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Discussion Starter #1
Hello, new guy here, first post.

I've searched the web, this site as well as others and I'm not finding the definative answer I'm looking for. So here goes.

I have access to a 4BT with a th400 auto trans out of a bread truck. I plan on putting in a project truck that I'm working on. I understand that the th400was a good transmission for the bread truck, but this truck will be 4X4 and therefore it will have transfer case etc, plus I want the 4th gear "OD" that the 4l80e provides. I am also doing this as cheeply as possible so buying a built trasnmission from some internet guru for 4k is not in my budget.

Ok you have the background here is the question. Can it take the TQ from the th400 and mate it to the 4l80e and bolt it up to the 4Bt?

Thank you.
 

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I am new here too but I have a 89 chevy 3500 dually with a 6bt and a 4l80e
with with a compushift computer. I works very well but its not cheap. Exracer2.
 

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Discussion Starter #4
Ok...so what your saying is the TC from or for the 4L80E will bolt in where the TC from the TH400 is with out major modification and lots of addaptors.

Ok that's good to know. Thanks
 

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Been there done that and info above is correct. However, I will add that the 4x4 application is not quite as simple and the 4l80 will not just bolt into place with any tcase. There are several options out there. First you can find the highly sought after, super expensive, 4l80/NP205 adapter and it will bolt up. It is important to note the 4x4 trannies have different length outputs than the 2wd versions and there are a couple of different lengths for the 4x4 depending on year and tcase. The next option is to have a custom adapter built to mate the 205 to the 4wd version of the 4l80; this is what I did. The next thing is to get a late model NP241(think this is right) and use it.
 

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more 4l80e questions

I took the 205 I used on mine. I disassembled the transfercase and redrilled the case to match the trans and then I used a 241 reluctor ring on the output shaft to run my speedometer.
 

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One thing that hasn't been mentioned is the 4L80E is a computer controlled transmission. There is no getting around that short of a manual valve body. The 4L80E is very closely related to the TH400, and uses many of the same hard parts. I've often wondered if the output shaft would interchange...
 

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Discussion Starter #10
When I first posted this thread I asked the question because I have the chance to buy a 4bt with the th400 hooked up to it. I will be putting this into a 4X4 and wanted to use a 700r4 as I have a 700r4 with a transfer case out of another 4x4 truck. But after reading on here it seemed everyone poopooed the 700r4 as a bad transmission, but yet it is used in drag racing so I'm not sure about it being bad. I have since learned that though the 700r4 will bolt to the adaptor I will have to change flex plates and so on to bolt it up. I'm not planning on rock crawling and only light off road so IMHO I think the 700r4 will work just fine.
 

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I just got off the phone with a tc supplier in Minneapolis, MN and he said for me to use the 6.5L tc on my 4bt with the 4l80e. He said he had a forged clutch, 6 bolt pattern converter. It is supposed to be heavier than stock and for higher torque. Does this seem correct? Any help greatly appreciated.
 

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I have been running one for a year and a half now with no issues. Drive it every day and beat the heck out of it.
 

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I just gave up on a suburban with a 4L80E cause it was way to much of a hassle to add the 4bt to it and then spend $1000 on a tranny controller.

In my opinion your better off with the TH400 that came on the engine. I'm wishing really hard I had been able to get the one that came on mine but it was sold already.

You can always gear the truck higher in the axles or add bigger tires for taller gearing. Also over drive units are available for the TH400 as a bolt on at the tail shaft. Also the TH400 can be converted to 4x4 at the tail shaft.

Another possiblity is a 700R4 (overdrive tranny). There is some speculation on these that they are not strong enough but some guys report awesome success with them. There are also trans specialty sites that offer built diesel 700R4's for use in extreme applications ie:rockcrawling ect.

I have a 2wd 700R4 with a police cruiser rebuild on it, the car was wrecked shortly after the rebuild. Funny thing is the car was hit while parked so there was no drive line damage. Its for sale if your interested. The 700R4 is very similar to the TH400, the tail shaft housings are identical.
 
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