Transmission "upgrade" (downgrade)

[Gaffed]

I purchased a $12 chrome dipstick from the local auto parts store. After I purchased it my brother mentioned that the 700r4 dipstick will work with the th350. I would recommend using it supposing it really will fit the trans. The $12 stick and the stock tbi air cleaner make it weird to get to the dipstick tube. I'm 6'1" and am on my tippy-toes when checking the trans fluid on a stock height truck. Curbs are my friend.


Hey man, I'm just passing the info from when I done my swap a few months ago. Oh and the trans fluid lines are the same too. You might have to bend them slightly but will bolt-up.

 

[Hossbaby50]

I just swapped in a Th400/208 inplace of my 700R4/208. It wasn't very hard. It was pretty much bolt in. Your stock driveshafts will work if you retain the 208 or 241 tcase. Your stock crossmember will work if you retain the same height adapter.

In the 80's GM used the adapter to make up the difference in transmission lengths on trucks with 208's & 241's & possibly some 205's in 1 tons.

Whether your truck has an SM465/208, 700R4/208, Th400/208 your driveshafts are the same length. This is obviously assuming the same application (k5, shortbed, longbed) The only difference is SM465 trucks will have 1350 ujoints in the rear driveshaft instead of a the S44 Ujoints.

The only other difference is the height of the adapters & tcase input spline count. Some are short & some are tall depending on which half of the decade your truck is from. An 87 probably has Short adapters.
700R4 & TH350 = 27 spline 208 (or 241)
SM465 & TH400= 32 spline 208 (or 241)

So if you have a 700R4/208 w/short adapter then you find a Th400/208 with short adapter then you can bolt it in without any major mods.

You might need a flexplate as mentioned. I did not but you might. My tranny lines bolted up, my tcase shifter bolted up, crossmember bolted up, etc. The only other difference is your column shifter won't read the right gear. Also get the dipstick for your new trans as the 700's may not work.

Harley