ZR-1 Maintenance Tips

General Maintenance

by Jim VanDorn

 

The most common call we receive by far is from a confused ZR1 owner. After years of reading everything from which thermostat to use, to what type of spark plug is best, the average owner is totally and completely confused...and for good reason. There are many varied opinions of what is best for our cars but that may depend greatly on how you use your ZR1.

 

After seven years plus, many ZR1's are finally accruing some mileage. We have had the opportunity to closely inspect many engines with a variety of types of use from normal street driving to severe "weekend" use (track time). Compiling this information we can now offer the ZR1 owner some observations. One rule we've adopted after hearing so many owners say the same thing is the "DIMWIT" or "Darn, if I didn't Mess With IT" rule. In other words, if you didn't have a problem, then what are your intentions in the first place? To date, the only company known to have a fleet of engineering ZR1's to test with was GM and it's affiliates.

 

Therefore, we must ask ourselves if their suggested procedures and parts recommendations should have a considerable amount of merit. Obviously they do, but on the other hand, there are no doubt areas for improvement. Although we will begin our segment discussing the routine and normal maintenance of the ZR1, there are many areas where an upgrade will be suggested.

 

Please understand that these are personal opinions and experiences and are not intended to conflict with service procedures outlined in the appropriate service manual.


  Articles
One area where large mistakes are made regarding the LT5 is in the clutch/flywheel department. The LT5's clutch has an approximate service life of 40,000-50,000 miles but this varies greatly depending on the type of usage. No doubt some owners can get more and there are those who can claim half (or less) of that.


When servicing a clutch assembly, most technicians will see the flywheel's dark spotted appearance and immediately suggest re-surfacing the flywheel. DO NOT allow this to be done. As warned against in the service manual, the dual mass flywheel must not be surfaced. This appearance really does not reduce the clutch's effectiveness or hamper it's operation. Unless you have felt some previous vibration, noise or other problem, leave the flywheel undisturbed. Your flywheel, if original, was balanced with your engine, therefore, a replacement will not be as accurately balanced (see "Other Flywheel Concerns" below). If there are visible groove, etc., on the flywheel, then there is no choice but to replace the unit with a new one available from your dealer for approximately $800.


Also important in the clutch area is the replacement of the throwout bearing and pilot bushing. Do not panic if the pilot bushing is loose within the crankshaft. This is common and a source for many loud clutch related noises. If ignored, the loose bushing may enlarge the crankshaft hole so excessively, the newer bushing will not seat. This will be cause for some creative machine work.


There has been much confusion over which bushing is to be used. GM has changed their part numbers several times and are currently referring to the bearing (part #14061685) to be used. We strongly suggest NOT using this bearing as it is a needle type bearing designed for 6.2L diesel trucks which have a limit of only 4,000-4,500 rpms. You can imagine how fast those little needles will turn at over 7,000 rpms. We have seen some failures which were quite interesting. The ideal bushing replacement is a bronze type with three grooves (or flutes) spiraled inside and is available under the GM part number 10125896.


Special Note: Some of you may have had the occasion to replace a pilot bushing on engines other than the LT5 by filling the hole with grease and then using a punch to force the bearing out by the hydraulic method. This will cause major problems if done on the LT5 as it is a hollow crankshaft with a plug seated at the end. Carefully use the appropriate tools for removal and installation of the LT5 pilot bushing.

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