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Need transmission advise - rock crawler

Old June 13th, 2019, 5:40 AM
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Default Need transmission advise - rock crawler

Figured i would put this question in the truck forum. I am building a tube frame rock buggy, 4x4. I need a transmission recommendation. Here is what i have. It has 38 inch tires, 5.37? gears, power plant is a L33 alum block 5.3, stock bottom, 243 heads, valve spring upgrade, brian toolie stage2 cam, fitech fuel injection with vic jr intake. I think i want a manual shift t350 due to its light weight and efficiency. I would like to have the shift pattern p,r,n,123. Need to understand the dif between truck 4x4 trans vs car. Also...i have an old school heavy duty iron transfer case. Wondering about a 4x4 trans where the transfer case bolts right to the end of the trans?
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Old June 13th, 2019, 9:03 AM
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Originally Posted by Dteeter View Post
Figured i would put this question in the truck forum. I am building a tube frame rock buggy, 4x4. I need a transmission recommendation. Here is what i have. It has 38 inch tires, 5.37? gears, power plant is a L33 alum block 5.3, stock bottom, 243 heads, valve spring upgrade, brian toolie stage2 cam, fitech fuel injection with vic jr intake. I think i want a manual shift t350 due to its light weight and efficiency. I would like to have the shift pattern p,r,n,123. Need to understand the dif between truck 4x4 trans vs car. Also...i have an old school heavy duty iron transfer case. Wondering about a 4x4 trans where the transfer case bolts right to the end of the trans?
NP241 should work.
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Old June 13th, 2019, 4:19 PM
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Originally Posted by oilcanhenry View Post
NP241 should work.
Np241 is a transfer case...right? Is the older t350s the same for trucks and cars? I dont have a computer to shift the trans so i want to go old school. From what i know about the t400, they rob more power and they are heavier. Is there a t350 manual shift where the transfer case bolts directly on the end of the trans? Thats kinda what i think i need.
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Old June 14th, 2019, 12:46 AM
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Originally Posted by Dteeter View Post
Np241 is a transfer case...right? Is the older t350s the same for trucks and cars? I dont have a computer to shift the trans so i want to go old school. From what i know about the t400, they rob more power and they are heavier. Is there a t350 manual shift where the transfer case bolts directly on the end of the trans? Thats kinda what i think i need.
Yeah the NP241 is what I have in my 98 K-1500. Its all manual with a floor shifter. Had a Dana-Spicer Model 20 Transfer Case in my old Jeep CJ-5,so yeah I am old-school.
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Old June 14th, 2019, 2:30 AM
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What manual shifting trans will it bolt to? A 98 trans would be controlled by a computer....right?
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Old June 14th, 2019, 8:11 AM
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the th350 is weaker trans (and can be built up) that does require less power to turn, this is why is sought-after by drag cars. the th400 is a stronger trans that does require more power to turn BUT you wont notice the difference when rock crawling.

the other issue youre going to face is the output shaft splines. th400 is 32 and the th350 is 27. the majority of driver side drop trans cases will be 27 splines as thats whats the 700r4 style trans (700r4, 4l60, 4l60e, 4l65e) the 4l80E t cases are 32 splines. you can use a cars transfer case BUT the output shafts on them will be longer 4+" the 4x4 output shafts are only <2". you can cut down some 2wd output shafts but you have to look into that. the th350 2wd can have 3 different lengths ive gathered some measurements on the transmissions and transfer cases
Transmission & Transfer case measurements

the th400 and th350 can be manually shifted and wont hurt them unless you floor it then shift as this builds up line pressure. will this cause it to fail shortly after? no but may cause it to wear faster. you can manually shift them if you dont abuse them and not see any issues. the 700r4 and 4l60 (1983-1993) are not controlled by a tcu, the 4l60E (1993+) and 4L80E (1991+) need a computer. on my 91 V3500 (4L80E) i installed a "black box" which allows me to be able to shift it without no input information from the speed sensors and TPS. only issue is it maxes the line pressure, but since its behind a cummins i dont build the rpms up past 2.5k i dont think it will effect it too much and if it does i need to build the trans up anyway to handle the cummins low end power.
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Old June 14th, 2019, 8:51 AM
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Great info...thanks....making good progress. sounds like i need a np241 transfer case as its manual shift. What trans will it bolt to? Which one of the newer but noncomputer shifted trans will bolt up to a np241and doesnt rob power like a t400? Also....what does it take to make the shift pattern P-R-N-1-2-D?

Here is more info. This buggy i bought with a 496 BBC 14:1 radical motor with a built t400. The output shaft was hooked up directly to the transfer case. 800+ hp was to much for what i want to use it for. Going back to a light 5.3, prob around 400 hp...so...i dont need the big beefy transfer case, figure i can make a lighter weight np241 work. I have low gears...so...figure a th350 style trans would work fine. I need to clarify that when i say "manual shift"...i am referring to noncomputer shift. I want auto shift.

If i want to keep the old transfer case...what trans would work? All the newer trans have the transfer case bolt on right to the end of the trans? What combo do i need?
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Old June 14th, 2019, 11:29 AM
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ok let me ask you this, do you plan on driving this on the road? do you need/want OD? if so you have to go with a 700r4 or 4l60 (not the 4L60E) and they'll be the 27 spline transmissions. if OD isnt a deal then

i cant answer about how to make it that shift pattern.

i dont know what trans you have or what the output shaft splines are, youre going to have to figure that part out. then match that to another trans.
all this being said you can the adapters should relate that style trans and if they dont match up then you can prob buy a used one or new one, the trans you should have should be 27 splines but again you have to check this. if it is then you should be able to use the th350 if you want that trans. again i wouldnt use it i would go with a th400 but then you prob cant use the old transfer case that you have unless you buy a new input shaft.
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Old June 14th, 2019, 12:28 PM
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Thank you for hanging in there with me! I have low gearing, so, OD would come in handy for on the road cruising...even though this is a off road buggy. The rat motor and with the th400 is going into an el camino. So...i dont have a trans figured out yet for the 5.3 in the buggy. I need two options...one that will hook up to the old transfer case and one that has a transfer case (np241) bolted directly to the trans.

The t400 that was in the biggy had an output shaft that hooked directly up with a ujoint to the transfer case. I guess i dont understand why the spline count matters with this option as all i need is an output with a ujoint to make it work? The transfer case doesnt care if its a 27 or 31 spline from how i see it...am i missing something?

I am leaning to just keep the old transfer case as its bullet proof and its all mounted up. Will a old school t350 work from a car or 2 wheel drive truck? Is a 4x4 t350 different? Length isnt a big deal as i will have to remount the motor anyway as the t400 that was in it is longer. If i want OD, then what one would have OD but be small and efficient as a t350...noncomputer?
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Old June 14th, 2019, 1:39 PM
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Originally Posted by Dteeter View Post

The t400 that was in the biggy had an output shaft that hooked directly up with a ujoint to the transfer case. I guess i dont understand why the spline count matters with this option as all i need is an output with a ujoint to make it work? The transfer case doesnt care if its a 27 or 31 spline from how i see it...am i missing something?

I am leaning to just keep the old transfer case as its bullet proof and its all mounted up. Will a old school t350 work from a car or 2 wheel drive truck? Is a 4x4 t350 different? Length isnt a big deal as i will have to remount the motor anyway as the t400 that was in it is longer. If i want OD, then what one would have OD but be small and efficient as a t350...noncomputer?
sounds like youre talking about a divorced transfer case. meaning a driveshaft connects the transfer case to the transmission. the only time the spline count is going to matter is when dealing with a mated transfer case. the divorced ones arnt as common and can be used with a 2wd transmission, so sometimes theyre more practical when dealing with a custom build. cause then you can take the motor/transmission out of a 1 ton 2wd and put it in your buggy and be able to use the OEM computer to control it. my friend who built a truck also matted a 10 speed to his cummins and used a divorced transfer case. this made for a really long front driveshaft and it was in a crew cab so the rear driveshaft wasnt too short.

the 700r4 is pretty much the th350 with OD
the 4l80e is pretty much the th400 with OD
only a few years GM mated the th350 to a np205 (sounds like the "bullet proof" divorced transfer case you have) and that was because they stopped using the NP203 (1979) and didnt start using the np208 till a few years later (1981). till the np208 came out they used the 205 for all 4x4s. thats not saying the np208 is a slouch as GM used it in 1 tons in some applications all other 1 ton applications they used the NP205. The ONLY year GM used the 4l80E and 205 together was in 1991
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