Questions on the 4L80E and 6L80E transmissions

[Woofwagon]

Update, I finally crawled under the beast and found out it's a NP241 case. I've updated my signature accordingly and am researching options for this X-case and 4L80E.

 

[rayra]

If you need a NP 205... why do I suddenly feel like your illicit autopart supplier?

Was his first sample free?

 

[Woofwagon]

Nope.

 

[WilliamKElliott]

One other thing to remember with the 6L80E is that it is an unbelievable large transmission.

 

[Woofwagon]

Yeah, I'm on the hunt for a 4L80E. I'll have so much torque with the Cadillac engine, that I'm not going to need too much gear splitting. I just want one for the overdrive and the toughness of the TH400.

 

[superbuickguy]

As you are aware, I'm installing at 500+ inch Cadillac engine in my '89 Suburban. I have a great Th400 in there now, but would eventually like an overdrive. This leads to a few questions.

1. Is the bellhousing pattern the same between the TH400/4L80E/6L80E? If so that will be awesome as I can get an adapter between the Caddy BOP pattern and the Chevy TH400 pattern for about $60.

2. Transfer case. If and when I go to a 4L or 6L, I will be needing a transfer case with a passenger side drop. I think there is an NP205 on the TH400 now, and I would like to keep it as it's a very strong case from what I've heard. Who makes an adapter between this case and the 4L/6L transmission?

3. Controller. Is it possible or even recommended to run the 4L or 6L without electronic control or is it an electric solenoid transmission? Looking at controller prices made me gulp a bit.

Thanks for any previous experiences you've had on these very strong transmissions.

Woofwagon

1) - yes
2 - it won't fit.... it's a larger 6 bolt pattern... that said, you have another choice that's actually an upgrade - swap in a Dana 60 from a Ford then use the t-case that comes with your 6L80e
3) - no, it won't move without a controller. I know someone who just adapted a 6L60e into an H3, it works well, now... but it took some doing to get it there including a new output shaft

You don't need a 6 speed, really. 6 speeds are excellent for making my 5.3 move the 6000 lbs I haul with me in my H3 - but they are pointless when you have the power and torque to overcome the gear changes. A friend did a 6BT Cummins swap into a late 80s Blazer - he had 3.73 gears, he went down to 3.23 gear because he had plenty of torque but was running balls-flat-out at 60 mph.

Finally, the 205 is great except it has a terrible low range (1.92:1)... to me, that's where I'd spend my money. You can either get a gear Vendors for $2500 to go behind the t-case, or a black box then swap axle ratios to take advantage of the 6:1 ratio you'll have with the black box (or similar).

If you must have extra gears - manual transmission, those don't overheat under high-loads.

 

[Woofwagon]

I crawled under the beast and found out that it has an NP241 case, and not a NP205. I do have the CPU from a 4L80E 454 TBI truck (along with all the other hardware) that should install into the Suburbillac.

I'm with you, I've been thinking of changing gear sets down to 3.43 in the diffs (the highest ratios I could find for the stock pumpkins on this thing). I have a 14 bolt free floater ready for install one of these days. It has 3.73 gears.

I have observed good used 4Ls for sale for around 500 bucks with the passenger side drop xfer cases. IFIRC, the 4L is about a 1.5 inches longer than the TH400 so I'll have to have drive shafts lengthened and shortened.