When I shift into 1st and 2nd its fine but when I go into drive it slips like crazy. Maybe related or maybe not I get a clunking sound like its hitting the undercarriage when I floor it from a dead stop. If anyone knows any solutions please help. Thanks.

 

Slipping:

1. Are you shifting it from 1st - 2nd - 3rd (D) like a manual?

2. Are you saying that if you leave it in D and let it shift on its own from 1st thru 3rd that it slips when it shifts into 3rd? IOW, do you have 1st and 2nd in D?

3. If you're letting it shift on its own, does 3rd slip in OD as well? Same thing here and in 2. above; do you have 1st and 2nd when in OD?

4. Also, is the transmission stock or has someone installed a shift kit or done other modifications?

I think you have a worst case scenario on your hands. The 3-4 clutches are most likely fried and your transmission needs to be rebuilt.

Clunking:

The clunking is the transmission downshifting. It's more pronounced if you have a worn or broken transmission mount. The clunking and slipping 3rd gear are not related.

 

1.Yes, I shift like a manual and 1st and 2nd are fine when I shift into D (3rd gear) it slips and it doesn't pull at all and when in OD it slips the same as D.
2. When I am in D it is fine in 1st and 2nd and then when it shifts to 3rd it slips.
3.Yes when it shifts on its own 3rd slips in OD as well and yes I have 1st and 2nd in OD.
4. The transmission is stock and doesn't have any mods added.
Thanks for replying have you ever replaced a 700r4? And if you did how long did it take and how difficult was it?

 

The 3/4 clutch pack is gone, common failure.

The clunking when you floor it is a broken transmission mount. Another common failure.

RBob.

 

Do I have to replace the transmission or just fix the 3/4 clutch pack and the broken transmission mount. Which would be a better choice?

 

In my opinion, it really depends on what your budget is and how long you want it to last (on top of how much power you're pushing). If you're tearing into the transmission, you're better off rebuilding the entire transmission with updated\stronger components to reduce chances of another failure down the road.

If you're running factory power levels, and plan on doing so for the foreseeable future, then you could probably get away with getting a salvage 700R4 and swapping over the tailshaft housing (for the torque arm) or buying a torque arm relocation kit. If you go this route, make sure you get a later model 700R4 as they worked some of the kinks out and you'll need the correct input shaft spline count. With this route, however, there really is no way to guarantee that you don't end up in the same boat next week or ten years from now.

If your budget allows, I would recommend rebuilding the transmission you have, paying special attention to the 3-4 clutch pack. Dana at Pro-Built is a great resource for parts and information.

http://www.700r4l60e.com/

 

thanks a lot for the advice I really appreciate it. I think I am just going to rebuild the transmission or just replace it with another 700r4. How long and difficult would these both be if I did it in my driveway.

 

It's good that you're going to remove and replace the entire unit instead of doing a spot repair on the existing one.

IMO, I wouldn't ever just replace the 3-4 clutch frictions and steels in cases like this. I say this not because it's a band aid (don't get me wrong, I don't think it is if you take the time to do it right). No, it's because this stuff gets EVERYWHERE (in the converter as well):



The labor involved to clean this stuff out of the case and other hard parts is the same whether you just replace the 3-4 clutches or rebuild the entire unit.

I seemed like it took more time to scrub the case and the parts I was going to reuse than it took to R&R and rebuild the thing.