Taking the 96 vdp in next week to get the engine and transmission oil changed. What else should I have the mechanic check when he is underneath the car? I remember someone mentioning possible loose bolts in the steering rack. Any other hardware that forum members have found to be loose?

I will have him check out the front end also. I think I remember reading about possible loose bolts in the driveshaft also. Ground strap is another thing I will have him check.

I will make up a list of things for him to check with your help.

 

Hi Scotlad,

Just a few thoughts:

Don't just have him check the engine ground strap, have him disconnect it, clean both ends with a brass brush and zero-residue electronic cleaner, allow to dry and reconnect.

All suspension bushings are suspects, including the two large ones on the rear subframe outer corners where they mount to the body.

Check the wheel bearings, especially the fronts which may need to be repacked and adjusted.

Check the differential output shafts and pinion for signs of oil leakage (usually indicating worn bearings).

Check for rust on the subframes or any other critical safety components.

Check for fluid leaks.

Choice of transmission fluid is important in the ZF 4HP24. The original specification was Dexron III, with a viscosity index of 190, but it is no longer available, and modern Dexron VI is significantly thinner, with a V.I. of something like 146. The best fluid I know of for this gearbox is Redline Oil D4 ATF, with a V.I. of 188, and a good second choice is Mobil 1 ATF, with a V.I. of 176-199 depending on what MSDS you consult. These numbers are off the top of my head but I think they're close. Going from Dexron VI to Redline Oil D4 ATF in our '93 with the same transmission as your car completely transformed the performance and I realized that with Dexron VI the torque converter must have never been fully locking up.

Cheers,

Don

 

Thanks Don ,

As I considered the thinner D6 without knowing the V.I. but knowing it was thinner then the D4 delivering better torque converter efficiency and the possible shifting lag at low atmospheric conditions . The Redline may be more expensive but the return on investment time in better fuel economy should be short . I want it to chirp in 3rd if the X300 N/A normally does .

There was mention from someone about 2 grease zerks that I believe where on the driveshaft universal .

Look for a gap on the top of the front shocks as it compresses the tower bolt bushing over time , and look for sunshine though the front shock lower bushing , Bob said the cheap lower bushings wear out fast .

Under the car is about the only way I know of to address the large woven engine ground strap what should be a scheduled maintenance item for the trouble it can cause .

 

Hi Parker,

I'm not sure I follow. Since the ZF 4HP24 was designed for Dexron II/III, with a viscosity index of around 190, why would Redline Oil D6, with a V.I. of 163, be preferable to D4 with a V.I. of 188? Torque converters (and the rest of the gearbox) are designed around specific fluid viscosities and friction/slippage characteristics.

While running Dexron VI in our '93, I assumed that because the transmission shifted smoothly that all was well. But when I changed to Redline Oil D4, suddenly I had engine braking again when descending hills, and in Sport Mode the transmission held the lower gear longer when exiting turns. I had forgotten how the gearbox was supposed to behave. Something was definitely not working properly on Dexron VI, and for similar reasons I would not expect D6 to work optimally.

Can you expand on your thoughts about torque converter efficiency?

Cheers,

Don

 

The grease fittings Parker mentioned - 4 total on the car, 2 on each rear halfshaft, one inboard at the universal next to the diff, the other outboard on the universal at the hub.

Check condenser mounting bushings. Particularly the lowers. May as well check the radiator bushes, as well.

Fuel filler compartment - I'd have him give it a blast of shop-air. Various flora and fauna lodge in there if you park outside much, and clog the drain port. Excellent way to introduce water to the fuel.

Check for signs of oil leakage at the horseshoe oil cooler bypass at the oil filter. If leaking, 4 o-rings will set you right.

 

aholbro1, I have changed out the condenser and radiator bushings already and I do have him grease the halfshafts. I guess what I was asking was, what nuts and bolts and other hardware loosens up with wear and tear. I think I remember someone saying that the shifter bracket hardware on the side of the transmission can loosen up. The front wheel bearings have been greased and adjusted. I do keep an eye on the fuel filler compartment filter, it was plugged when I got the car.

Don B, you have me thinking about buying different trans. fluid. I had already bought 2, 4 quart jugs of Valvoline full syn. transmission oil in the red container. It was cheap, around $18.00 per jug. The V.I. for this oil is 156. As you said the V.I. for Redline D4 is 188, it also has a higher viscosity @ 100 degrees 7.5 compared to 5.91 with the Valvoline. I did notice at lower temp 40 degrees the D4 has a viscosity of 35.4 as compared to 28.82 with the Valvoline, better flow at low temp?

I will go to Oreilly's today and check out what they have. I take the vehicle in next Thursday so I do have some time.

 

It's easy to think in terms of "better flow at low temp," but you have to remember that the transmission was designed around the properties of a specific fluid, Dexron II/III. If ZF, the manufacturer of the transmission, thought that better flow at lower temperatures was worthwhile, you would think that today they would recommend we fill our gearboxes with one of their newer, lower-viscosity fluids like LifeGuard 5, 6 or 8. But they don't. For the 4HP24 they still recommend fluids conforming to the original specifications of Dexron II or III. See for yourself on page 4 of the current list of lubricants from ZF's website:

ZF Passenger Car Transmission List of Lubricants 01.04.2018

Regarding Valvoline, I use a lot of their fluids, but I take issue with their claims about some of their transmission fluids. They claim, for example, that their MaxLife Multi-Vehicle Transmission Fluid meets the specifications for, among many others, Dexron II/III, Ford Mercon SP/ZF LifeGuard 6, and ZF LifeGuard 8. Yet, ZF specifies different fluids for their various gearboxes: Dexron II/III for the 4-speeds, LifeGuard 5 for the 5-speeds, LifeGuard 6 for the 6-speeds, and LifeGuard 8 for the 8-speeds. You would think that if LifeGuard 8 was a superior "new" fluid, ZF would recommend that all their transmissions be retrofitted or "upgraded" to LG 8. But they don't. Another example is that Valvoline claims their fluid can be used in transmissions for which Mercon SP or Mercon LV was originally specified, yet Ford expressly states that Mercon SP must not be used in vehicles for which Mercon V or LV was originally specified:

https://www.fcsdchemicalsandlubrican...ission%20Fluid

So what does Valvoline know that ZF and Ford do not? I think they know how to compromise on performance in order to make one fluid "work" in multiple transmissions and to therefore profit by economies of scale. Given that ZF and Ford don't believe one fluid can perform optimally in transmissions designed around very different fluids, I don't trust Valvoline's claims.

P.S. If you can't find Redline Oil D4 ATF, you can probably find Mobil 1 ATF, which is approved by General Motors as a Dexron III replacement and is being successfully used in the 4HP24 by some of our members.

Cheers,

Don

 

Don, I am confused by your statement that Dexron III spec transmission fluid is no longer available.
I attach Castrol Transmax Dex/Merc product data sheet & believe that it plus many other Dexron III fluids are available in the USA.
Here in Australia we have a wide range available, but one has to note they are for Dexron III ( and II ) but do not extend to Dexron V1 as pointed out on the sheet.
I use Castrol Transmax Z (fully synthetic) in my XJR (4L80E auto) which specifically points out also that it is a Dexron III type auto transmission fluid intended to satisfy both Dexron III & II, it does not meet the later Dexron specs which are not suited to my transmission.

John Herbert

 

Hi John,

I believe I stated that "Dexron III" is no longer available, not "Dexron III spec." Dexron is a registered trademark and brand of General Motors, who licensed the Dexron III name to third-party fluid makers. All of those licenses expired permanently in 2006 and since that time no fluid branded Dexron III has been available.

A number of fluids available today claim to meet the Dexron II and/or III specs, but if you review their Material Safety Data Sheets you will find that many of them have viscosities lower than pre-2006 Dexron III. So my point is, do your homework. Don't simply trust the claims of the fluid maker or marketer. Viscosity isn't the only specification that matters, but it's a critical one, and my experience is that our 4HP24 did not perform optimally on lower-viscosity Dexron VI.

Cheers,

Don