What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

My father-in-law is nuts....or is he?

3

398HBX

1/2 ton status
Joined
Jul 17, 2010
Posts
161
Reaction score
0
Location
Oak Ridge, TN
Rebuilding a 73 K5, he had a B&M TH350 Competition to go in it. I opted to put a TH400HD, rebuilt with a B&M rebuild kit. He swears that I made the wrong move, that the TH350 Competition is a stronger, better transmission than the Th400HD. I think he's nuts but I need more than just my opinion to sway him. It's too late really anyway, I already sold the TH350, :D. Bottom line, he now wants me to install a 4L60E. I like the idea of overdrive and if I was going to do it, I would go with the 4L80E but I am not sure it's worth it. I might drive my truck 3000 miles in a YEAR, but it would help on long trips. Does anyone know if there is an overdrive kit that can be easily installed on the TH400?
 
Well stock for stock the 400 is stronger than the 350, but the 350 has a slightly deeper first gear and the 350 doesnt eat quite as much power as the 400. My personal opinion is that I would keep to the 400 lineage (th400, 4l80e or 85e) vs the 350 lineage just for the strength aspect.

As for an overdrive to add onto the 400, you are only going to be able to add a gearvendors or ranger overdrive to the back of it. In a K5 I dont think that would be feasible given the length that drivetrain would take on. Also the cost of either of these (new) is over $2k last time I checked, you could buy a 4l85e, the controller & wiring and only be at the cost of the gear vendors unit, and have a shorter combo.
 
With that amount of driving it is going to take many many years to pay for the cost of that 4l80 or 60 in the few MPG you may get because of OD
 
Say 1000 of those are freeway miles were you would be using OD. Say you get an extra 2mpg with OD vs without. That's what 35-40 bucks a year in gas?
 
I say keep the 400 if your not driving a ton of miles......

it is stronger.. but I will point out that MANY drag racers prefer the 350... it's a faster trans across the board... better gear, smaller, lighter rotating assembly spins up quicker, etc....
 
ryoken said:
I say keep the 400 if your not driving a ton of miles......

it is stronger.. but I will point out that MANY drag racers prefer the 350... it's a faster trans across the board... better gear, smaller, lighter rotating assembly spins up quicker, etc....
Click to expand...

I think that is where Stan (Father-in-law) is thinking. He lives in Cali and never took this rig off-road. He is more interested in off-the line performance. I could have kept the TH350 but I put the 3/4T running gear from an 86 K20 under the K5. I wanted the part-time transfer case (208) not the 203. By the time I bought an adapter to mate the 208 to the th350 (different splines I think), it just didn't seem worth it. I have read alot of articles on the TH400HD. It seems like for raw power, the TH400 is just plain bullet proof. As for it taking more HP than a TH350, that may be true, but is there really THAT much difference? I have not been able to find any definitive data on that one.

This K5 is not going to be a serious off road rig, a capable rig, but not for serious rock crawling. Not a daily driver, not a gravel hauler, really just building it as my bugout truck and for the sheer fun of it.
 
it'd be foolish to change from a 400 to a 350 in a truck.. in stock trim, a 400 is WAY more stout... the 350 is better when .010 of sec matters in a 1/4 mile..

the 400 without a doubler, s biggest issue is getting a proper gear that makes your tire size bareable on the highway, without being a pig off the line... but it's certainly doable...

and don't forget, motor, it's power curve and "happy spot" comes into play too...
 
I heard or read somewhere that a TH400 robs up to 20 horsepower just to get moving.
 
yeah, I'm no tranny expert, but it's always been something I heard way back in the day at Englishtown... and it makes sense... I would assume the rotating assmebly is a fair amount larger/heavier....


that being said, I ran a ton of T350's back in my Chevelle's, etc, but coveted any 400 I've had... they're just beef for a street pounder...
 
I's sure as hell not worried about 1/10th of a second on the 1/4 mile. I will NEVER race this rig. As for the rest of the set-up. I have 4.10 gears and plan on putting in a 383 stroker. That should have enough power to use 33 or 35" tires. I have no idea where the power ban will be on the engine, I haven't even started on that project yet. Again, Stan already had bought the parts for the engine, so I guess I'll go with it.:whistle:
 
so with 35's, your looking at 2700 at 65.... what's the induction on the 383 gonna be, carb or EFI?
 
For now, I'm going to use the Holley 650 carb with the Offenhauser intake. I have these in the garage (both new, never installed, bought in the mid 80's by Stan). Eventually, I would like to upgrade to EFI, but you know how these money pits are.....
 
D29096EA7DC266B89C1110FC986EC0.jpg
 
I love that it is all benjamins.
The goverment must be building a really nice blazer.

How about your towing requirments. I have had all incarnations of trannys in my rigs over the years and I seem to constantly be towing. Everything from dirtbikes, boats, job and trashtrailers, to skidsteers and besides my current allison I prefer the 400 for all around use behind my big blocks.

That said I am putting a 350 behind my 350 in the blazer.
 
You must log in or register to reply here.

Latest Posts

Top Bottom