A friends 1987 has a noticeable clunk from park to drive and reverse etc. On my C3 there is a snubber bushing that is often the culprit if worn out allowing the rear member to shift up/down.

Is there any similar bushings/parts that wear on the C4 that could contribute to the clunking situation? It has about 75K miles and the idle is in the 600-700 RPM range.

Thanks

 

I don't know about snubber bushings but a "clunk" as you describe is an indication of worn U-Joints.

 

The C4 doesn't have a snubber like the C3's did. The C-beam keeps the diff batwing from moving.

 

It could also be worn gears in the differential. Have you checked to make sure it's full of lube?

 

Check the "C" beam's 4 bolts to ensure they are tight. The U joints are likely culprits as well.

Put the car in park or 1st and physically shove the car back and forth (rock it) while listening for the origin of the "clunk".

 

The early transmissions do not have an auxiliary valve body that softens the shifts from park or neutral in to any gear. The 88 and newer have them, and it is an uncomfortable trait of the early units, but none the less, it is there.
I replaced my 86 trans with a 92 firebird trans, and the difference is extremely noticeable everytime I shift from park or neutral after having the car for 13 years with the abrupt shift trait. I still put the brake on hard and brace myself. It will be a habit that is hard to overcome.

 

The later built 1987 Corvettes were built with the Much Improved 700R4 transmission. The one with the Auxillary valvebody to soften shifts between Park, Reverse, and Drive.

My 87 Vert has the Auxillary Valvebody equipped 700R4.

I rebuilt the transmission earlier this year myself and made numerous internal upgrades for increased durability.

My car was built in March of 1987.

 

Thanks for the responses...probably best to get the car on a lift to look it over real good.

Was going to ask if it was possible that the torque converter or tranny itself was acting up. At a stop, you need to somewhat concentrate on keeping the brake pedal depressed or the car pulls away even at idle (600-700 RPM). It's not a launch but noticeable as compared to my 2007 Silverado truck which almost sits in place until I give it some pedal.


I already have them planning on changing the carrier lube, I have extra GM posi additive..any recommendations on a good weight carrier lube.


BTW: coupeguy2001, your description "abrupt shift trait" is a better description of what the car is doing.

Thanks

 

Your 1987 Vette has the K factor Torque Converter of 1397 RPM's or Stall Speed Torque Converter of 1,397 RPM's.

My 1987 Corvette Convertible had the same Factory Torque Converter.
It will creep away forward at Normal Engine Idle speeds with your foot off the brake in Drive Range gear. Nothing to worry about.

During my rebuild, I installed a custom made 2,000 RPM stall with a Heavy Duty Lockup and Full Needle bearings inside.
My car does not creep away any more like the the GM stock Torque Converter Did.

I installed the new torque converter only to gain a little more Snap or Performance off the line. And sure does launch much nicer !

The 1984 - 1986 Corvettes had the factory 2,056 RPM stall speed torque converters.

1987 - 1991 TPI Vettes all had the 1,397 RPM K Factor torque Converters.

The 1987 Corvettes with Auxillary Valvebodys are pretty tough in stock form. Have to run your Corvette pretty hard for several years non stop like I did to make it fail.

The 1987 Auxillary Valvebody Corvette Transmissions have a Shot peened input shaft or Turbine shaft around the Oil Feed Holes from the factory. Non Corvette transmissions dont have this feature.

Corvette only transmissions also had a specially calibrated valvebody and seperator plate.

If during a rebuild, DEFINATLEY DONT LET A TRANSMISSION REBUILDER STEAL THESE PARTS FROM YOU !

THE TRANSMISSION REBUILDERS HIGHLY PRIZE THESE INTERNAL PARTS !!

THEY ARE VERY HARD TO COME BY. NOT AVAILABLE NEW NO MORE.

ONE LONG TIME FRIEND IN TRANSMISSION REPAIR BUSINESS SINCE 1984 TOLD ME THAT THE CORVETTE VALVEBODY AND SEPERATOR PLATE IS HIGHLY PRIZED "GOLD AND DIAMONDS" !! LOL

AND HE TOLD ME THAT FELLOW TRANSMISSION REBUILDERS OFTEN STEAL THE CORVETTE VALVEBODIES AND MATCHING SEPERATOR PLATES FOR THEMSELVES !!! FOR THEIR OWN NON - CORVETTE RACE CARS !!

FROM READING POSTS SILENTLY HERE ALONE ON CORVETTE FORUM OVER THE LAST FEW YEARS, I HAVE TO SAY THAT MANY OWNERS LOST THEIR SPECIAL ORIGINAL VALVEBODIES AND SEPERATOR PLATES FOREVER !

My friend Jeff, is an honest transmission mechanic. Hard to find !

Check Your Driveshaft U-Joints, And Half Shaft U-Joints over closely.

Likely, the One or a couple of the Rear Halfshaft U-joints have failed.

Had to change the Halfshaft U-joints out in my car too.

An easy job if You are handy and can do it at home easily your garage or driveway.

Royal Purple 75-90 W synthetic gear oil, need 2 quarts, and 1 bottle of GM Limited Slip Gear Oil Additive from your local GM Dealership.

Use only the GM Limited slip additive. No subsitutes.

BR

 

Hi BR. How to tell which valve body? I had my 87 (owned since nearly new) rebuilt a few years ago when it started banging into reverse. It has never shifted the same (nice and smooth) since then. The local shop had a great reputation, and after several return visits, convinced me it was the rebuild settling in. 20,000 miles and a few years later, after reading your post, it all makes sense.

 

Read the rules Black LS2. The member you're trying to post to has been banned for some time now.

http://forums.corvetteforum.com/foru...s-or-more.html