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OP - I believe the ML9/GT7 quite rare and actually it's generally thought that most '89 ML9 would be a 3.54 build (GH0). A 3.07 only in the A4 builds never with the M6.
** I actually believe that there was a production change and all production for '89 changed to GT7 maybe around FEB 1, a build of earlier than FEB/89 might make the GT7 very unique.
Here is my RPO list for a June of 89 Z51. It has GT7 and the MN6.
I'm new to vettes, GT7 is the 3.33 rear? Anything else interesting in my RPO's? i know its a high option car but not sure if there was anything unusual.
Here is my RPO list for a June of 89 Z51. It has GT7 and the MN6.
I'm new to vettes, GT7 is the 3.33 rear? Anything else interesting in my RPO's? i know its a high option car but not sure if there was anything unusual.
Yours is very similar to mine, but I see you got the (AQ9) sport seats, (D74) illuminated driver vanity mirror, (FX3) select ride control, and (UJ6) tire pressure monitor system. Very cool! Your build serial, last 5 digits make it a later year build. I am pretty sure ours were made well into the model year. I found a 1989 spec book online with the GT7 and G87 penciled in. Must have been a late incorporated change that published books didn't capture in time. You will notice this with other sites with 1989 corvette specs and no mention of the two codes.
Enjoy your ride and maybe I'll catch up with you at the next Carlisle show.
A couple minutes with a torch and all the old studs are out! Funny how I tried using PB Blaster on the driver side and broke all three studs. I said hell with it on the passenger side and one stud unthreaded and the nuts came off on the remaining two.
Placed my order for the remaining needs with Autozoo while they had there great 20% off with free delivery. Here is the list...
Rear brake kit
Belt tensioner
Belt
Water pump
Lower hose
Upper hose
Throttle body coolant hose
Thermostat OE
Thermostat Gasket
Clutch set
Fuel rail o-ring kit
Spark Plugs AC Delco 41-627
Spark plug wires
Oxygen Sensor
Air Filter
Radiator
Radiator cap
PCV
Tried to order rotors, but front driver side was not available. J55 uses directional rotors due to the vanes casted into the rotors. My plan is to order a set of EBC rotors and get Yellow Pads. We run these in our Lemons Chevette and they are outstanding on the road course. Read a couple of reviews due to cold operation compromise, but feedback was that there is no difference than OE pads cold. When they heat up is where the fun begins. Same applies to tires.
Have two headlight bushing repair kits enroute due to driver side lamp over running at each position. Another great info find on the forum. Also have a new gas fill boot on the way too due to mine cracking upon removal.
Going to introduce myself to my local dealership for the gas cap, ZF specific transmission fluid, and exhaust manifold studs.
The passenger side runner and new oil cooler tube arrived. I really did a bang up on that tube when the engine finally let go. Here is a picture of both old and new.
Hopefully engine is ready for install this week, and just in time for single digit weather. With the engine in I can roll it into the garage for the remainder of the work and have heat.
Still looking for feedback if I can drop in the engine with heads installed, and where to mount chains for the cherry picker.
I still have to find my old repair manual which I need it for torque specs and sequences.
Found the manual, are 60 for short and 65 for medium and long head bolts still applicable?
Last edited by mcguirjf; 01-03-2016 at 05:43 PM.
Reason: Add picture and found manual
Going to introduce myself to my local dealership for the gas cap, ZF specific transmission fluid, and exhaust manifold studs.
It's unlikely that the dealer will have the ZF Fluid (GM# 1052931), if the dealer doesn't have the correct fluid buy NOTHING from them. Their most likely offered choice is NOT correct. They don't have a valid offering.
The debate over which and of course "the best" has gone on for years. There are multiple threads here on the CF for ZF lubricants. I won't suggest one over the other but just suggest a search. I have OE/GM for probably as long as I need.
Use the OE/GM# as a reference for what ever you buy. Many have a correct reference but it's not what they offer sometimes when asked.
Found this on ZFDocs website - Check the FAQ section for the full write up. it sounds pretty conclusive.
A.) Jim, the C4 Corvette ZF S6-40 6-speed transmission uses engine oil for lubrication. I was told by Jeff Henning, Warranty Administrator of ZF Industries North America, that Engineering of ZF Industries in Germany determined that the BMW imported Castrol (RS superseded by TWS) 10W-60 oil was the recommended alternative to the (GM P/N 1052931) factory-fill oil for use in the ZF S6-40 transmission. In effort to verify ZF Industries alternative lubricant recommendation, we ran our own test series on the BMW imported Castrol TWS 10W-60 oil. Independent testing of the transmission oil samples was sub-contracted out to CTC Analytical Services.
I am going to the dealership tomorrow to verify this is true. I am also going to stop by a few other dealerships too.
Please let me know if this is correct.
What they sold you is NOT correct and rater than argue with them just return it. I know of no present lubricant that GM has that is spec'd for the ZF. I'd run synthetic engine oil before I'd do either of their products that you've mentioned.
If you like NAPA they likely have Royal Purple:
If you walk in and ask they'll offer you up their product they normally sell but if you use the RP guide (take a look) for the GM # I mentioned and see what they reference:
Not to make this adventure anymore boring, come to find out the exhaust manifold bolts (qty:6) are discontinued and the only close offering was $10 each! Hahaha. The parts guy even stated that it was ridiculous. Going to have to search hardware store for correct studs.
On a plus note, my gas tank boot arrived and my two headlight rebuild kits. Will post pictures and results.
Not to make this adventure anymore boring, come to find out the exhaust manifold bolts (qty:6) are discontinued and the only close offering was $10 each! Hahaha. The parts guy even stated that it was ridiculous. Going to have to search hardware store for correct studs.
On a plus note, my gas tank boot arrived and my two headlight rebuild kits. Will post pictures and results.
I believe there's only a couple mm difference from OE to the Dorman 675-576. That should be everywhere. Take your old to match. If you have one there what's the length of the short and the long? Overall?
The GM is worth a "premium price" just because of the finish. The price that you were quoted?
2.23 overall length
.425 length engages manifold
1.21 thread length for nut engagement
.325 length no threads with OD of .275
Thread max OD .375
Thread min OD .332
Thread count 1.5
.250 length with no threads at .375 OD at mid span
All units in inches
Coil had a cover for Performance Distributors made in Memphis, TN. The DANGER HIGH VOLTAGE label is pretty cool. It must add at least 5 HP!
Got 3 of 4 bolts removed and of course broke one.
Contacts not bad, but might as well change out the cap and rotor while accessible.
If the cap and rotor were a "premium product" they could be and likely are better than anything or most that are available today. I'd maybe rethink that and look again. Maybe a new "brush" for the cap?
Just talked with Performance Distributors and cap and rotor replacement will not impact performance. I was off on my sticker 5HP estimate. Per the manufacturer's website 15-20HP with possibility of 40HP.
A: It is hard to say exactly how much the DUI will increase horsepower. Too many parameters are involved to answer this question with an exact answer. On average, the DUI will produce an increase of 15-20 horsepower over a stock ignition system. Your engine may see more or less depending on other modifications. The DUI has been dyno tested to provide 40 more horsepower over a stock GM HEI! Unfortunately, we cannot guarantee this type of result for everyone. But in most every case, the DUI will provide a noticeable increase in performance and fuel mileage.
Just talked with Performance Distributors and cap and rotor replacement will not impact performance. I was off on my sticker 5HP estimate. Per the manufacturer's website 15-20HP with possibility of 40HP.
A: It is hard to say exactly how much the DUI will increase horsepower. Too many parameters are involved to answer this question with an exact answer. On average, the DUI will produce an increase of 15-20 horsepower over a stock ignition system. Your engine may see more or less depending on other modifications. The DUI has been dyno tested to provide 40 more horsepower over a stock GM HEI! Unfortunately, we cannot guarantee this type of result for everyone. But in most every case, the DUI will provide a noticeable increase in performance and fuel mileage.
And if your purchased new cap and rotor aren't of equal construction as to what's there you expect maybe a 12 HP loss? LOL
PD commented I guess regarding using "their product" vs. SungHuJin's performance cap and rotor sold by most but constructed in China?
And if your purchased new cap and rotor aren't of equal construction as to what's there you expect maybe a 12 HP loss? LOL
PD commented I guess regarding using "their product" vs. SungHuJin's performance cap and rotor sold by most but constructed in China?
My 1989 C4 has a DUI distributor in it. It was on there when I got it so I can't comment on any improvement it may have made over stock. The main claim to HP increase of the DUI is the uprated coil and module which produces a higher voltage than a stock HEI coil. While this may allow you a slightly higher RPM operating range without other supporting mods (1.6 ratio rocker arms and/or a cam for example) I can't see it giving you a lot of HP increase over a stock HEI. They also claim their distributor body is more precisely built and their centrifugal and vacuum advance are better tuned for more power as well. If there is any improvement I'd suspect that is primarily where it comes from. I don't know how much either of those things really plays in on an ECM controlled system like a TPI though.
There is nothing that special about Performance Distributors' cap as far as performance goes other than it was a good quality one. Any other good quality cap should give the same results.
The main difference in quality of caps is in my opinion defined by 2 areas... quality of the materials and workmanship of the contacts is #1 by far. The material and coatings on the contacts makes a difference in how well they conduct and how resistant they are to corrosion. Second is the materials and workmanship (mainly precision) of the cap body itself. The material of the cap mainly makes a difference in how well the cap will hold up under high RPM use, how insulative it is and how well it holds up under heat. I would suspect that a cheap cap may work fine for a while but probably won't last as long.
Hi Jim,
You can use a full synthetic synchromesh lubricant or BMW P/N 832122365944
in the ZF S6-40 transmission.
You can change oil cold. Refill till oil dribbles back out the fill hole,
about 2.1 liters (2.2 qts).
The clutch system is comprised of the clutch assembly and the clutch release
system (clutch hydraulic system).
If the clutch isn't slipping under hard acceleration, definitely do not
consider replacing the clutch. You would be replacing your good clutch parts
that are capable of producing a one million cycle service life with cheap
china crap that might only last for 60,000 to 80,000 cycles with lower
clamping uniformity performance.
The clutch hydraulic system is extremely important to maintain at peak
performance. If your corvette has the original clutch hydraulic cylinders,
send them to Jim Jandik of Power Torque Systems http://www.powertorquesystems.com/Contact.htm for rebuilding as opposed to
replacing with cast iron aftermarket cylinders when it comes time to service
the clutch hydraulic system. You'll get better results for around the same
cost.
Next, while in neutral with engine running, if you do not hear a significant
increase in free spinning transmission (whirring) noise between when the
clutch pedal is fully depressed and fully let up then you know the pilot
bushing is still in good condition and there is no reason to pull the
transmission. If there is considerable change in noise level with pedal all
the way up, this would indicate need to replace the pilot bushing warranting
necessity to remove the transmission.
Nice thing about C4 manual transmissions is that the transmission does not
need to be removed in order to replace the clutch hydraulic slave cylinder.
Hope this helps.
Best regards,
Bill Boudreau
ZR51 Performance
5612 East Almeda Court
Cave Creek, AZ 85331-6405
United States
602-319-6575
-----Original Message-----
Hi,
First thank you for taking the time to post all this information on the ZF
S6-40 transmission. It is outstanding the detail provided. I have a 1989
that I recently purchased with 56k miles that has sat dormant for 20+ years,
and one of my to do is change out the transmission fluid and clutch
assembly. The reason for sitting was due to a head gasket failure.
Questions
1. Should I wait and get car up to temperate prior to changing fluid, or
change immediately prior to first start?
2. Local dealership provided a fluid different to the two recommended fluids
for this application, 10-4006 aka 88900333. Should I use this fluid, or
return fluid, and seek the two fluid types referenced on your site.
Thanks again and Happy New Year,
Jim
12-30-2015, 03:25 PM
Also have a new gas fill boot on the way too due to mine cracking upon removal.
With the engine in I can roll it into the garage for the remainder of the work and have heat.
Going to have to search hardware store for correct studs. 
