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SAS 89 Chevy transmission options??

3K views 4 replies 3 participants last post by  Bo185 
#1 ·
Background info:

I have an 89 K1500 shortbed reg cab chevy with a dana 44 out of a 79 f-150 with chevy knuckles and 6 lug outers, ford radius arms plugged into my STOCK transmission crossmember. A 9.5" 14 bolt rear with 6 lugs. 4.88 ring and pinions. Running about 8 inches of suspension lift and 3 inch body lift. 38 mud grapplers. Motor is a fresh rebuilt tbi 350 making about 275hp. Stock IFS front driveshaft and custom rear shaft.

The truck actually has great street manners and is driven on weekends and usually to and from the mud bogs, but I trailer it whenever I can borrow a trailer. Ill be buying a trailer soon...

I recently toasted my 700r4. It was a very expensive upgraded trans a few years ago but only has 40k miles on it. I run the truck 95% in 4 low when in the woods and rarely use 4hi. Also has a giant cooler. Before I had it rebuilt it had already been done twice.

I am at a point now where decisions need to be made...

Is it worth it to rebuilt the transmission a fourth time/swap to another 700r4? OR.... look at manuals? NV3500, NV4500, SM465 etc? OR the 4L80, which I've been hearing great things about, although I am unsure of mating it with my TBI computer setup. I can lengthen my radius arms and move my crossmember back to deal with the longer length of the 4L80. Possibly increase suspension lift and eliminate the body lift to save the current rear shaft, then build a custom front shaft (which i should probably do anyways).

I am not afraid of the manual swap or 4L80 or rebuilding my 700R4, I believe with the right advice and doing my homework I am capable of all of the above options, although i know changing to anything other than my 700R4 will come with a challenge.

Which trans would be the best option all things considered??
 
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#3 · (Edited)
th400.

you have radius arms. and they are tied to a stock crossmember?

rethink.

quickly.

and put the emphasis on THINK.

if you have replaced 4 700r4's, why would you not think of installing something that was stronger, cheaper and better?


sure, the th400 doesnt have the whosamadigits to connect to your computer. you have a vss on the transfer case, right?
 
#4 ·
The crossmember has been greatly beefed up and has been linked to another crossmember i built further forward...but it is in the stock location meaning to change to another length tranny would require a refab. But to solve this issue i would consider it without a doubt. To clarify...i have only done the tranny once since ive owned the truck, the previous owner had done it twice.

How does the strength of the th400 compare to the 4L80? Overdrive would be nice...and if its as strong it would be easier to move the crossmember backward and stretch the radius arms than to move it forward. Im assuming the th400 is shorter?
 
#5 ·
Think of the 4l80 as a th400 with OD basically similar strength wise. With either you have to change the input of your transfercase to 32sp vs your current 27sp. As well as might have to mod driveshafts with a 4l80. The TH400 is pretty close to a 700r4 length wise.

Here the lengths. These show case lengths and 2wd tail shafts.
 
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