SC 3800-trans?-dana300

Socsmm6

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Got a Sc 3800 out of a 2004 impala. Trying to figure out what transmission to put behind it. Already have a good dana 300 for the transfer case. I have a th350 in need of a build but it seems the flywheel/torque convertor may be a problem.
904 seems to be the best solution but the one I need is a little hard to find.
Any ideas?
 
transmissionadapters.com

GM401 GM 3800 Series V6 Engine to Chevy Automatic V8 Transmission

Materials Included: (1) Adapter plate - GMC 3800 V6 Series 1 & 2 to Chevy auto(1) Crank Adapter - GMC 3800 V6 Series 1 & 2 to Chevy V8 style automatic(1) Torque converter drive plate(3) FHSCS M12-1.75 X 45 (2) FHSCS M12-1.75 X 60 (1) HEX NUT M12-1.75 (8) SHCS 5/16-18 X 1 3/4 (6) 7/16-20 x 3/4...
transmissionadapters.com transmissionadapters.com
 
I run the L67 > 90* 700R > D300 using the above noted adapter. Alternatively, build a 60* 700R. I had a built/proven 90* 700R and didn't want to risk moving parts over and having oddities.

They have improved the drive plate based on feedback/issues (I cracked two) and the latest version has worked flawlessly. It is now a full 360* round plate, versus triangulated.
 
Did the 60 degree 700r4 ever come with the heavier duty 6 bolt round pattern tail?

I'd be concerned about investing money into the a drive line with adapters to retain a transmission with the 4 bolt pattern.

Only reason I say that is you have an SC3800 so I'm assuming you like the go pedal. I was wanted about mine from my transmission guy when I swapped output shafts and he found out that my S10 has a V8. He warned me to be careful with shock loading it and busting the tail since it is the non-HD case.

Whether or not that is a common issue, I've never personally seen it. But my other trucks have 4L80s with 205s so it's not something I think about with them.
 
The 90* 700r has 4 mount bolts to the adapter.

I had the tail section on mine "finned" to prevent any break-off concerns. Has been like this for over 18 years, zero issues. YES, 18 years ago...the guy I bought my build parts from left that company 19 years ago....replaced the filter and pan when I installed it 3-1/2 years ago in my JHF buggy. 18yo torque converter, 18yo cooler/fan, 18yo internals.

I run an ultra-short Sunray adapter, likely the last one they ever sold. Replaced the output shaft so it matches the D300 input gear, no spud shaft needed.

PXL_20250121_233007763.jpg




I'm an idle/boring driver 99% of the time, but the SC comes in handy for 2nd gear launches. Run a 1" offset SC pulley and a single belt.
 
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If you are going to commit to a 700r4 / TH350 4 bolt style transmission. I would advise to add the fins as Woody said. I broke my TH350 case after a hard hit to the belly.
Trans and tcase was well supported and twisting didn't break the case. I added the fins / ribs like a TH400. It has been great since then.

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l67 - 904 guy here

you are correct, they're not as easy to find these days. mine has been good to me so far.

i rebuilt it myself and if you have mechanical aptitude and a clean place to work i think most anyone can do it as well.

just when you find one, find another... then another and keep them someplace safe 😄
 
RustyC said:
If you are going to commit to a 700r4 / TH350 4 bolt style transmission. I would advise to add the fins as Woody said. I broke my TH350 case after a hard hit to the belly.
Trans and tcase was well supported and twisting didn't break the case. I added the fins / ribs like a TH400. It has been great since then.

20220928_180604.jpg
20221103_183902.jpg
20221103_183852.jpg
20221112_185843.jpg
Click to expand...
What torque convertor are you running? I know the flywheel needs to be redrilled but I have read the torque convertor mounting bolts interfere with the starter. Needs a 10” tc but all I have seen are 10.75 or 11”.
 
worth mentioning.

60deg 904 you'll have to notch the bellhousing for the starter. or go full rock crawler and cut the bottom half off. i run the stock converter, literally the same one i pulled from the junkyard with the trans. redrill the flexplate to match the pattern. plug the vent on the pump and drill/tap the case for the new vent. i also plugged the rear weep hole and seal the tcase mounting flange.

23 spline round pattern, so 300s bolt right up. longer input on the 300 is what i did for better spline engagement and it'll reach the rear seal.

when i was looking id keep the search on 84-86 2.8 cherokees that are being parted out. its uncommon, i know it, but they do show up.... the yj and tj 2.5 30rh is another donor

goodluck on whatever you choose :beer:
 
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Found a jeep transmission but the guy is not sure if its a 904 or a 999. Doesnt the 999 have a different bellhousing bolt pattern?
IMG_5260.jpeg
 
yeah

the 904 you'll need has the 60 degree gm pattern
 
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