700r4 'clunking' noise: question/opinions

[la_blazer82]

I searched for prior posts and found lots of threads on the 700R, but didn't see anything in particular to my issue.

Whenever I shift into Reverse or Drive, I get a 'clunking' noise, but the tranny seems to shift half decently. There doesn't seem to be any slipping in Drive, except that the shifts are not really smooth. I just bought and towed some new bikes (3 dirtbikes, 1 quad) over the weekend, and now whenever I shift into R or D, the clunking is much louder and I can hear some additional noise like gears engaging.

I recently swapped axles, currently 3.73 on 14bff (am supposed to swap to 4.56 this week), and am running on 35s. New conversion u-joint for rear d-shaft to pinion. I did not change the t-case to shaft u-joint.

Could this be a u-joint problem, or the tranny taking a dump? If tranny, is it better to rebuild, buy one from junk yard, or save up and get a Bowtie?

 

[randy88k5]

Im not the best in diagnosing auto tranny problems by any means, but I would check the basics first. I would make sure your throttle valve cable is adjusted properly. Make sure trans mounts are good. Make sure fluid looks/smells good and is topped off. Check driveline stuff like ujoints. Then start researching internals. I dont have my 700r4 book nearby, so I wouldnt even venture a guess as to internal problems. Hope someone else can help out more.

Also when you tow, make sure your in D and not OD.

 

[1979jimmy350]

check your u-joints they could be causing this

 

[mouse]

What transfer case are you running?

 

[la_blazer82]

Thanks for the tips Randy!

I'm running a 700r4/NP208 combo. I haven't engaged the t-case in at least five months due to the axle swap and the mismatched gears (4.56 up front/3.73 on 14bff - am swapping gears in the next weeks).

I don't have any tranny fluid leaks, no smoking, very slight slipping but this is the original tranny (I think)

 

[vortec]

play in the rear end can also make a similar sound. on a fairly short wheelbase truck, it can be a bit tough to differentiate that from the trans. on my '94 pickup, i was getting a similar sound, a few years ago, but after greasing the slip yoke, it went away completely.

 

[89GMCSuburban]

I second either the slip yoke or backlash in new axle.

 

[la_blazer82]

The problem is that this 'clunking' noise was occurring even before I swapped out the 10 bolt for the 14bff. It just seems to have gotten a bit more porfound recently.

How do you check for backlash? I recently greased every zerk I could find under the Blazer. To grease the slip yoke, do you actually have to remove the d-shaft and grease the slip yoke, or through the grease zerk?