I bought new front and rear transmission ball bearings for my '68 Series 1.5 (NSK and KOR). The outer and inner bearing diameters matched the original Hoffman bearings exactly but the retainer ring groove locations/thickness were a little different. The end result was the input (constant pinion) shaft ended up 0.020 inches forward of its original location in the transmission case and the main shaft 0.033 inches aft. My guess was the shift clevises could deal with the main shaft being 0.033 inches aft but the net 0.053 inch increase between the input shaft synchro cone and 4th gear synchro ring was too much. The gap between the two shafts was evident with the new bearings in place. The original Hoffman bearings were in serviceable condition so I ended up using those in the final assembly. Has anyone had problems/success using new bearings?
I have a 67 S1 and just starting restoration of the vehicle. 4.2 gearbox is first. Dissembled and new parts arrived. Read this post and checked my New vs. original rear bearing. Same issue. Have not checked new front bearing yet. I hope I can use my New set but will see and update this post. I bought KSM front and KOR rear.
Also noticed each new bearing has 8 ball bearings each while the originals have only 7 ball bearings each. Hmmm…
The pro who rebuilt my gearbox prefers to order the bearings without a circlip groove and then have the grooves machined by a specialist. My car has a Moss box and the Hoffman bearings were so machined, maintaining factory tolerances. FWIW. Paul.
@angelw ? Any insights?
The KSM Bearing can be purchased with and without the Snap Ring. All KSM bearing suitable for these gearboxes have had the Snap Ring Groove in the correct position. However, I purchase them without the Snap Ring Groove, as I prefer to machine them myself and, as I’ve told Paul Wigton many times, “I’m so poor, that when at school, I couldn’t even pay attention”. The KSM Bearings without the Snap Ring Groove are cheaper. I don’t like the KOR bearings much.
The position of the Snap Ring is one thing and it needs to be correct, but another issue is the size of the radius between the face of the inner race and its bore, of the rear bearing. The original Hoffman bearing had practically no radius whatsoever and the reason for this is that the Oil Pump Drive Collar is driven only by frictional contact with this face. Following is a picture of the face in question of an original Hoffman Bearing. Note that the witness mark left by the Oil Pump Drive Collar is rather narrow. Its actually circa 5mm.
The next picture is of the same style of bearing being sold by the regulars. Note that the radius between the face of the inner race and its bore is quite large in comparison to the original. Most bearings for replacement of the Hoffman Bearing has a radius of circa 4mm to 5mm, leaving not much of a margin for the Oil Pump Drive Collar to interface with.
This small contact area leads to deformation of the face of the Oil Pump Drive Collar and once this starts, the failure is exponential.
When I machine a component that is to be heat treated and finish machined, I machine the part with the Finishing Allowance shown in the following picture. In each of the following pictures, the Green Lines represent the finished surfaces after Finish Machining.
In this way, when the part is Finish Machined, the finished surfaces will be tangent to any radius feature that may be included. Many don’t take the trouble and I believe KSM Bearing are an example of such, for the finished face and bore of the inner race are not tangent to the radius between the two surfaces, as shown in the following picture.
This is a happy coincidence, because it increases the bearing area between the face of the inner bearing race and the face of the Oil Pump Drive Collar, to an acceptable level.
Pardon me for being a little bit dense–it is only 5:45 in the morning here–but I don’t understand how it is you fix the radius on the bearings to cure the oil pump problem. Do you actually re-machine the inner race of the bearing?
I’m giving an example why the KSM bearings are an acceptable replacement. If KSM were to rough their bearing blanks out as I rough parts out that have to have a finishing operation post heat treatment, so that all surfaces after finishing are tangent with any deburring rads, or rads to circumvent stress points, then they would suffer the same issue as many of the bearings sold by the regulars; too small a bearing surface for the Oil Pump Drive Collar.
It just so happens that KSM must rough their blanks so that the face and bore of the inner race are tangent with the corner radius prior to heat treatment and finishing. Accordingly, when the finishing allowance is machined down to the finished surface, you end up with corner detail as shown in the last picture of my previous Post. This just happens to be a happy coincidence for this bearing to be used in the E Type Gearbox. If you compare the two last drawings in my previous Post, its clear that the bearing area made available is shown to be greater in the last picture, than that of the second last picture.
However, I have modified the bore/face corner area of some bearings by machining a recess in the face of the inner race and expansion fitted a hardened and ground spacer (washer) to get rid of the corner radius.
One of my questions above did not get addressed. Does it matter that the original bearings had 7 bearings and the replacements have 8 bearings. Would like to attach a picture of my original and replacement set but cannot find a way to do it on this forum. Maybe not enough permissions as I’m a brand new member.
KSM front bearing circlip distance from front face and rear face looks like an exact match.
KOR rear bearing circlip distance from front and rear face does not match. I may need to return the KOR rear bearing and find a KSM rear bearing.
If you look at the bearing pictures in my previous Post, you will see that one is of an original Hoffman Bearing, with practically no radius between the Face and Bore of the inner race, and an unacceptable replacement being offered by the regulars. You will note that the original has 7 ball bearings and the replacement 8; accordingly, you won’t have to attach pictures yourself.
Both bearing are deep groove type and are primarily radial load bearing, that can accommodate some moderate end thrust. There will be no issues whatsoever using a bearing with eight ball bearings.
The KSM bearing you need is an RMS11-NR for the rear bearing replacement. This bearing has 8 ball bearings.
Thanks for sharing your experience Bill - the E type transmission rebuild has some details that can really bite if not aware of them.
Hello again. The Oil Pump Drive Collar is driven only by frictional contact with the face of the inner ring of the bearing.
I have not been able to locate a vendor with the KSM RMS11 bearing.
I’m curious as to what the possibility is that a machine shop could make an oil pump drive collar with an increase the surface area such that it replaces the surface area lost due to increased bearing radius?
I checked and it seems like there is clearance in the rear end cover to allow for an increase in the collar size.
@angelw will have your answer: search under his nick and the topic.
I saw Bill mentioned “However, I have modified the bore/face corner area of some bearings by machining a recess in the face of the inner race and expansion fitted a hardened and ground spacer (washer) to get rid of the corner radius.”
I do not have the tools and ability to change an off the shelf bearing with an expansion washer.
I’m thinking I can have a shop make an oil pump drive collar with an increased OD at the end of the collar that comes in contact with the bearing face.
Perhaps Bill could make you one?
Thanks guys. I will check the two links and if not there I will PM Bill to see if he would be willing to make a modified oil pump collar.
I can supply you with RMS 11 bearings if you luck out locally. I’ll also look at making a custom Oil Pump Drive Collar to see if there are any complications.
Bill, I’m thinking about rebuilding a spare EJ gearbox and would be interested in a “positive drive oil pump kit” if that is feasible. Thanks.
To answer your original question …
Yes. I rebuilt my gearbox twice. The first time I used replacement front and rear bearings - can’t recall their manufacture - from one of the regulars and was unhappy with the result. Just a little sloppy. I took them out and replaced them with a good, used pair supplied by @Robert_Laughton and they cured the problem. You really need to make sure to install 100% compatible replacements.
Do you mean by arranging some manner of drive direct from the Main Shaft? That would be possible for sure. However, one of the main problems with most of the replacement bearings for the rear, is that the margin of contact between the Oil Pump Drive Sleeve (OPDS) and the face of the rear bearing’s inner race is so small (see the pictures below of an original bearing and typical replacement) that the pressure exerted for a given torque of the Companion Flange nut, that the corner between the front face and bore of the OPDS may and does deform, leaving the nut and the whole system not as tight as it started.
When the OPDS is driven by friction alone, this loosening of the clamping force is significant and further failure is exponential. I believe the deformation of the PODS would still occur with it staked or by some means driven directly. The Speedo Drive gear is also driven by friction. Accordingly, its drive is also affected by any diminished clamping force applied by the Companion Flamge nut.