Can you confirm I’m right on the 88 delete driveline absorber? (Page 1/2)
Kitskaboodle NOV 29, 07:20 PM
The 88’s (V6’s) do not have the driveline absorber shock. Is this because the last year 2.8 is internally balanced? (i.e. it was no longer needed due to less vibration?)
If I’m correct, I’m curious as to why Pontiac did not do this on the earlier models with the V-6? (85-87)
And yes, I realize the motors came from the Chevy division. (but they could have modified it from the beginning like they did with the 3 piece intake setup)
Kit
Rickady88GT NOV 29, 07:32 PM

quote
Originally posted by Kitskaboodle:

The 88’s (V6’s) do not have the driveline absorber shock. Is this because the last year 2.8 is internally balanced? (i.e. it was no longer needed due to less vibration?)
If I’m correct, I’m curious as to why Pontiac did not do this on the earlier models with the V-6? (85-87)
And yes, I realize the motors came from the Chevy division. (but they could have modified it from the beginning like they did with the 3 piece intake setup)
Kit



I do not know the real answer, but for some reason I think it had more to do with cost than function? GM tried to cut corners and decided that system was not needed? But then, the internal balance does sound viable.
Blacktree NOV 29, 07:49 PM
IIRC the different lower engine mount obviated the driveline shock absorber.

The steering damper is a similar story. The suspension changes obviated that, as well.

[This message has been edited by Blacktree (edited 11-29-2020).]

pmbrunelle NOV 29, 07:55 PM
I view the driveline absorber as an auxliliary dogbone that stiffens with quick rocking movement of the powertrain, such as when the car is launched, or on a hard shift.

Therefore, with the driveline absorber, the normal dogbone doesn't need to be stiff enough to control powertrain rocking from torque spikes; the driveline absorber takes care of those. The normal dogbone can then be made softer, which can transmit less vibration to the car.

Since I have a Rodney Dickman polyurethane-bushed dogbone on my 85 Fiero, I haven't bothered to install the driveline absorber; I don't think it can do much if the powertrain is already well-restrained via the normal dogbone.

I am skeptical to believe:
externally balanced crankshaft: more vibration
internally balanced crankshaft: less vibration

Balanced (however it's accomplished) is supposed to be balanced

Maybe the 88 engines do vibrate less, but I think that would be due to piston mass reduction (discussed in another thread), not due to internal/external balancing. If there is reduced vibration, then the normal dobgone could be bushed with harder rubber, making the driveline absorber unnecessary.

Also pressure to cut costs affects what is judged as necessary or not.
Raydar NOV 29, 08:07 PM
I have 88s. Had several V6s. I also had an 85 GT, that I bought new.
I have yet to figure out what that driveline absorber is for.

(Aside from that... One of our old friends, who was our club mechanic before he passed, replaced that shock with a Kenworth(?) seat shock absorber. Said they were nearly identical.)

[This message has been edited by Raydar (edited 11-29-2020).]

theogre NOV 30, 03:03 AM

quote
Originally posted by pmbrunelle:
I view the driveline absorber as an auxliliary dogbone that stiffens with quick rocking movement of the powertrain, such as when the car is launched, or on a hard shift.

Therefore, with the driveline absorber, the normal dogbone doesn't need to be stiff enough to control powertrain rocking from torque spikes; the driveline absorber takes care of those. The normal dogbone can then be made softer, which can transmit less vibration to the car.

Since I have a Rodney Dickman polyurethane-bushed dogbone on my 85 Fiero, I haven't bothered to install the driveline absorber; I don't think it can do much if the powertrain is already well-restrained via the normal dogbone.

I am skeptical to believe:
externally balanced crankshaft: more vibration
internally balanced crankshaft: less vibration

Balanced (however it's accomplished) is supposed to be balanced

Maybe the 88 engines do vibrate less, but I think that would be due to piston mass reduction (discussed in another thread), not due to internal/external balancing. If there is reduced vibration, then the normal dobgone could be bushed with harder rubber, making the driveline absorber unnecessary.

Also pressure to cut costs affects what is judged as necessary or not.

This is about to completely true.
Second shock is more dog bone keeping engine ripping out engine/trans mounts and nothing to do w/ engine balance. Engine loads up every mount very hard to launch and often to brake or down shift.
GM and others can and does delete anything to cut inventory, build and other costs.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

[This message has been edited by theogre (edited 11-30-2020).]

fierofool NOV 30, 10:28 AM
Isn't the front crossmember located differently on the 88 as to prior years?
theogre NOV 30, 02:06 PM

quote
Originally posted by fierofool:
Isn't the front crossmember located differently on the 88 as to prior years?

Don't remember but likely not relevant. GM could use same shock mounted different or another shock type or simple "dog bone" type w/ different mount points on 88's but GM didn't bother.

Front engine/trans mounts w/ transverse drivetrains can have same problem as left mounts w/ front engine RWD vehicles breaking to launch etc.
Many OE mounts not just GM parts are very cheap and break easy. Is why many replacement are made to resist tear outs.
Old GM Fords RWD have problems and good replacement had changes to stop this in several ways. End Result new mounts had a "chain" to limit mount loads. Same thing many people use Actual small chain or cable across mounts to do same.

Even w/ better mount design, some still use chain/cable because better mounts aren't made to take abuse for drag racing etc.
Many use chain wrap in old hose to stop noise driving normal allowing mounts to work.
Cables are used by OEM for same reason. Cables are easy to make to meet spec and have no noise when not needed. You don't see this used very often. I only seen them a few times in decades of fixing cars and trucks.

Engine "Shocks" and "Dog bones" for FWD and Fiero try to do same job... But...
Dog bones in Fiero and some others have problems because mounted at one end allowing drive train and more importantly 84-87 Fiero cradle to twist and steer the car. (See my Cave, Bump Steer)
85-87 V6 Engine Shock tries to limit that but doesn't help much. I think Is mainly to act as chain across front mounts. Unlike suspension shocks, these are made to handle hitting end of travel more but can still break or leak. 30+ years later many have problems.
hyperv6 NOV 30, 05:43 PM
The shock was used on t be early cars just to dampen the movement of the engine under acceleration.

This makes for a smoother transition and helps prevent damage to the mounts.

The V6 is an even fire 60 degree engine so vibration or shake is not a problem like it is on the 90 degree 3800 V6. The 60 degree cylinder banks are naturally smooth and is why most modern 3ngines like the 3.6 are 60 degree. Also they fit tighter engine compartm3nts.

Yes the 88 has a different cross member as the entire front suspension was redesigned. They bolt in the same but are different geometry and a different design.

As for the cars with cables and chains to limit engine movement.

The cables GM used were due to a recall for bad mounts. If the mount broke the engine could flop over and pull the accelerator cable. I had this happen on a 1960 Bonneville. It took off to 60 mph with out touching the gas. What made it more fun was the car lacked power brakes and steering too.

GM used the cable and clamp to limit the engine if the mount broke. Today they use interlinked mounts so if they fail the catch to prevent a run away car.

Chains were used by folks who did not want to spring for solid mounts in racing. It works but solid mounts are cheap.

Many new vehicles are using hydraulic mounds today to dampen any vibration out of the drive line as it is firm but eats the vibration to make things even smoother in today’s cars.


As for the 88 missing the strut. GM may have eliminated it as it was really not needed. GM often eliminates things that while they work they can live with out.

My ZQ8 Sonoma had a horizontal Bilstien strut as a traction damper. GM after a year or so eliminated it. It worked but few knew it was there or even knew what it did. Cost savings at its best.

[This message has been edited by hyperv6 (edited 11-30-2020).]

Toddster DEC 14, 08:16 PM
Kit, I actually like to retrofit the shock on the 88. It is one of the few things GM reverted on instead of improving on. When they removed the U shaped front engine bracket in favor of the L shaped braket, they put a lot more stress on the bracket, the front mount and the dog bone. I have literally seen several cracked L brackets due to this problem.

I weld extra steel into the L bracket, run a through bolt in the front mount with poly bushings on either end, and poly dog bone bushings and then retro the shock whenever I build-up the engine to 3.1-3.4 liters.