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blazerbrad · 07-06-2018, 08:30 AM

In regards to the transfer case and differential gearing to make a TH350 or TH400 work it's like anything else in that you need to make sure you have the right gearing in the other components. With a SM465, or other granny geared manual, the first gear is typically low enough to get away with most off-road driving without doing anything else. The NP205 transfer case that is commonly found with the SM465 has crappy low range gearing, and then add a common factory 4.10 axle ratio and you are heavily relying on the low 1st gear on the transmission. You don't have that luxury with a TH350 or TH400 unless you go with a lower geared t-case or axles. For example an SM465, NP205, and 4.10 axles gives you a crawl ratio of almost 54:1. For comparison a TH400, NP205, and 4.10 axles only gives you around 40:1 even factoring in the 2:1 ratio of the converter. 54:1 versus 40:1 is a big difference. Most people I have talked to that dislike an auto for off-roading only have experience with auto equipped rigs that have crappy crawl ratios.......I've talked to several people that have TH400/NP205/stock 4.10 geared axles with 40" tires and talk about how crappy the automatic is....well, yes it will be. Kinda' like taking a Jeep TJ with 3.07 axle gears and putting 37's on it, you just shouldn't expect it to work good.

On my rig the crawl ratio is 34:1 times 2:1 torque converter, so overall around 68:1. That was plenty of gear for 35"-37" tires and works okay for 40" tires but could be lower. Basically I lost the use of 2nd gear in most situations with the larger tires. I do have a set of 5.13 gears that will drop it down to around 85:1 if I ever get around to installing them.

In any case the auto vs. manual debate is personal preference. I prefer auto and will explain why I do, but if somebody likes the manual it's no big deal. There are advantages and disadvantages to both. The biggest thing is that a manual allows you to pull start the rig. Many people will say a manual is more durable but I'm not sure about that....the manual transmissions themselves usually don't fail but I've seen more clutch issues than auto transmission issues on the trail over the years.

07-06-2018, 08:30 AM	#17
blazerbrad - CORE Member - Join Date: Feb 2007 Posts: 831	In regards to the transfer case and differential gearing to make a TH350 or TH400 work it's like anything else in that you need to make sure you have the right gearing in the other components. With a SM465, or other granny geared manual, the first gear is typically low enough to get away with most off-road driving without doing anything else. The NP205 transfer case that is commonly found with the SM465 has crappy low range gearing, and then add a common factory 4.10 axle ratio and you are heavily relying on the low 1st gear on the transmission. You don't have that luxury with a TH350 or TH400 unless you go with a lower geared t-case or axles. For example an SM465, NP205, and 4.10 axles gives you a crawl ratio of almost 54:1. For comparison a TH400, NP205, and 4.10 axles only gives you around 40:1 even factoring in the 2:1 ratio of the converter. 54:1 versus 40:1 is a big difference. Most people I have talked to that dislike an auto for off-roading only have experience with auto equipped rigs that have crappy crawl ratios.......I've talked to several people that have TH400/NP205/stock 4.10 geared axles with 40" tires and talk about how crappy the automatic is....well, yes it will be. Kinda' like taking a Jeep TJ with 3.07 axle gears and putting 37's on it, you just shouldn't expect it to work good. On my rig the crawl ratio is 34:1 times 2:1 torque converter, so overall around 68:1. That was plenty of gear for 35"-37" tires and works okay for 40" tires but could be lower. Basically I lost the use of 2nd gear in most situations with the larger tires. I do have a set of 5.13 gears that will drop it down to around 85:1 if I ever get around to installing them. In any case the auto vs. manual debate is personal preference. I prefer auto and will explain why I do, but if somebody likes the manual it's no big deal. There are advantages and disadvantages to both. The biggest thing is that a manual allows you to pull start the rig. Many people will say a manual is more durable but I'm not sure about that....the manual transmissions themselves usually don't fail but I've seen more clutch issues than auto transmission issues on the trail over the years.