Clunk on Auto Downshift

[346sfi]

This question is regarding my 1988 convertible with 700R4 Tranny. 37,000 original miles on it now, I have owned for just under 9 years and it had 15,000 miles on it when I bought it.

Trans has solid, crisp upshifts and no other apparent issues except the following described "clunks and clanks"

1) When going from nuetral to Drive such as after a long stop light, there is a pronounced "clank" and a jump as the trans re-engages.

2) When slowing to a stop there is a sharp "clunk" heard at the rear of the car when slowed to about 5 MPH. This only happens when the selector is in "D" -- in other words using it as a three speed. The downshift "clunk" does not happen when the selector is in "D" with the square around it -- using it as a 4 speed with "overdrive".

I have checked drive shaft and half shaft u joints and they all seem solid.

Any ideas?

Thanks.

[c4c5specialist]

Hi there,
As for the D down shift condition, that is due to you being IN D, which turns on your overrun clutch inside your transmission, so it doesnt freewheel on decceleration.
As for the clank on acceleration, is it that you are NOT moving and then you hear the noise? If not, is it just that you hear the noise as your starting to move?
Allthebest, c4c5

[346sfi]

Originally Posted by c4c5specialist

Hi there,
As for the D down shift condition, that is due to you being IN D, which turns on your overrun clutch inside your transmission, so it doesnt freewheel on decceleration.

As for the clank on acceleration, is it that you are NOT moving and then you hear the noise? If not, is it just that you hear the noise as your starting to move? Allthebest, c4c5

As for the D down shift condition, that is due to you being IN D, which turns on your overrun clutch inside your transmission, so it doesnt freewheel on decceleration.

DOES THIS DAMAGE ANYTHING OR JUST SOUND BAD? THE TIMES THAT I WANT TO USE "D" ARE LIKE LAST WEEKEND ON A RALLYE ON TWO LANE BACK ROADS, LOTS OF TURNS AND ELEVATION CHANGES. SPEEDS VARY FROM 35 TO 55 MPH SO IN FOURTH GOING UP A GRADE AT 40-45 MPH ITS TURNING 1100 RPMS AND SOUNDS LIKE ITS LUGGING. AN ACCELERATOR DOWNSHIFT WORKS, BUT FEELS BETTER JUST USING "D" TO CRUISE THOSE TYPES OF ROADS -- EXCEPT FOR THE "CLUNK" WHEN COMING TO A STOP!

As for the clank on acceleration, is it that you are NOT moving and then you hear the noise? If not, is it just that you hear the noise as your starting to move?

RIGHT CAR IS NOT MOVING AND I HEAR THE NOISE -- AND FEEL A SLIGHT JERK FORWARD -- THE CLANK IS NOT ON ACCELERATION. IT HAPPENS WHEN PUTTING THE SELECTOR FROM NEUTRAL TO DRIVE WHILE STILL HOLDING THE BRAKE. ONCE ITS "IN GEAR" FROM THERE ON ALL SEEMS GREAT -- NO NOISE WHEN APPLYING POWER AND ACCELERATING, GOOD FIRM SHIFTS, NO SLIPPING. NO NOISE GOING AROUND TURNS, ETC.

THOUGHTS?

THANKS MUCH

[c4c5specialist]

HI there,
Your overrun clutch simply gives you engine compression braking and ALSO more positive engagement of 1st, 2nd and 3rd gear. This is how the transmission was designed and is FINE.
It just sounds bad because your holding everything solid and there is NOT any give.
As for the clunk, it could be just that the driveshaft yoke is releasing and creating the noise, or you just might have a bit of excessive play in the gears within the transmission.
On both counts, it wouldnt really pay to remove the transmission because this could just be a bit of age showing through.
Allthebest, c4c5

[346sfi]

Originally Posted by c4c5specialist

HI there,
Your overrun clutch simply gives you engine compression braking and ALSO more positive engagement of 1st, 2nd and 3rd gear. This is how the transmission was designed and is FINE.
It just sounds bad because your holding everything solid and there is NOT any give.
As for the clunk, it could be just that the driveshaft yoke is releasing and creating the noise, or you just might have a bit of excessive play in the gears within the transmission.
On both counts, it wouldnt really pay to remove the transmission because this could just be a bit of age showing through.
Allthebest, c4c5

Thanks once again for your willingness to share your knowledge with forum members.

Regards,

George