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MG TD TF 1500 Rear End Conversion Questions BBS discussion at MG-Cars.info
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MG TD TF 1500 - Rear End Conversion Questions
| Inquiring whether anyone knows the torque value to secure the crown wheel attaching bolts? Fitting up the MGA 4.3 ratio conversion pinion has raised an issue today. I found that to fasten the Flange Pinion I had to install a spacer between the nut/washer and the flange. For the spacer I used the center of a used front pinion bearing after removing the rollers and reducing the OD. All the literature and other posts on this subject do not appear to mention having to do this. |
| G Evans |
| Hi G I have mine in bits just now waiting for the pinion thrust washer to be machined. I have done some quick measurements, yes the MGA pinion is longer by about 5mm but this is compensated by the MGA universal joint flange being longer by the same amount. I know you are going to get angry now but you did remember to put the pinion thrust washer back between the inner bearing and the pinion gear. If you want I can do some more accurate measurements. Hope you can work it out. Barry |
| B Bridgens |
| G/day Barry Yes mate the pinion thrust washer is in place which I linished to 0.094, I have resolved something like 16mm by installing the spacer. I am wondering whether my troubles are related to the fact that I didnt replace the inner pinion bearings which were in the diff originally. The inner bearing cone is a 3188S not the 3188 recommended by Dick Lunney. I have had no trouble setting the pinion bearing preload.I will have to investigate dimension differences between the 3188S and 3188 bearing cones. |
| G Evans |
| High G I think the only difference between the two bearings is the fillet radius the S is .060" and the non S is 0.030". I don't know if such a small difference would give the problem you have. 16mm is a big difference, there must be a problem somewhere. Barry |
| B Bridgens |
| Hi G Using the later (MGA) ring gear bolts not early TD ones the torque value is 516 inch pounds. It's not clear to me about your pinion flange spacer issue. Usually there are only a few threads showing after torquing the nut and lock washer. I have seen a pinion flange that had been shortened for some unknown reason. I wouldn't think 5mm could be bearing related. 5mm is a lot of difference there. Pictures would help. Dave |
| Dave Clark Arizona |
| I had my rear end converted over to the MGA 4:3 ratio. Does anything have to be done to the speedometer drive gear? Will the speedometer still read correctly? |
| Michael O'Brien |
| Michael, the speedometer on the dash will need to be re-calibrated. If you look at your gauge it is 1525 turns to the mile for the TF stock rear end ratio. Lowering it to 4:3 without calibrating, you will have incorrect mph and miles. Contact http://www.nisonger.com/ and they will give you instructions before sending your gauge in. |
| Frank Cronin |
| Or fit a speedo correction gearbox. Regards Declan 
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| D Burns |
| Hi Dave I thought you had to use the TD bolts in the TD crown wheel carrier the MGA ones aren't BSF. Barry |
| B Bridgens |
| Barry, Early TD axles were BSF, sometime during the production they were changed to UNF. If your wheel studs are UNF then the axle is also UNF. John |
| J Scragg |
| Hi John Didn't know that, thanks for the info, will check mine in the morning. I have wire wheel conversion on my TD. Barry |
| B Bridgens |
| Barry, Looking through my documents I found that the change was made at TD 12285 Dec 10 1951. The problem is that there is no guarantee that you still have the original axle on your car. John |
| J Scragg |
| Hi John I just bought a second hand back axle to change back from a poorly installed MGA rear end, part of a wire wheel/final ratio change done by the PO. I have refurbished the axle and installing the 10/43 diff from the MGA axle, I have purchased new drums, brake shoes and WW hubs. I don't know the age of the TD axle that's why I need to do a check. Barry |
| B Bridgens |
| Michael - Contact Butch Taras a:mgyowner@yahoo.com He can make a ratio box for you. He did one for our TD and it works great. Cheers - Dave |
| D W DuBois |
| Thank you all for your info. |
| Michael O'Brien |
| OK this is beyond my powers of reasoning maybe someone has the answer. Image 1 Pinion exposed spline after fitting pinion flange Image 2 To follow 
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| G Evans |
| Image 2 Partially assembled pinion with spacer to facilitate fitting nut and washer. The Spacer length and shims provide a bearing preload of 8 inch pounds when installed in the diff housing. Incidentally the Crown Wheel Fastening Bolts are the same thread on both the supplied MGA Crown Wheel and the original TF Crown Wheel. There is a suttle difference in the length of the bolts. Best reference I could find was to torque the Crown Wheel Bolts to 55/60 foot pounds. I leave it to people who have considerable more experience with these cars to ponder an explanation. 
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| G Evans |
| G, It looks as if your flange is too short, the overall length should be 2 3/8" (60.3 mm) The one I have came from an MGA and it is this dimension. John |
| J Scragg |
| I would also think it is the wrong flange. This is what it looks like and I measured 62mm. Regards Declan 
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| D Burns |
| Hi, I am not home, but if you read Barry Jones book it has a chart for the different axel ratios vers old and modern tyres. From memory a 4.55 diff with 165/80SR15 tyres, the speedo is correct, against 5.125 with original crossplys. So depending on your tyres you may not need to get the speedo recalibrate. And, yes your drive flange looks to short to me. Regards Bernie |
| B W Wood |
| G, Could your flange be from a TD/TF? I don't have a spare one free to compare. This has jolted my memory, I read somewhere that if an MGA CWP as replaced the original T type gears then the prop shaft needs to be shortened by about an inch. Can anybody confirm, or otherwise this information. John |
| J Scragg |
| Hi John Here is pic of a TD flange. I thought that the number of splines was different MGA to TD/TF.It certainly looks like TD/TF flange. Barry 
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| B Bridgens |
| Thanks for the comments fellas. I dont believe the issue is the exterior length of the flange as when it is fitted in the housing it protrudes the same amount as the original TF one did. The issue is the depth of the bore where the nut secures it to the pinion. Definitely differences in the spline patterns between MGA and TF pinions. I will pull out the flange again to fit the pinion seal and measure the flange length. |
| G Evans |
| Hi Graeme, the MGA pinion has longer splines than does the TD and the end of the splines sticks out further when the MGA pinion is put in the TD housing in place of the original pinion. The flange itself is longer on the MGA but the inboard end is at the same position as the TD's. This results in the driveshaft end of the flange being somewhat further toward the front of the car if the MGA flange is used with the MGA pinion. To counteract this I sent a flange from a Magnette which is the same length as the one on a TD - this would put the end of the flange at the correct position for the driveshaft. Unfortunately I did not realize the splines were lomger on the MGA flange than on the Magnette and thus the MGA pinion splines stick out too far in the Magnette flange. I can send down an MGA flange and possibly you may then want to deal with the driveshaft length. Cheers, Hugh |
| H.D. Pite |
| Hi Hugh, you have totally solved the mystery I nearly contacted you from the outset however did not want to trouble you. I had an idea that perhaps the pinion flange you supplied came from another model MG, had no resources to determine that the Magnet had the same spline configuration. What you provided was a clever solution to having to shorten the tail shaft. Unless your opinion differs I am happy to run with the Magnet pinion flange you supplied. Fitting a spacer to address the additional spline length so the nut will clamp does not appear to be negative engineering practice. I hope others gain some knowledge from this exercise. |
| G Evans |
| Now that is confusing. I have not heard in any conversion story that the driveshaft would need to be shortened ??? Rgds, Mike |
| Mike Fritsch |
| Hi I am with Mike, as far as I have read an MGA flange fitted to an MGA pinion in a TD/TF rear end is a direct link-up to the prop shaft. I have done some quick measurements on my pieces prior to final assembly and this seems to be the case. Barry |
| B Bridgens |
| If you peruse the archive there are considerable posts asking whether drive shafts need to be shortened after installing MGA rear end components. Reading the posts has left me with no clear determination however I highly regard Hugh's MG experience. The article by Dick Lunney makes no mention of this being necessary. I am physically looking at the components that I have to hand and can see this would be necessary if the MGA pinion flange was longer than either my original TF or the Magnet items. To resolve this issue dimensioned drawings of both pinion flanges are required. I will measure and draw the pinion flange that was originally fitted to the rear end of my TF be nice if someone who has a MGA item to hand did likewise. |
| G Evans |
| G Evans, Here's my drawing of the flange. Hope it helps. I have added the spacer and shim details for reference. Regards Declan 
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| D Burns |
| I have added the splines. Declan 
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| D Burns |
| Hi Declan You are just showing off now with those hasty sketches. Barry 
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| B Bridgens |
| Whether you need to shorten the drive shaft depends on the car. Manufacturing differences, wear, etc. The only way to tell is to put the diff in the car, put the car back on the ground and then reach under the car and lift the drive shaft up to the pinion flange, there should be at least 1/2" clearance between the pinion flange and the drive shaft flange with the drive shaft pushed all the way forward. If less than 1/2" take the drive shaft to a drive shaft re-builder and have them shorten it by 1/2" and re-balance. Check the u-joints while you have it out. Butch |
| R Taras |
| I received my MGA Flange from Brown & Gammons today. Measures (rough only, with normal meter) from the bottom: Overall 62mm -bottom Flange 10mm -next ring 15mm -next ring 15mm -top ring 22mm (incl. the small hump) Depth of splines from the top end approx. 46mm Fits very well with Declanīs drawing, just is missing the dust cap. Rgds, Mike 
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| Mike Fritsch |
| Graeme, the MGA flange is approx. 10 mm longer than the one on a TD or a Magnete. Its face is therefore toward the front of the car by this amount more than would be originally. Perhaps the sliding splines on the driveshaft will accommodate this. Hugh |
| H.D. Pite |
| Many thanks Declan for the very professional drawing of the MGA Pinion Flange. Time permitting I will sketch and dimension the TF equivalent and post details. A precis of this long winded post is: Hugh is absolutely correct in his conclusions, the overall length of the TF Pinion Flange at 52mm is exactly 10mm shorter than the MGA equivalent. Pending on the factors that Butch has identified you may or may not have to shorten your tail shaft after installation of a MGA Pinion Flange. I hope out of this exercise the conjecture surrounding the necessity to alter tail shaft length has been resolved. There is the necessity for owners to factor in this additional cost if they are contemplating altering their vehicle rear end drive ratio. |
| G Evans |
| Today I am on the final assembly of the diff conversion into the TF and things are not looking good. Easy to be wise in hindsight, using the Magnete pinion flange resulted in the clamping nut,after installing a spacer to deal with the longer MGA pinion spline length, protruding past the flange face. Did not even consider the cavity on the tail shaft flange would not accommodate this although the tail shaft is the correct length. It is a case of "return to start do not collect $200", until I remove the pinion nut I cant tell whether I can reduce the thickness of the spacer so the nut does not protrude so far. There is a little ray of sunshine that might assist, a very thick spring washer is fitted between the nut and the spacer. Hugh I will Email my findings I may have to revert to using the MGA Pinion Flange. Graeme |
| G Evans |
| Graeme I followed the instructions in the Virgin Rear End Conversion article (on the web) & also read Carl Cederstrand's Crown Wheel & Pinion Interchange. I used an MGA pinion flange & sourced the 4.3 crown wheel & pinion & shims etc from Cambridge Motor Parts in England. As I didn't have the necessary equipment Craft Differential here in Sydney did the assembly. I've fitted the drive shaft & there are no shaft length issues. I loved the way the M.G. Car Club of Atlanta approached the task involving a few other Chapters & conducting a rebuilding workshop where 5 rear ends were built at the same time! Owners supplied the parts which had been sourced in advance & the clubs provided the expertise & manpower. Just shows what can be achieved & what M.G Car Clubs really should be all about! Cheers Peter TD 5801 |
| P Hehir |
| Peter Yes mate the instructions are clear and concise, a great effort on the part of the people involved. I followed their instructions to the letter and everything went fine except for the fact that Hugh was attempting to save me some grief if the tail shaft happened to be one of the ones that had to be shortened. Since my previous post I removed the pinion nut and found the length of the pinion thread also can not be accommodated in the cavity of the tail shaft flange. When I receive the MGA Pinion Flange I will repeat the build process. I believe I will be up for the cost of modifying the tail shaft as another 10mm on the length of the flange is probably going to give me grief. Ho hum, "life is not meant to be easy". |
| G Evans |
| Graeme, Could you check to see if the sliding splines will accommodate the MGA flange? Can you measure the depth of the cavity on the TF drive shaft output flange. I would try and avoid having the drive shaft modified. On a similar issue but relative to the 5 Speed Sierra conversion. Hi Gear engineering also mention a similar problem and they mention on there instruction sheets that the new propshaft which is supplied with their kit can collide with the pinion shaft on the TD/TF. Apparently the cavity will in "certain cases" not accommodate this. They recommend grinding down the pinion shaft a few threads. That I don't like at all. I have no chance to measure it all up at the present. Regards Declan |
| D Burns |
| Hi Declan The depth of the cavity on my original TF Drive Shaft Flange is 18mm measured from the face that mates with the tail shaft flange. From where I am at present it appears there was no intention for the pinion nut or shaft to protrude into the cavity of the tail shaft flange. I am optimistic this is all going to resolve itself when I receive the MGA Pinion Flange from Hugh Pite. I had my tail shaft custom made to address the fact that the PO had fitted a TC gearbox in my car, I wont be happy to have to modify it. Thanks Graeme |
| G Evans |
| Graeme, I measured 18.5mm on the MGA pinion flange and have updated the drawing accordingly-so a collision is in your case highly likely. When I just hand tighten the MGA pinion nut and washer, and no MGA bearing spacer fitted,the pinion protrudes beyond the flange by up to 2mm. It would need to be measured with the bearing spacer fitted for accuracy. The question is -is there enough sliding movement on the drive shaft splines to perhaps accommodate an 85x57mm (non standard size) thin spacer between the pinion shaft and drive shaft. The spacer could be drilled to the flange PCD. This might be a better way to go rather than grinding the pinion. Regards Declan 
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| D Burns |
| Ok Finally had time to sketch the TF Pinion Flange. Hope this assists in making a clear debarkation between this and the MGA equivalent. Graeme 
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| G Evans |
| I am a member of the 'Atlanta" Group (Southeastern MG T Register). We converted over 80 rear ends using the MGA flange, ring and pinion and spacers. We never had any of the flange problems above or required a drive shaft to be shortened. BUT we used only the MGA flange, spacers and nut that come on the pinon from the MGA chunk. ( a new nut and lock washer from Moss was always used in the final assembly) It must be that the wrong flange is being used. The only problem we encountered was in fitting the 4.55 ring and pinion from Moss ( spacers and thread problems) Don Harmer |
| Don Harmer |
| I had a comment from a fellow TD owner who had his rear end rebuilt by an expert, but reinstalled the axle himself. He had the same problem with collision of the pinion nut with the drive shaft flange. He filed down the pinion nut (and maybe the pinion end???) and so made it fit. Canīt have been too much (the nut is not that wide) but enough that the flanges did not go together. Since then, heīs a happy camper... If more details are needed, I can ask him for more specifics. Rgds, Mike |
| Mike Fritsch |
| Hi Just received the pinion shims that I needed to get the correct pre-load on the pinion shaft. After set-up I measured at the flange, the nut does not protude at all, the pinion shaft extends 0.65mm beyond the flange face. This protusion will easily be accomodated in the propshaft flange which has a hollow section 1.6mm deep. Now crown wheel pre-load and backlash. Barry |
| B Bridgens |
This thread was discussed between 30/11/2014 and 11/12/2014
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