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How do I tell which transmission I have....700 or 400?

RNation

RNation

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St.Peters, MO
I have an 84 Suburban, 3/4 ton, rear wheel drive, 6.2 motor. I'm pretty sure the torque converter is about to crap out. I called O'reillys to get a price on a replacement and they need to know which transmission I have. So is there a way to tell by looking at it? Mine has overdrive if that makes a difference. Also, I put a drop in motor in about a year ago, same motor but it was from boyces (something like that) where they take it out of military vehicles. But I had to switch the flywheels to get it to work (flywheel that came with the drop in motor didn't work, so I had to use the one that was on the original motor) so maybe if I knew what transmission the military vehicles had (400 or 700) I could figure mine is the other one. Any ideas?
 
ChevyTrans.jpg
1) Aluminum Powerglide 14 bolts
2) TH200 Metric 11 bolts
3) TH350 13 bolts
4) TH400 13 bolts
5) TH200-4R 16 bolts
6) TH700-R4, 4l60(E) 16 bolts
7) 4L80E 17 bolts

Hope this helps you out! :thumbsup:
 
If your truck has overdrive it's a 700R4. The TH400 was a 3 speed, so there's no overdrive. The shifter display in the gauge cluster would read "P R N OD D 2 1" for a 700R4 and "P R N D 2 1" for a Th400.
 
And if you need a torque converter, I would buy a high quality unit and not a cheapo from O reillys or some parts store like that. Buy a TRANSTAR, SUNCOAST, or PRECISION industries for it and have the trans freshened up with a shift kit so you don't end up having to rebuild the trans in a year and put another torque converter in it.
 
RNation.. Not trying to bounce rocks off your head, but, what makes you think a torque converter is going 'bad'?
 
Well thanks for the replys, so I see I have the 700. I called a local transmission shop yesterday to see about a better quality torque converter. He told me I better bring it in so he can take a look at it to make sure it is the torque converter and not something else. So I'm going to do that.

The reason I'm assuming it's the converter is because whenever I'm driving and I got up to highway speeds the tuck runs a bit ruff (not too bad), and when I let off the gas it feels quite a bit ruff. The part that made me think its the converter is because a friend told me when I'm driving and it feels ruff, to keep the acceleration steady and tap on the break (just enough to make the light come on) and if it goes away it's probably the converter. So I tried that and it it partially worked. It would stop then get ruff again then stop then get ruff again etc. Another reason im thinking its the converter is because I'm not sure what else it could be (unless maybe tranny). It definatly feels like it's behind the motor. Injectors are pretty new so I don't think it'd be a misfire. I also have been hearing a bunch of clinks and clanks in the area of the converter.

So I guess I'm not %100 sure it's the converter, but I'm going to take it to this tranny shop sat and find out. And again thanks for all the info.
 
You could be on the right track then.. I was thinking either 3-4 clutch or forward clutch slippage.

But torque converters have a clutch (700R4) anad they sometimes 'shudder' too. See if the shop checks your trans pressures in all ranges... It could indicate a pump problem. By now the trans probably has some GUNK built up in there, maybe plugging the filter.
 
Could also be broken pump rings causing low pressure and chatter issues as his early trans will have the 7 vane pump in it.
 
Good thing I took it to the transmission shop haha. The guy looked at it and said there was a broken tranny bracket, the piece between the tranny and the drive train (cant remember what it was called, something about a U bolt) was almost gone, and to top it off, there was 4 bolts from the bell housing that were gone! I don't know how they loosened but they were gone. So anyways that solved the issue. The guy described the "ruffness" as a really bad vibration.

Thanks for the information though, as always it's appreciated.
 
Haha....basically yes. I'm not sure how the bolts backed out, that just baffles me. Because I usually over tighten things.
 
Overtightening can cause things to loosen and fall out. Not to say thats what caused it but it can happen. I've overtightened bolts to the point of stripping out the Threads and vibrating back out.
 
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