Hi guys
I am trying to figure out what the best trans to put behind a 1997 12valve ... I would like to do a GM bell-housing like the little 4bt , will one of those housings bolt up to 6b ... I would like to run a turbo 400 .
I'm not sure what this motor is going in yet may be a land cruiser or a jeep , but I know I don't want anything electronic .
What are my trans options ... keep in mind I am new to the cummins , I don't know much about dodge transmissions , is a gas trans the same bell-housing as a diesel ...?
Thanks guys
Greg

 

If your going to run an auto get one of from the five big tranny companies on here. My personal preference and who i am a dealer for is Dave Goerend, cant beat his relibility and service. As far as for the 400 turbo, your wasteing your time. These motors pack some power and you would be spending more money trying to get a 400 turbo built to hold the amount of torque these suckers pack. Shoot me a PM if youd like to talk some more.
Luke

 

what he said, except i'm not a goerend dealer. and unfortunately i don't have a goerend converter.
the th400 is a great trans to go behind a built big block but i don't know that you can spend enough money on one to make it handle the low rpm power that these 6 cylinder beasts put out...and if you can, i don't see why you wouldn't want to build a 4spd auto with a lockup converter for the same or less money.

 

I'm curious about this too.

but I don't need an overdrive tranny...this will be going in a rockcrawling rig....very rarely driven fast enough to need overdrive.

 

My professional and personal opinion, don't do it. There is a whole little industry devoted to building the dodge tranny and doing a pretty good job too.

A friend of ours has a Chevy crew cab with a 6BTA from a 1st gen in it. Used the chevy trans with good luck for a few years at near stock power. Gave up the ghost one day and can't get anybody to build it right. One problem after the next, torque converter wasn't built for the right stall speed, shifts weren't firm enough, the list goes on and on.

I told him to get the adaptors for the dodge trans and put the spare one he has in his barn with a different torque converter and valve body.
Enough with the story, on to answer some of your questions.

Yes the bellhousing from a 4B should fit a 6B.

The dodge trans for the diesel and V10 share the same bolt pattern on the case. Some different internal parts, but it should be the same case.
You have:
727 - 3 speed hydralic controlled, no OD, no Lockup
A518 - 4 speed hydralic controlled, electric OD, no lockup
47RH - 4 speed hydralic controlled, electric OD, electric lockup
47RE - same as RH but with electronic controls through the PCM.

 

doesn't the 6bt have a different bell housing pattern than a gas 727 tho ?

 

Well, the 6BT has a bellhousing adaptor bolted to it and the trans bolts to that. But yes there is a 727 for the diesels and a 727 for the gas motors.

 

I was just going to suggest using an old 727...but they beat me too it. They seem to be almost bulletproof with a good convertor in them!

Chris

 

Uhhh...Don't know about bullet proof.

I have had 7 transmissions in my 79 since I got it in 1990. The current one, which I modified (the others were basically stock or with a shift kit), has been working very well for the past 5 yrs or so. She'll chirp 39" tires on the 1-2 shift.

All of the 727's I have are gas models. 2 are SB, and 2 are BB.

Did the first ctd's that had the non OD 727 have a different bolt pattern also ? For some reason, I was thinking the first ctd's (non intercooled ones) had the gas engine bolt pattern, but have not been able to confirm.

 

I went through three 727s in a Grand Wagoneer with an AMC 360 from towing heavy loads. Then I put in a T-18 4-speed and it handled the loads without a problem. I'm no fan of autos, especially for off road or rock crawling. I had my Grand Waggy at angles on rocks that the carbed engine would still run, but the transmission would starve for fluid.

Another thing to think about is that a 6b is HEAVY. I'm cringing just thinking about all that weight coming down off a rock and what would happen to the front axle. Many people use the 4b because they put out a lot of torque, but are MUCH lighter. A TH400 would hold up well behind one of those.

Jim

 

I am not trying to start anything here. IMO GM transmissions are really a lot better they people believe they are. They don't cost much to build to hold the Power. As for the Allison I really don't like them too much, They do feel great when they are built, but talk about some money!!!!!!!

 

True, but when yer looking at rockwell axles, weight is relative.

 

12vchevydually,

I have to agree that the TH400 is one of the best autos ever built. That said, automatics work off line pressure. The pump needs to build enough pressure to make the bands clamp tight enough. The problem is that line pressure builds as RPMs increase. Thats why a well built th400 will work great behind a built big block, even pushing 750+ HP, because higher stall converters are used, and the engines are allowed to rev before hard launches. That builds plenty of line pressure, and the transmission can handle the power at 3000+ RPMs. Gas engines have very little torque at 1000-1500 rpms, but our Cummins' have gobs of torque at 1000 rpms. A Cummins hits redline just as a built gas engine is starting to build the majority of its power.

Jim

 

yeah, I know what you mean about the torque curve of a Cummins. I seen our cummins rip 2 400's up, this is in the stock form and it dosen't take long. I am more into the electronic controlled Transmissions by GM. You can do a lot with line pressure even in the low RPM's.

I do I have to say I love the 727 in my 91. They can take a beatin!!!!!!!!!!!!!!!!

 

wrong wrong wrong the line pressure is controled by a thing called a vacume modulator and NOT by rpm! the trouble is a diesel does not have manafoild vacume like a gas motor so you need to use a vacume pump and a regulator on the throttle. the next trick is to get it set right so the vacume drop will match torque rise. second problem will be shift timming also controled by vacume + govoner. all this can be worked out with time and $$$. the 518 can work without any computer to engage OD all you need is a pressure switch set at what govoner pressure you OD to come on

bill



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