All about the classy MG Magnette ZA, ZB, Mark III, Mark IV Saloon.
Since I'm pulling the engine for a new rear main seal today (yes a GOOD one), I thought I'd post a couple pics of the tranny mount I use for the Datsun setup. Its just 1/4" plate, and the mount could be a simple 1 3/4" box tube welded to the plate. I had the chunk of original crossmember that I welded in place, although the box tube would be simpler and more effective (another design as you go situation.) I can make tracings of this if anyone wants to copy it?
Jeff,
Yours looks very similar to mine - except yours is cleaner!
I intended to mention that I don't really know the origin of mine - it either came from Novus in California or it was made up for the previous owner. When I first saw yours, Jeff, for a moment I thought it was mine - they look like they were made by the same guy! Except, whoever did make mine had to add 5/16" in shims - which I have saved as you can see. I'll have to figure out a neater way to make that up. I see both utilise the Nissan transmission mount - which I'm told is bullet-proof. Neither is quite like the one Rivergate made for me - on a car I sold a few years ago.
(I'm learning that once you upload the picture(s), these messages upload with them and there goes any chance you have to add to or edit them. While I'm at it, I'll stick in a couple more pix.)
Cheers,
Allen
Its interesting that your mount is centered on the plate, where mine is welded toward the back much further. Note how your plate is square and mine is offset on one side? Is there another set of holes under the car to mount the plate further rearward, or do I have an odd setup? When I built mine, I shimmed the mount on the plate as needed, then welded it all together. That would be fixed by using a piece of 1 3/4" box tube for the mount in my case. What is the distance from the top of your tranny mount to the plate? Mine is about 2 5/8".
You could eliminate those shims by welding a small plate onto the mount, where the single bolt passes through. That would mean less fiddling when you put it in the car.
The 2 steel rods on mine are for rubber (late model Ford) exhaust hangers. Not original, but they work very well!
By haveing a flat plate ,does that mean your exhaust hangs pretty low?
Its no big deal. The exhaust is right below the plate in the center of the car (in my case its dead center), so I haven't had any issues with clearance.
Andrew,
I was afraid the low exhaust might be a problem, but I never bottomed out on it. The exhaust pipe is no lower than it is on a stock MGB.
Jeff,
' Didn't notice yours was offset until you mentioned it. I'll be under my car tomorrow and will check on alternative holes for mounting the cross-member. As to height - it depends on where you measure. On the "front" side of the bolt hole ears (where the mount bolts to the gear-box) it's 2-7/16". On the rear side of the bolt hole ears (the side with the exhaust hanger), it's about 2-3/8". In broad terms, mine is 1/4" lower than yours. As you suggest, I can weld a 1/4" steel plate on the top of the mount where the bolt passes through.
By the way, if your driveshaft is a bit short, I had a machine shop make up a 3/4" spacer to go between the drive flanges where the driveshaft flange bolts to the pinion flange on the differential. There was a vibration at speed in this car that felt like a U-joint problem. The U-joints were OK so I hypothesised that maybe the front splines on the driveshaft were not sufficiently engaging those of the 3rd motion shaft and I was getting a little arcing out at the front U-joint. At the same time, I discovered a bulge in one of the rear tires. Problem solved - but it was probably the tire.
FWIW,
Allen
I had a new driveshaft made up. I hypothesize that the vibration you had (and I have to some extent) is due to the new lower angle of the transmission/engine. I raised mine as far as I could so the output shaft angle was as close as possible to the differential pinion angle, but there is still a 6 degree difference. That difference is enough to cause a vibration. You can get shims for the rear leaf springs to correct the pinion angle since there's no room to correct the output shaft angle. I'll be experimenting with that this summer to see if it helps.
I think you are right on that the pinon angle difference is causing your harmonics. Wedging or relocating the spring pads should cure it. I would advise welding the wedges to the spring pads once you are satisfied as I have heard of them spitting out (yah, on high torque 4x4s but why take the chance?).
I like th etype that has a round hole in the center, versus the slotted type. Then there's no way they can get spit out, even if the U-bolts loosen.
Re the drive shaft, are we saying that the increase in angle due to the drive shaft being slightly shorter due to the 5 speed is likely to create a vibration?
The variation between the pinion angle and the transmission output shaft angle may cause a vibration since the transmission needs to be mounted slightly lower than the original. For a good description on driveline angles, read the "Single Cardan Measurement" section about half way down the page of this website:
http://www.4crawler.com/4x4/CheapTricks/Driveline-101.shtml
With a Datsun setup, there will be approximately 6 degrees variation between the output shaft and pinion angles. A 5 or 6 degree shim set will get you back in range with stock.
On my previous Magnette (with the same Rivergate/Datsun conversion) there was no vibration at all. I used the original Magnette driveshaft on that car, only reaming out the front yoke to accept a Datsun U-joint at the front. My current Magnette has the same driveshaft - so if it's too short in one car, it must have been too short in both. So much for my own "too-short-driveshaft" theory.
Jeff, I'm uploading a picture of my transmission crossmember bolt-holes. There are two sets of holes about an inch or so apart. They seemed very clear in the view-finder, but they're pretty difficult to see in the picture. I know they're real because I turned a bolt into one of them. My crossmember was bolted into the rear-most set of holes - if yours is bolted into the front-most, that would explain at least some of the difference between your crossmember and mine.
I'm presuming that both sets of holes are original. They both look like they were installed by the same technique.
Cheers,
Allen
Let's try that again. I think the holes show a bit better in this photo.
Not much better, is it...
I'll try to get a better picture before Monday. I'm gone tomorrow.
Cheers,
Allen
I understand from the description. I figured that was the issue, although by looking at our pics I would have thought the holes were further apart. Yours mount look perfectly centered in the plate. Mine (the welded part) is set toward the back of the car further, so I must be using the front pair of holes? Just as an educated guess I think we're within 1/4" of each other on layout considering the bolt hole spacing. I'm really glad to hear there's an explanation for the differences!
My ZB has 2 sets of bolt holes where the bracket goes. The rear ones worked out fine for my Toyota trannie. I,ve got no idea why they where put there when it was built but I,m glad they did.
Maybe it something to do with automatics?
Andrew,
' Sounds like you have a Dellow kit, right? I've just exchanged some e-mail with Malcolm Robertson about this. I'm just wondering how it compares with the Rivergate/Datsun set-up that Jeff and I are dealing with and the Hi-Gear/Sierra kit that Moss sells here in North America. I'd like to hear from you regarding your impressions of the set-up. What engiine and rear-end are you using with it.
Jeff,
Many thanks for the link on drive-line angles. I'll have to read it more carefully before I fully understand the differences in shaft velocity due to mismatched angles, but the link explains another source of vibration that would never have occurred to my poor little geometrically-challenged brain. I would have presumed that the optimum would have been with the pinion in line with the driveshaft - but that could not remain constant as the rear springs flex, whereas a pinion parallel rather with the third motion shaft would make for a constant relationship. Had I seen it before my last series of posts, I would have written something else! However, we posted so close to the same time that I didn't see yours until after I posted mine - like -- just now.
Cheers,
Allen
Hi Allen
Mine are not installed in the car yet. What I have is a 5 bearing B motor matched up to a Toyota T2 5 speed transmission from a Celica. I found quite a bit of confusion from Toyota spare parts people (lack of knowledge) re these gearbox's and I think it was because they are from the 80s or there abouts. I have used the Dellows kit and it is good. I had no trouble putting it together. The only thing he did'nt supply was the rear gear box bracket so I made my own. Jeff Dellows is the guy to ask for if you where to ring them. He's the father and good to deal with. I think I may have read some where that Malcolm had a rear bracket from them which they dont appear to make now. The Celica over here was a 2 door that was produced here for around 20 years in various styles. It was pretty popular here and pretty tough. Hope this helps.
Andrew,
It sure does help. I think we have these gearboxes here. We too had Celicas for many years - they were very popular. ' Think they switched to FWD in '85. If the T-2 or T-3 boxes you and Jeff refer to are the same as the T-50, then we have them. I haven't actively searched yet.
Many thanks!
Allen
The way to tell which one it is is to count the number of splines on the rear out put shaft. I will try and find some paper work on this from Dellows
Andrew,
Before you go out of your way, Jeff did send me this information, so I already have it.
Many thanks anyway!
Allen