Getrag transmission problem on low mileage Fiero GT (Page 16/17)
hobbywrench SEP 05, 04:20 PM
Moar, Great pictures and I must say if you could convert your personal energy applied to your project into the car somehow you would not need an engine. Great work. I guess we Americans can take heart that "big brother" has not dropped on us as hard as in Austria.

I can not tell much from the pictures, but so many chips does not seem normal. The fact that your trans oil level has dropped while leaking suggests something could have been starved of lubricant and cooling for a period. And you did not tell us how hard the test run was while this was happening. I know you put in a lot of research on the preload of the diff bearings. Were they tight after you used your gauge(s). The stub end engagement of the inner spline is something to consider , but I cannot picture how it would play. During slight movement could that stub end gouge the female spline?

Edit: That is good work on the springs. I know how difficult refoming and flattening is. I am glad to see you are not afraid of heat on the end of the spring . Do you gain camber adjustment with both the flat sided bolts AND the slotted spring seats?

[This message has been edited by hobbywrench (edited 09-05-2016).]

Moar SEP 08, 02:07 PM
I´m 100% sure that there was always sufficient transmission oil in my tranny during test drives.
I have recognized early that the new axle shaft seals are leaking. One side already started leaking after driving the first few meter (just a little bit, but it became worse and worse over time).
For this reason I always kept attention to the oil level. The leakage of the left axle shaft seal became extremely worse during tire/wheel change AFTER my last test drive.

Furthermore, I always drove with ½ power during test drives (only up to 3500 rpm, not more).
I cannot imagine that there has something overheated. Usually oil changes its color after a few overheating cycles (becomes darker and darker).
But the color of the trans oil has not changed.
Besides the metal particles the oil looks like new.

Regarding the preload I am sure the diff bearings are tight enough (and there is absolutely no play).
They are even slightly tighter than recommended.
(I have used a shim 3 sizes larger than ZERO lash, whereas 2 sizes larger is recommended in the Getrag manual).
The reason for this decision was that the bearing cones and races came from different manufacturers. (brand new KOYO races mixed with slightly used TIMKEN cones)
I thought a little bit of extra preload will help to compensate the additional preload-lose during run-in caused be the mixing of different bearing manufacturers.
Hope that this was not a bad decision...

Suspension work:
My intention was to get a lowered and nice handling car whereby keeping an “original” suspension look for low $$$.
I know I should have pained the springs black here in Austria.
However, I hope that I will pass the next inspection also with red springs.
The maximum possible neg. camber is -2.8° (with slotted strut mount plates & camber bolts).
In my first Fiero I only installed camber bolts and I think more than -1.8° was not possible.

[This message has been edited by Moar (edited 09-08-2016).]

Patrick SEP 08, 02:17 PM

quote
Originally posted by Moar:

The reason for this decision was that the bearing cones and races came from different manufacturers. (brand new KOYO races mixed with slightly used TIMKEN cones)



Using new bearings with old cones is never a good idea.
Moar SEP 08, 02:46 PM
Yeah, I know.
If I wouldn´t live in Austria and if I could buy a set of new high-quality TIMKEN bearings in the next hardware store then I wouldn´t have done this.
I prefer TIMKEN bearings over Austrian SKF bearings. Expensive doesn´t always mean great quality...

But maybe a new set of SKF cones & races would have worked better compared to my KOYO/TIMKEN mix.
However, I have compared bearing main dimensions and angles before combing them (no differnce).
I cannot say anything about bearing micro geometry, since I don’t have the right tools for this.

Moar FEB 17, 01:16 PM
In the meantime I have gotten replacement seals and a lot of other Fiero spare and performance parts.

Thanks to Nelson!

I will show you how good Toyota RAV4 axle shaft seals fit Fieros


1. Step: Removing suspension components and drive shafts:

I have found out that a belt much easier to push out the drive shaft:



2. Step: Removing old axle shaft seals:

Here you can see how I remove parts of the damaged seal - worn seal metal cage:

As you can see on above picture the seal was loaded with high axial forces!


Seal completely removed:



Failure analysis:

Light wear on the bronze axle support bearing:

I think that the gold colored metal particles in the transmission oil are coming from this weak bronze support bearing (drivers side in my case).
Maybe this wear is normal for this type of support bearing (bearing break-in).

Unequal axial wear on axle shaft seals:


Unequal axial wear means that the tranny is not centered accurate enough.
However, centering the tranny will just diminish but not eliminate the problem.

You may wonder why I am facing these axle shaft seal leakage problems while others don´t.
Well, I think the main reason for my problems are support bearings and the LSD.
Axle support bearings have a considerable protrusion compared to OEM axle shaft seals (about 10 mm).
Furthermore, for the LSD upgrade it was necessary to cut the ends of the drive shaft splines.
Obviously, I cut my drive shafts 2 or 3 mm too shot, which means that there is no “axial stop-surface” inside the differential anymore.
These two main reasons in conjunction with high negative camber of -2.0° lead to axial preload on axle shaft seals!


Ideas - problem solving:
- Centering tranny in cradle
- Axial stoppers inside diff
- Alternative axle shaft seals with elastic lip (TOYOATA RAV4 seals)
- Shorten drive shafts
- Reducing negative camber


Implementation of ideas:

Fist I measured the required thickness of the “axial stoppers”.
I used a bubble gum and put it onto the drive shaft tip and inserted it into the differential to obtain the required thickness of the “stopper”.
IICRC the required thickness was 3 mm.

I have found out that O-rings fit perfectly into the LSD and that I can use them as “axial stoppers”



Then I have installed new axle shaft seals:

Tip: Use a old brake caliper piston for installing axle shaft seals, if you don´t have special tools (1.6 Miata caliper piston in my case).

New axle shaft seals in place:



BTW, do not forgett to put grease on the seal lips before installing drive shafts!


Next I replaced the OEM engine mount with a polyurethane mount from Energy Suspension.

Comparison of OEM engine mount with poly mount:

The poly mount is much smaller, but stronger!

New poly engine mount in place with a heavy duty spacer plate:


The spacer plate thickness was adjusted to level the engine/tranny perfectly horizontal with
the shorter ´79 Dodge Ram tranny mounts in place (which were installed last year):



Now the engine/tranny is perfectly centered and horizontal!

In order to shorten the drive shaft length a few millimeters, I just loosened the small CV-joint boot clamps (inner ones), pulled the boot ends
approx. 5 – 10 mm inwards and squeezed them to get all the air out and tightened the clamps again (this will reduce axial force a bit).

Furthermore, I have reduced camber form -2.0 to -1.4 deg.


I have also measured transmission drag torques in order to validate differential bearing preload to be sure that nothing is wrong with my bearings:


This is how me measure bearing drag torque in Austria
In Austrian hardware stores I couldn´t find a drag torque measurement tool, therefore I made this “stone age tool”.
Next tool which I will order in USA...

Drag torques:
neutral: 158 N.cm
1st gear: 300 N.cm
2nd gear: 188 N.cm
3rd gear: 192 N.cm
4th gear: 165 N.cm
5th gear: 231 N.cm

[This message has been edited by Moar (edited 02-19-2017).]

Moar JUL 07, 03:03 AM
Update July 2017:

On 2nd Mai my lowered Fiero passed inspection with a ZEX stealth nitrous system in place and since then I drove the car without any problems
Also no axle seal leakage anymore with the new TOYOTA RAV4 seals – I highly recommend them over OEM seals!

I´m drove already 4000 km with the new LSD differential and the transmission keeps working so far!

BTW, the car is very funny to drive with a limited slip diff (40%)!
Very easy to make donuts

Recently, I changed the transmission oil (1st oil flush recommended after approximately 1000 miles, 2nd after 5000 miles).
I have opened the drain plug and have recognized how thin this 75W90 stuff is when hot – thin like water!
The oil was contaminated with many small metal particles – it looked similar to a brown/gold metallic paint!
I think this seems to be normal for the first oil flush (I haven´t found any big metal particles in the oil, only extremely small ones).

However, I upgraded to HYPOID 90 LS (= 85W90) GL5 transmission oil which is approx. 27% thicker compared to 75W90 at operating
temperature and has high-pressure additives as well as special additives for LS-differentials. Compared to the original transmission oil (5W30)
the dynamic viscosity of 90LS is 88% higher at 90°C, which should give sufficient increase of flank safety factors, protection against pittings
and additional protection for bearings.


------------------
Patrick, Analysis Engineer
´88 Fiero GT 5-sp. Getrag

[This message has been edited by Moar (edited 07-07-2017).]

Moar JUL 07, 03:08 AM
Unfortunately, Photobucket has recently turned off free picture hosting.
Can someone recommend a free alternative to Photobucket?

[This message has been edited by Moar (edited 07-07-2017).]

yamahasrx700 JUL 16, 09:54 PM
Thanks for the info
hobbywrench APR 09, 12:06 PM
Just ran across this old thread while reviewing cold start data. Still driving my 85 GT . I am downsizing and hate to think of sending the rebuilt tranny to the scrap yard crusher. If anyone wants it speak up. I did get a torque reading off the input spline shaft...about 1-2 ft libs.
Moar APR 09, 03:33 PM

quote
Originally posted by hobbywrench:

Just ran across this old thread while reviewing cold start data. Still driving my 85 GT . I am downsizing and hate to think of sending the rebuilt tranny to the scrap yard crusher. If anyone wants it speak up. I did get a torque reading off the input spline shaft...about 1-2 ft libs.



Hi hobbywrench, your torque readings (1-2 ft-lib = 136-271 N.cm) are very similar to what I have measured on my own tranny and seems to be OK.
My Fiero 5-sp transmission is working without any problems since the rebuild, I just need to replace the shift selector cable and then everything will be perfect again.
Anyway, I hope that you will find someone who pays a fair price for your perfectly rebuilt transmission.