I've had a question that I'm sure is a stupid question burning in my head for months and have searched the forum and google and anything else I can think of to try to avoid having to ask. But alas, I was not meant to find the answer. So here I go.... We all know about 4-hi and 4-lo. Now is that the same as a dual transfer case? If yes, great. If no, can someone please explain the difference? I'm glad there's a Newbie section so you all expect stupid questions. That way you're ready for the shock....

 

Not really. A transfer case has two components. The main part is the gearing and shifting mechanism to "transfer" torque to the rear and/or front driveshafts. Then there is the reduction gear box up front that has high and low range. The term "dual case" is sort of a misnomer. It is true that you start with two transfer cases, but you take one and keep it intact, but you take the 2ndd one and remove the reduction gear box (discarding the rear front/rear drive part) and stick that reduction box between the transmission and original transfer case. So technically it could be called a "transfer case and a half". But what does that give you? High and low range in the front box, high and low range in the rear box and 2WD/4WD in the rear drive section, so you end up with high-high, high-low, low-high and low-low gearing plus 2WD-4WD. In compound gearing, you multiply the two gear ratios (high is typically 1:1).

 

You're a genteman and scholar! Thanks so much. That's the most straight-forward answer I could have imagined.

 

i have a question myself...dual t case options for my 85 sr5 runner. would i need a 21 or 23 spline case?? other than the obvious spline count, what is different???

thanks

 

Standard spline count is 21 on inputs and outputs. If you are building duals you can increase the spline count between the two cases to 23 spline for added strength if doing tcase gears at the same time. That's the short version.