I asked this in the Drive line Forum but no answer.
What size steal line do I need to replace the Back Break Line
Thanks

the same size as the stock line lol....i think its 5/16ths or 3/8ths

I was thinking one of those 2 But since I am going to buy a 25' role of it and the Fittings I would Like to get the right size.
Thanks Again

just take the line out of the rear...and take it with you....

i just went to the local napa and said "i need the rear brake line for my truck" and gave him the info. i got one of the longest pieces and i believe a 2 foot piece. I replaced the line from the ABS controller back about 1/2 way right near the fuel tank where it was still good. make sure you coil the line like the lines in the engine compartment. those coils prevent the lines from cracking with movement of the vehicle.

i just replaced all of my back brake lines from the master cyl to the drum and it was 1/4 inch for me.....may be diff on a sub but i wouldnt think gm would use differant lines. hope this helps.

They come in pre fitted & pre-cut lengths from many part stores, got mine at O-Riley's, where is your brake Umm no I mean Break in your brake line :D, also most part stores can provide rubber flex line with adapters, before going to part store; look in glove box RPO list.

Compare it vs the one in FAQ RPO list, to know which brake system you have; it will make part look up easier for them, as different trucks have different braking capability, or as suggested take a piece of the line with you, if you have a rub in the main line there are also compression fitting repair kits for rigid line, cut out the bad & put in a repair coupling if in a straight section of the run.

If possible get a hand vac pump bleeder, I just went thru this a couple of weeks back, took forever using non vac method to get out the air.

http://www.dieselplace.com/forum/showthread.php?t=222675

Brake line at rear I replaced over axle to the wheel cyl flex hose was 3/16" od, (I just measure it to be sure), line into the tee distribution block for left & right side is 1/4" od on a K1500

On my wifes 94 dually C3500 gasser the lines were 5/16. But be careful to save the nuts if possible. The rear 'T' fitting was an oddball thread and not available at several parts stores I tried.

I was able to eliminate all the bad sections with a 2.5 foot piece from rear diff to frame rail where there was a union, and from there forwards with a 5 foot piece where I found good looking tube under drivers door area.

On my wifes 94 dually C3500 gasser the lines were 5/16. But be careful to save the nuts if possible. The rear 'T' fitting was an oddball thread and not available at several parts stores I tried.

I was able to eliminate all the bad sections with a 2.5 foot piece from rear diff to frame rail where there was a union, and from there forwards with a 5 foot piece where I found good looking tube under drivers door area.
That is were Mine is leaking. Right at the connection to the Flex Line. I am a If you are at it keep going. So I will replace from the ABS back. I will do the fuel lines as well since I will be under it and Bending tube any way.
I was holding out until I had the new Exaust and putting it on a hoist for a day.

Thanks for the help