Does anyone know what the pinion angle should be for the SIII IRS? Also, can anyone confirm at what angle the engine\gearbox sits when properly installed? Is it dead level or does it slope down toward the tail end of the gearbox?
Background:
I have a JT5 installed as a conversion from automatic and get some vibration at high speeds(over 65). Tires are balanced, all U-joints are new on the balanced driveshaft and the axles. I noticed in the parts manual that the gearbox spacers for the rear trans mount are different between auto and manual(c32458/2 vs c7493). Anyone know the difference in thickness? Seeing as how I converted from auto to manual and only had my original spacers, could the difference in thickness of those spacers cause enough of a change in the driveline angle between the engine\gearbox and the differential pinion angle to be the source of the vibration? The trans mount on the JT5 is totally different that the original, no spring. The mount is similar to a chevy trans mount, being made of rubber, similar to the engine mounts except rectangular, not round. Also, the manual indicates spacers for the motor mounts showing “as required”. “Required” to achieve exactly what? Engine height? Engine tilt side to side? Which one?
I know the two angles are supposed to be in parallel(e.g. engine 3* down - pinion 3* up) and that too much of a mismatch can cause a driveline vibration.
I have not been able to find this documented anywhere. If it is, could someone please point me to it?
I plan on doing some measurements in the future but would like to know what the angles SHOULD be as a starting point so that I can set everything right.
I am an amateur mechanical engineer and think the driveshaft angle should not be a factor unless the face of the differential input flange is not parallel to the face of the transmission output flange which is very unlikely
Firstly I would suggest to ensure that the driveshaft was assembled so the joints are in-line as below
Secondly, rather than ask for angle measurements, I would suggest just simply measurements from certain points
Apparently it’s NOT close enough right now. I am just not sure at this point which way it needs to go. I was thinking that once it is set up correctly I could go from there if the problem still exists.
If you have a smart phone, most of them include an angle measurement feature.
Measure the angle on the input flange of the IRS, and the output flange of the transmission, are they within the specifications of the design article I referenced? Ideally they are parallel to each other. They can be offset in any direction, but They need to be roughly parallel. If they’re not parallel, start shimming.
That’s the plan, just need one of those new fangled Round TUITs. Still, I’d like to know what all the variables are supposed to be as designed. Considering that this involves 2 motor mounts, possibly with spacers, the IRS cage mounting, and the trans mount shimming(the REAL unknown - JT5), getting just one set right and having the others NOT right could lead to problems I haven’t even thought of.
I’m sorry if I’m repeating myself, and others may chime in here….but I think you’re over thinking this. The IRS is really not changeable, the only adjustment you have would be a very slight angle change on the engine. Any transmission will have parallelism between input and the output. I think you won’t have a problem.
I am with WWayman - don’t over think this. Alignment in an an E-Type is not an issue - my Land Rover has angles of up to 20 degrees and I have no issues. If you have vibration, then if shaft related, it will be balance, bent shaft, phasing or faulty UJs but not alignment in the E-Type.
If none of the above then look elsewhere such as the conversion alignment - gearbox with engine - it has been known for the bell housing alignment to be out - lots of other things to look for.
That was my first thought, but it’s present with 2 different sets of tires on different wheels. The second set is new, so I really don’t think it’s wheels\tires.
It’s a Jaguar bellhousing adapted for the JT5 by Classic Jaguar. I haven’t seen any issues with it’s alignment. After setting up the clutch with an alignment tool the trans slides right in, no muss, no fuss. Perfect fit.
In my original post I really should have defined better the high speed aspect of the vibration, it’s actually around 80 and over. The driveshaft has been checked twice for balance so that’s why I’m thinking more about the angles, especially the engine\trans. Jaguar must have had a reason for specing different gearbox spacers for the auto and manual. There is a difference in thickness, I just don’t know how much. I suppose all will be revealed when I finally get around to actually taking measurements.
What do you mean by “different gearbox spacers”? Are you referring to distance between the two faces of the Bell Housing, as there are no individual spacers in addition to the Bell Housing?
The difference in the length of the Bell Housings for Manual and Auto transmissions is simply to accommodate the different transmissions and what protrudes forward of the front face of the specific transmission.
The fact that the transmission slides on OK when the clutch plate has been aligned means little. I’ve seen After Market bell housings made specifically for the adaption of alternate transmissions to Jaguar, where the faces of the Bell Housing have not been machined parallel and they would slide on fine, right up to the rear face of the engine and accept the securing bolts, only to be ultimately pulled out of alignment when the face that interfaces with the engine was pulled up tight with the bolts.
If you look in the SIII parts manual at the transmission mount you will see parts numbered c32458/2 and c7493, one for auto and one for manual. These spacers fit between the trans mount plate and the floor, one for each of the five bolts that attach the mount plate to the floor. The thickness of these spacers will determine the height of the transmission tail shaft and thus the driveline angle. Spacers under the motor mounts will also have an effect on the driveline angle. The motor mount spacers are listed as A\R (As Required). I don’t know what the requirement is for these, but the combination of the gearbox spacers and the motor mount spacers will determine the driveline angle.
My bell housing is an original from Jaguar(not aftermarket) and has not had it’s surfaces machined which would alter it’s original dimensions. I don’t think the parallelism of the bell housing is the problem here. Just the overall driveline angle.
I hope that makes clear what my concerns are. Thanks for your insight.
The difference in length between the Manual and Auto transmission assembly from the interface surface of the engine for the Bell Housing, to the face of the transmission Companion Flange face is less than 6mm (less than 1/4"). Over the distance from the front engine mounts to the transmission support, the angularity difference would be infinitesimal. The difference in the transmission mount plate and spacers is for the different configuration in that area of the two types of transmission, not to vary the height of the transmission centre line. .
Similarly, the packers for the front engine mounts are to take up the variability of the engine mounts and to ensure even and adequate clearance between the top of the engine frames and the carburetor/manifold assembly. .
You’re overthinking the Drive Line angularity by a mile and I very much doubt that its got anything to do with your issue.
Steve…is your diff original to your car and its mount brackets…the diff mount brackets are specific to E types…useing brackets from other model Jags will set the diff at a different angle…Steve
Hi Steve…are you on wire wheels. …if so and you mention that your wheels are balanced then i would question how they were balanced…standard tire shops just use standard type balance cones…wire wheels need special cones to balencing them…most shops dont have them…the cones replicate the spinners…Steve
Hi Brent,
I wholeheartedly agree, but this was never my concern.
Makes a lot of sense and I had figured that was the reason, however, never having had the Jaguar manual transmission to compare to my old auto, I have no way of knowing what the distance difference is. Seeing as how the JT5 kit was most likely to have been intended as a replacement for the factory 4 speed, not an auto conversion, there was never any attempt to address the spacer differences.
You could be right on this, though I have never found any documentation to support this or explain the A\R (As Required) notation in the parts manual. No mention is made of these spacers in the service manual either.
Adding spacers to the engine mounts raising up the front of the engine will definitely have an effect on the driveline angle. Especially when you consider those spacers are 3 mm each.
Thank you for your insight, it’s certainly given me food for thought.
No, my first set were the factory chrome disc wheels and my current set are custom made Budnik alloy wheels. What’s frustrating is that before the rolling chassis was rebuilt I never had any high speed vibrations at all.
Future plans call for running it on jack stands with the wheels removed in an effort to isolate the problem. Should be interesting. 90 mph on jack stands!
