Clanking when shifting into Drive or reverse

I've been having this problem for a long time. Each time I shift into drive or reverse, there is a loud clank. The Jimmy drives fine in forward or reverse, smooth, no unusual noises, but that clank is really bugging me.

I thought it might have been a broken U-joint, but I checked them, they are ok.

Does anyone know what it could be?

you sure they're ok? They don't have to be broken to make a clank... It would be the first thing I would suspect on your symptoms...Check for play, not if they're outright broken.

U-joints need replacing.

Prbably the rear one.

Well I recently removed the rear one and it turned out to be good, however, I only inspected the front one. I'll try taking it apart too, hopefully I find somthing wrong.

When I originally looked at the ujoints, I tried moving the driveshaft for play, but there was little to no play and occassionally when placing the vehicle in drive or reverse, the noise is gone. I am thinking maybe the front one is damaged but occasionally it gets jammed when placed into drive and the noise goes away because I definitely couldn't twist it by hand.

Hopefully this turns out to be a good guess. Thanks for the replies.

Replace the rear joint and don't be cheap.

You had it off, they are only 20 bucks at most.

It ended up being the front one, but I did replace both anyhow.

When I had the rear one off the 1st time, it wasn't a matter of being cheap, I was repairing the differential and simply inspected the u-joint and it looked ok.

The pinion gear and ring gear on the diff destroyed each other. And believe me those 2 gears were anything but cheap! I wanted to replace the entire rear end, figured it might be cheaper, but couldn't find any local scrap yard that had one. Anyhow, the entire job was a success, diff is good and no more noises.

While I was under there, I changed the transmission oil and good Lord was that a difficult task! I had to unbolt the transmission support and raise the tranny to get access to remove and install the pan and new filter. What on earth were they thinking with that design??? Is it the same on your Blazer? I figure it is?

My '98 Jimmy has 1 tranny bolt pan which was tough to get to, being next to the tranny shift linkage bracketry, but I didn't need to play with the tranny X-member. I think I worked that last bolt loose working over the torsion bar, using a box wrench...

I think it's just the 1995 Jimmy LT's, they probably improved the design the years after that. I just find a lot of stuff on it hard to access and work on at times. After all it was the 1st year of the major change to a more rounded vehicle, although I like the boxy style of my 1987 Jimmy and it's bullet proof 2.8L engine and tranny. That one has been a pleasure to work on. Easy access, low cost parts and the parts can be found everywhere and overall a great vehicle! Mine's still running :)