Camshaft break in session.

DEVONMAN · Post by **DEVONMAN** » Tue Feb 21, 2017 11:33 pm

This really is a word of caution regarding camshaft bedding in.
The point of concern is the gearbox.
During the camshaft bedding in session the gearbox will usually be in neutral and this means that the input shaft will be spinning at 2000 ish RPM for 20 minutes and the output shaft will be static. Now if the gearbox has been sitting for some time without oil splash the various needle bearing clusters can suffer due to insufficient oil. My bad experience of this problem is related to a T5 Cosworth gearbox where the interface between the input and output shafts got mangled.

However, it has been know for a needle cluster to seize during the cam bedding session and then the car will creep or shoot forwards.

If you have rebuilt the gearbox I suggest you use the proper assembly grease in the needle clusters. If the box has been sitting around for ages tip the box up end to end to drown the various parts in oil.

In some cases you won't realise any damage was done till the box has a short life.

Letting the box spin in 4th gear with wheels removed may resolve the problem or removing the prop if it's a flange output.

stevieturbo · Post by **stevieturbo** » Tue Feb 21, 2017 11:51 pm

DEVONMAN wrote:This really is a word of caution regarding camshaft bedding in.
The point of concern is the gearbox.
During the camshaft bedding in session the gearbox will usually be in neutral and this means that the input shaft will be spinning at 2000 ish RPM for 20 minutes and the output shaft will be static. Now if the gearbox has been sitting for some time without oil splash the various needle bearing clusters can suffer due to insufficient oil. My bad experience of this problem is related to a T5 Cosworth gearbox where the interface between the input and output shafts got mangled.

However, it has been know for a needle cluster to seize during the cam bedding session and then the car will creep or shoot forwards.

If you have rebuilt the gearbox I suggest you use the proper assembly grease in the needle clusters. If the box has been sitting around for ages tip the box up end to end to drown the various parts in oil.

In some cases you won't realise any damage was done till the box has a short life.

Letting the box spin in 4th gear with wheels removed may resolve the problem or removing the prop if it's a flange output.

Unless the rear wheels are turning...ie the propshaft, then the output shaft will always be static regardless of anything else.

If the clutch is engaged and engine turning...then all internal gears etc will be turning and oil will get around the box very well.
Whether the actual output/mainshaft turns shouldnt matter as all other parts are rotating and oil will be moving.

DEVONMAN · Post by **DEVONMAN** » Wed Feb 22, 2017 12:16 am

It's the 2000 rpm in neutral that does the damage. I was surprised also by this but it happened. If you search this you will find others that have suffered.

stevieturbo · Post by **stevieturbo** » Wed Feb 22, 2017 12:21 am

DEVONMAN wrote:It's the 2000 rpm in neutral that does the damage. I was surprised also by this but it happened. If you search this you will find others that have suffered.

Again, there is plenty in the box that is moving, so there should be no oil supply issues.

Unless there is an output shaft driven oil pump that is needed to supply oil somewhere strange.

Or maybe use 1900rpm ? lol

DaveEFI · Post by **DaveEFI** » Wed Feb 22, 2017 10:06 am

I'm unclear too. The only time the bearing between input and output shaft isn't turning is in a direct top gear. And many boxes have an indirect top gear, so must spend a lot of time with it turning.

There were reports of ZF 4HP autos failing when revving in neutral for emission testing.

DEVONMAN · Post by **DEVONMAN** » Wed Feb 22, 2017 10:36 am

DaveEFI wrote:I'm unclear too. The only time the bearing between input and output shaft isn't turning is in a direct top gear. And many boxes have an indirect top gear, so must spend a lot of time with it turning.

There were reports of ZF 4HP autos failing when revving in neutral for emission testing.

I my case I believe it was the fact that the gearbox was on the shelf for many years and whilst it was good before, it was damaged after the cam breaking in session. I can only think that the parts above the static oil level suffered at the initial start up which went straight to high revs. The T5 gearbox has a cluster of 15 needles in a pocket at the interface of the input and output shaft. The oil supply to these needles is via a small slot which in my opinion is lacking in as much that when the input shaft is spinning , centrifugal force is throwing the oil away from the slot. The ATF oil specified for these gearboxes is thin and probably drained out over time. A thicker transmission oil may have saved the day.

I put this post up to maybe help others avoid the situation I found myself in.

Devonrod · Post by **Devonrod** » Thu Feb 23, 2017 10:30 am

Since this happened to my T5 gearbox, I have found other cases of this, one case the gearbox locked up and the car crashed in to another in the garage, Rod & Custom magazine November 1995 Pat Ganahl one of the editors had built a clean 52 Chevrolet as a everyday runabout, he had the gearbox and souped up engine rebuilt and was breaking in the cam- from the article quote- "how did it do it ? with the car in neutral the cluster wasn't turning to splash oil up onto the main shaft, and with the engine running that fast, second gear seized, effectively putting the car in high gear. Who`da thought it ? but be forewarned " he had to get the gearbox rebuilt again and bent the brand new NOS 52 Chevy grill and new front wing ! if you look at gearbox build up videos you will see them coating all the parts with special grease, the gearbox rebuilder in this case didn't do his job right, here is a picture of the gearbox in my case, the damage is the needle roller surface where the input shaft fits, I suppose one way round it is to wedge the clutch pedal down while you are breaking the cam in ?

stevieturbo · Post by **stevieturbo** » Thu Feb 23, 2017 11:09 am

With the car in neutral the cluster is always turning. ( engine running, clutch engaged of course )

Oil is splashing and moving everywhere.

DaveEFI · Post by **DaveEFI** » Thu Feb 23, 2017 1:54 pm

stevieturbo wrote:With the car in neutral the cluster is always turning. ( engine running, clutch engaged of course )

Oil is splashing and moving everywhere.

And if it 'selected' second gear, it means the second gear pinion seized on the output shaft. It normally turns on that until locked to it by the synchro unit when the gear is engaged.

My guess is there was no oil in the box.

stevieturbo · Post by **stevieturbo** » Thu Feb 23, 2017 2:21 pm

DaveEFI wrote:
stevieturbo wrote:With the car in neutral the cluster is always turning. ( engine running, clutch engaged of course )

Oil is splashing and moving everywhere.
And if it 'selected' second gear, it means the second gear pinion seized on the output shaft. It normally turns on that until locked to it by the synchro unit when the gear is engaged.

My guess is there was no oil in the box.

But it wont be selecting any gears unless they've been trying to, and sitting with their foot on the clutch

Clearly they've had a problem, but their reasoning does not add up based on the info given

Devonrod · Post by **Devonrod** » Thu Feb 23, 2017 3:57 pm

I could not comment as I am not familiar with the inner workings of a 1952 Chevrolet gearbox, but any one can see that if a gearbox component is in contact of another without any lubrication for 20 minutes at 2000 revs there is bound to be trouble, another word for it is friction welding lol..........

DaveEFI · Post by **DaveEFI** » Thu Feb 23, 2017 4:08 pm

Synchro boxes are all of a pretty similar basic design. The gear pinions are in constant mesh with the layshaft so idle round on the output shaft until locked to it by the synchro mechanism. So just why one would seize to the output shaft with the box in neutral but not when running, I can't guess.

ChrisJC · Post by **ChrisJC** » Thu Feb 23, 2017 6:09 pm

A very interesting observation.
I know the early ZF4HP22's had a 'bug' which the Californian smog test exposed. If the gearbox has been run, when you select neutral there is a bit of drag. The smog test required the engine to be run at 3000RPM for a period, which caused the gearbox to overheat and fail. They fixed this in later ones.

I don't think the R380 is affected as the oil pump seems to be driven by the layshaft which always turns. Can anyone confirm this point?

Thanks,

Chris.

stevieturbo · Post by **stevieturbo** » Thu Feb 23, 2017 7:36 pm

Devonrod wrote:I could not comment as I am not familiar with the inner workings of a 1952 Chevrolet gearbox, but any one can see that if a gearbox component is in contact of another without any lubrication for 20 minutes at 2000 revs there is bound to be trouble, another word for it is friction welding lol..........

But again....how could it possibly not get lubricated when there is so much oil getting thrashed around by all the rotating gears within the box ?

Devonrod · Post by **Devonrod** » Sat Feb 25, 2017 4:02 pm

But again....how could it possibly not get lubricated when there is so much oil getting thrashed around by all the rotating gears within the box ?[/quote]

Did you see the above photo ? there was nothing wrong with the gearbox before it was installed apart from lying under a bench for several years, the new ATF was put in after the engine and box were in place, the photo speaks for itself. there was an immediate whine that was never there before when the car was driven.

The V8 Owners Forum -

Camshaft break in session.

Camshaft break in session.

Re: Camshaft break in session.