ok thanks in advance to any help

99 d1 140k
noticed a rattle like sound in the floorboard area when i am running around 45 mph to 55 mph cruising speed and when i let off the gas first thought was rear u-joints changed both of them hoping to fix the problem after changing the back drove it and still noticed the same rattling sound. Am i headed in the right place changing the front u-joints next to fix my problem or could i be overlooking something... when hearing that small rattle like sound i do not notice any vibrations in the drivetrain. Once i get up to 60 mph the rattle turns to more of a constant humming sound

frustrated d1 owner

 

Well go ahead and change your front u-joints so that they match the rears in age, some things you always replace in sets, u-joints, tires, brakes...
With the engine off take a small hammer and crawl under the truck and tap on the catalitic convertors, if they rattle, and I am betting that they will, you need new cats.
The are right under the floor board's so I am betting that is the rattling that you hear.

 

ok so as i am ordering u-joints what does code a and another u-joint that has code c,d

 

I do not know what the different codes are.

 

I had a very similar issue. What I did was the following:
[ul][*]Removed the front driveshaft.[*]Locked the CDL, had to do it by hand using an open ended wrench from below.[*]Drove the Disco with power supplied to the rear differential (2WD mode).[*]The humming noise was gone.[*]Ended up rebuilding the front driveshaft using 3 U-joints.[/ul]The U-joints used: MEYLE GERMANY, 514 814 0002, paid $36 for the set.