speed granny low version of the T-18 :
and did nothing else = 47:1
Did the t case too = 71:1
with both, and re-gearing (4.56)= 86:1
According to the following, this would be a very respectable ratio, even without the gear ratio in the diffs being re-done:
"Crawl ratios in the 60's are quite capable; in the 80's, very respectable, in the 110's, impressive and anything beyond the 130's is usually considered the point of diminishing returns." (Novak's site) from the link above.
Now we don't know the tire size you are running, or even if this is what you meant by better... So let us know those.
I agree with the others - Depends on what your future plans are and what you want to do. I ran my 73CJ for many years with the stock 3 spd and Dana 20 . I had a great time and it works fine. However, the lowest ratio with this combo is about 28:1. I had to hit some trails a bit harder than I wanted.
There are three items to change: 1) Front/Rear Axle ratio, 2) Transmission , and 3) Transfer Case gears. Review the combinations and make a cost estimate.
Over the years, I have eventually changed all three on mine. It crawls great, but I often wish I had a better highway gear.
One of the other posters mentioned that the 3 speed shifts from 1st to Rev quickly in a straight line. This is useful and I do miss that now that I have a T-18 .
I might suggest that keeping your 3 spd and getting a lower gear for the Dana 20 could be enough. You would get a lower crawl ratio, yet keep the stock axle ratios for highway economy. Also, your driveline angles are easier since you keep the stock lengths. The T-18 combo is at least 2 inches longer, which is significant considering the short wheelbase of the CJ5 .
