When I drop my car in gear the whole car does one big bump

So like... 1st... shift 2nd BUMP zoom zoom baby shift 3rd BUMP etc.

I've been told that this is bad u-joints on my driveshaft... how can I tell for sure?

Thanks,
iSP33D-for-J3SUS

 

Worn U-joints go "tink" just as you start rolling, then sometimes rumble or vibrate at different speeds.

A "thunk" when you change gears is usually the front differential mount.
The torque change on the differential causes it to push up the pinion end to hit the floor.

The RX-7 sound dictionary:
Thunk (when starting out & changing gears) - Front diff mount.
Tink (when starting out) - u-joints
Clunks or groans (with suspension movement) - old grommets.
Zoom zoom (short cycle) - vac leak
Zoom zoom (long cycle) - TPS or BAC or grounds
Crunch - high rev shift to 2nd
Beeeeeeee - over rev or low coolant or low oil.
RrRrRrRrR – all even compression surges in the starter gear noise (normal)
rrrrrrrrrrrr - no compression surges (flooded)
RrRrRrrrRrrrR - uneven compression surges (2 of 6) (bad apex seal)
RrrrRrrrRrrr – alternating strong & weak surges (low compression on one rotor)

 

Rockforddriveline.com. Two new U-joints, $50bux plus shipping. The Guy that answers "nos bout joo" just tell him its an RX7 and he'll know just which u-joints you need. Then you need to spend a Weekend fixin' for yourself.

 

Actually I have the same problem right now, it is the diff. mount. If you go out to your car and you see the diff, where the driveshaft meshes in, if you can push this part up you will hear the sound that your car is making. 99.9% certain this is your problem.

How much will it cost to replace?!?! does anyone know. I'm curious myself.

 

That's good to remember

 

When my driveshaft was taken to a shop we found the u-joints were non-replacable and you to customize the shaft for proper u-joints? Because that's what I had to do.

Hammons, have you done it yet yourself?

 

yah I thought they were non replacable, sure look like it.

 

I just got the u-joints for my TII from Rockford driveline today, and will put them in Saturday. I guess I'll take some pictures of the procedure and post them.

Basically, you grind off the staking, press out the old, then press in the new joints. Instead of staking, the new joints are held in by 4 cirlips at the bases of the u-joint caps (you don't need to cut a groove, but you may have to radius the yokes just a tad to make room for the circlip).

Part numbers are 430-10A for the normally aspirated, and 430-11 for the TII. They come with the circlips, a grease fitting, and instructions. The cost for the TII joints was $22.40 each, + $10 shipping, for a total of $54.80. I received them less than a week after ordering them.

Like I said, I'll put them in this weekend, and report the results, but this has all been done before, by other members of this forum.

 

oh I know what you're doing, you got a whole new yolk.

 

Huh-uh. Just the joints. I'll use a Dremel to grind the staking down in the yoke, so that the old joints will press out.

Edit: I'll take before AND after pictures, so that all will be clear.

 

archive the RX-7 sound dictionary!! Good to have info lol!

 

When I removed my front diff mount, it separated into two pieces, the rubber was completely annihilated.

 

[quote=buttsjim]Part numbers are 430-10A for the normally aspirated, and 430-11 for the TII. They come with the circlips, a grease fitting, and instructions. The cost for the TII joints was $22.40 each, + $10 shipping, for a total of $54.80. I received them less than a week after ordering them.[q/quote]
Buttsjim is exactly right.......just what I said 55 bux for the two u-joints. You can also aorder the EXACT same part numbers from a place called Arizonadriveline.com if you are on the West Coast.

Yes jager, I have the u-joints in my car right now. It took a good day to beat out the old rusty joints and put in the new ones but it was better than a new drive shaft from Mazda at $350 bux. Just remember the New u-joints have the pin on the inside of the yolk so you really can dremmil the **** out of the outside fo your yould to get the old joints out. I was really worried about it and I dremmiled too conservativley. After looking at the new u-joints when they were in place.....they didn't even come close to the area where you have to drimmel....the "Staked" areas.

One recommendation that I would make, take the shaft in and have it balanced before you put it back in. Go to a Deisel shop or Machine shop

Ok Two recommendations, There are balanced Washers on the rear yolk. When you are taking the drive shaft out Mark which hole the washers came out of. Kepp the nuts/bolts/washers together and remember which hole they came from.

Ok, three recommendations, buy a rear main oil seal before you pull the driveshaft out. Replace it while your under there.

4) While your there check the Speedo cable and tranny for leaks and fix them while you have all the exhaust heat sheilds removed.

5) Make sure you have the ability to get the car up high enough to work under there. Ramps won't do it. But the $25 jack with four stands at Kragen will. Jack that car up on all four corners, as high as you can....especially if your fat like me.

 

You don't need a whole new yolk, just u-joints. It's easy

 

Differential? Did I miss something?