TH400--Steel Transmission Lines VS Flexible

Hey Gents, I currently purchase two 60 inch straight lengths of 5/16" line for my new transmission (Olds TH400 in my dually), and was going to bend them to fit, probably have to re-flare/double-flare one end which is fine as I have the tools.

Then I got to thinking, everything is "in the way" and this is probably going to suck to do-hours worth of time, so I started debating about getting flexible transmission lines. However, the reviews I read are not good enough to make me feel comfortable to buy any.

My question: has anyone had a good experience using flexible transmission lines? If so, what did you use & are you happy with them?

OR--would you say "screw flexible lines" and just spend the time to bend up the metals ones & go?

Thanks!

I always bend new steel ones,just like you were going to do. Sorry,that didn't help at all.

I ran flexible braided (nylon I think) lines on an impala I own and have had good experience but it's a very low use application, and so I can't say much about durability. I purchased a kit with AN fittings and adapters and routed the lines.

@OldBlueDually Justin, just bend 'em and install and save your money for gas........lol

If you went flexible I'd have them made at a place that make hydraulic lines for tractors, semi's, etc. I had to do that on my Jeep back in like 2004 and it's held up. Of course it is the short one that goes from the radiator to the auxiliary cooler, the lines from the trans are steel. On my truck I have the steel lines. If it were my rig I'd bend up the steel lines, much more reliable.

Hey guys, thanks for the input! I always battle myself in my own mind sometimes about this stuff, so I figured just barf it out into words and let you guys give some advice that have actually done this before.

@Ricko1966 it is helpful, if you always do it there is a reason for it!

@Trucksareforwork I plan to run the crap out of this thing, including screwing off aka "pushing it" sometimes, so whatever I do for lines I want it to last. The guy that built the transmission built mine for 550hp and installed heavy stuff into it. He said to "go out and have fun, it'll easily take anything that 455 Olds can dish out"...he started building his own transmissions because he hated other peoples work and not putting attention to important details.

@idahovette You make a very strong case to do what I've already have available to me! Heavens know this baby loves gas....even though I added dual quads on the tunnel ram to try to get double the mileage--holy $h!t was I wrong on that assumption

@DoubleDingo I had read on "the google" that some had done the same thing with success, but that does mean more money also, granted less labor--however, you have sparked another random thought I had (not sure why google didn't spark the thought): Years back my 99 GMC (sierra classic OBS) "had" engine oil cooler lines--my oil pump got stuck wide open (over 80psi of oil pressure) and blew out my oil filter seal on two different oil filters! (enter here an entire book of all things that took place to fix it)-Turns out that old oil line shed rubber, that rubber went into my pump and held it open. I deleted the lines, and put on an old-school 350 oil filter housing with no lines.

Thank you all for the years of experience and advice on this, I think I will just bend up the steel ones! I will sleep better that way, and have one less thing to worry about when I am driving the truck.

Thanks again!

I did braided nylon -6 AN for my 4L65 when I first put my truck together. I just made sure to put some hose over top of them anywhere they might chafe and put clamps every foot or so on the frame and had zero issues for 3 years and 27k miles. That's the only way I'd do trans lines from now on, it was so easy. And I had a healthy cam/converter package and a heavy foot lol

I upgraded my lines to a clutch and third pedal

SquareRoot said:

I upgraded my lines to a clutch and third pedal

Click to expand...

Same lol

TotalyHucked said:

Same lol

Click to expand...

^^^^^ ^^^^^

The trans lines aren’t difficult, they just run along beside the oil pan then bend up to the radiator. Use the small S style clips to keep them together.
The correct flexible lines with the right fittings are probably going to be more expensive than the pre bent lines from LMC…

Reproduction factory cooler lines are pretty cheap. While they aren’t as cheap as bending your own, what’s your time worth?

I used Teflon lined flexible hose on my Olds. If I had to do it over again I’d probably use hydraulic hose.

Whatever you use, just remember the cooler line fittings are NOT tapered pipe thread! The fittings use straight pipe thread with a sealing washer. If you tapered pipe thread you will more than likely crack the case.

Well I got them done tonight, turns out I bought the dark greenish colored copper line, so it bent ok...my bender mildly made a flatter spot than I wanted on a couple bends, and I was able to hand bend some of it also. A few hours of work and had to re-flare the lower one because it was too long.

Overall went well. Hopefully those couple bends won't affect anything....

SquareRoot said:

I upgraded my lines to a clutch and third pedal

Click to expand...

I wanted to do that also, but with the combo I was after a couple of people including my transmission guy said I would've destroyed the transmission due to the torque, and weight of my truck. I really wanted to run a Muncie Rock Crusher 4-speed and Hurst shifter, would've been fun as heck! I found everything to do it too...but I opted not to.