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Glenn's
85 CJ-7 has little problems off road. However one issue is a crawl ratio that
is somewhat high (32.3:1) The T-176 transmission has a 3.52 low gear and
Glenn's Jeep has 3.54 axle ratios. The Dana 300 transfer case offers a
2.62:1 low range which makes Glenn's Jeep tolerable off road but it could stand
for some improvement. A transmission or axle ratio change would be costly and
time consuming.
TeraFlex
offers a low range kit for Dana 300's that increases the low range ratio to
4:1. The kit consists of 5 gears that replace all of the transfer case's original
gears. This modification requires some grinding to fit the idler gear into
the case.
After completion this small
change will improve the Jeep's ratio to 49.8:1 from 32.3:1 while still maintaining good
cruise rpm and street drivability. Follow along as this project
progresses.
This table is a comparison
of crawl ratio between the TeraLow and stock gearing. The Jeep is equipped
with 3.54 axle ratios. The formula is gear X transfer case X axle ratio =
crawl ratio.
| Trans Gear |
2.62:1 Gears |
4:1 Gears |
| 1-3.52 |
32.6 |
49.8 |
| 2-2.27 |
21.1 |
32.1 |
| 3-1.46 |
13.5 |
20.6 |
| 4-1.00 |
9.2 |
14.1 |
| R-3.52 |
32.6 |
49.8 |
You can see the improvement
on 1st gear. Also 2nd gear is almost the same as the original 1st, this
will come in handy when not in an absolute crawl situation.
There are several models of
the TeraLow, there are TeraLow's for Dana 300 (4:1), Dana 20 (3.15:1), Dana 18
(3.15:1), and NP 231 (4:1). Check out the TeraFlex
web site for more detail.
Now onto the project.
Stage 1 - Buy Stuff and
Extra Transfer Case
Glenn picked up the TeraLow from OK Auto and
ordered a rebuild kit for the transfer case. We also picked up a used Dana
300 to do the gear swap, this way the Jeep is left intact until ready for
installation.
On to Page 2
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Onboard
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