Transmission I.d.

[BIGPIMP]

guys i've got an 81 chevy pickup with a 350 engine .ok my trans went out and i have a chance at 2 pretty good trans . 1st my trans that i'm taking out ,i think is a 350 .it has a 2 prong plug on the drivers side . now one of the trans that i can purchase has a 4 prong plug and the other doesn't have a plug at all . now my question is i think that the 4 prong plug is probably the closest to my original so how can i convert my 2 prong to the 4 prong ? thanks

[Slonaker]

You really need to find out what type of transmissions they all are and go from there. If you don't put the same type back in, you may have to move your crossmember and shorten or lengthen your driveshaft. It isn't just as simple as matching the plugs.

Slonaker

EDIT: http://www.nastyz28.com/transid.html

[edman87]

your trans is a th350 or th400, don't know of any other tran in an 81. With it a half ton it is almost certainly a th350. Look at the pan and compare it to the prospective buys. If it is the same- exact same shapr, 3 of bolts etc it could be the right trans. What are the other transmissions in? Post the pan shape here an someone can tell you for sure.

[BIGPIMP]

Originally Posted by edman87

your trans is a th350 or th400, don't know of any other tran in an 81. With it a half ton it is almost certainly a th350. Look at the pan and compare it to the prospective buys. If it is the same- exact same shapr, 3 of bolts etc it could be the right trans. What are the other transmissions in? Post the pan shape here an someone can tell you for sure.

yes the pan shape is the 350 and as far as the driveshaft the tail lenght is the same ,my worry is that my original trans has that 2 prong plug on the side and the one that i want to put back has a 4 prong plug . the question is how do you deal with the plugs .do they make an adapter to connect them ?

[edman87]

I havn't dealt with old automatics in a while, but what does the plug do? There is no lockup or electronics, should just be a reverse indicater right? Don't the plug screw out like a sending unit? IIRC, you can just swap the "sending unit". Like I said, I havn't messed with an auto or a th350 in a long time, but don't remember any plug on them other than a reverse indicator.

[trkklr77]

the 4 prong should be a newer one wit a lock up converter. dont know how to change it around though.

[BIGPIMP]

Originally Posted by edman87

I havn't dealt with old automatics in a while, but what does the plug do? There is no lockup or electronics, should just be a reverse indicater right? Don't the plug screw out like a sending unit? IIRC, you can just swap the "sending unit". Like I said, I havn't messed with an auto or a th350 in a long time, but don't remember any plug on them other than a reverse indicator.

after taking off the pan that switch run thru the inside to what looks like a sending unit . wonder what would happen if i don't use the plug . you know run the trans without the plug ,plugged in ?

[drillingmachine]

did you pick up a pontiac tranny? don't know why the plug would be any different.

[84 400]

it can't be a lock up (right guys and gals) cause it is a th350. Unless u mean somthing else beside lock up torgue converter. that was only in the 700r4's and the pan is totaly diffrent. unless u mean somthing else by lock up.

[82c10]

Originally Posted by 84 400

it can't be a lock up (right guys and gals) cause it is a th350. Unless u mean somthing else beside lock up torgue converter. that was only in the 700r4's and the pan is totaly diffrent. unless u mean somthing else by lock up.

no, the lockup torque convertors were used on later turbo 350's , and i believe the four prong plug is the one with the lockup torque convertor, if i was you i wouldn't get that one (from a performance standpoint). they say you can get better gas mileage with the lockup, but you can't buy any performance torque convetors (higher stall) for the lockup ones with a reasonable price, also i believe on the mainshaft( i believe) also has a seal, that the non-lockup shouldn't have

[BIGPIMP]

so is it gonna make a difference if i don't plug anything into the tranny ,like don't use the plug ? the tranny won't cost me much and i can depend on the guy selling it to me . so can i use it without using the plug ,will it work properly without the plug ?

[krazymonkeys24]

as far as th-350's are concerned, the only thing you should be worried about is lockup or non lockup, since in a non lockup truck, you won't be using the lockup converter and if i am not mistaken, they have a different pump pushing different pressures. tailshaft length, but you said that is the same. Definitely replacing your modulator valve and your front and real seals. It's easier to do it on the table at your leisure than to have to crawl under it and bust your knuckles on everything when you pull the retainer for the modulator. They don't cost much ($12 for the modulator and $3-4 for each seal) and it's always great to know it's not going to be a bad one once it's in. Also, when you replace the front seal, MAKE SURE that you take a good look at the pump gear, which will be behind the seal. All you will see of it is the two tabs that fit into the end of the converter, but chances are that if you have a busted pump, those tabs won't be there. The torque converter will twist those off as soon as it locks. i had that happen recently and didn't realize it until I got a mile down the road and my tranny locked.


Edit: Also, the plug won't make much difference. The vacuum going to your modulator will control your shifts, so that won't be much of a prob if it's unhooked.