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T-Series & Prewar Forum

What Differential?

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skibum12g Avatar
skibum12g Silver Member Erik G
Clifton Park, NY, USA   USA
1952 MG TD MkII
1979 MG MGB
Hello,
My gearbox is in bad need of rebuilding. I've been hearing from folks that it might be cheaper to put in a 5 speed than to rebuild my 4. One thing though is it matters which rear end is installed. My car is a '52 TD MK II. But somewhere along the line, someone replaced the wheels with wire wheels. Is there any casting #'s or anything that might tell me what the actual differential is that's installed?
Thanks,
Erik



Erik

'79 MGB
'52 MG TD MK II

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LaVerne Avatar
LaVerne LaVerne Downey
Fruita, Colorado, USA   USA
1954 MG TF "Green Hornet"
1969 MG MGB
There should be some numbers stamped on the tube near the case but there might be a chance that it has already been changed. you might use this chart and see how it compares to what you get.

http://www.ttalk.info/RearGearInfo.html

For whatever it's worth , my 5 speed gearing is a fairly close match to the original 4 gears. Picking a gear set for the rear end opens up a whole nother can of worms about which one to choose. My advice is do the 5 speed and worry about the rear end later.

Declan Burns Avatar
Duesseldorf, NRW, Germany   DEU
I second that.
I had all the intentions of doing the 4.3 rear end conversion and made all the special tools to do it and sourced the CWP and bearings. When I fitted the five speed I was so happy with it that I left the rear end as it is.

Regards
Declan

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Buckdendave David Hill
St Neots, Cambridgeshire, UK   GBR
1954 MG TF
Yes, I fitted the Ford Type 9 gearbox and changed the axle ratio to 4.55:1. With an uprated 1250cc engine (Stage 2 ish) this combination works really well, with no problem at all in hauling top gear at moderate speeds.
To determine the axle ratio is easy. Put the car in neutral and jack up one rear wheel, then put a chalk mark on the the diff input side (drive flange) and the output side (raised wheel). Rotate the wheel and count the turns on both the wheel and drive flange - the more turns, the more accurate the answer. The ratio between the number of turns of the input flange and the wheel is double the answer that you are looking for (because you are rotating only one wheel, not two). If you rotate the wheel 20 times it makes the calculation simple.
Dave H

Ctwidle Chris Twidle
Reesville, Queensland, Australia   AUS
1954 MG TF
Hi Erik, my gearbox is currently away being assessed. It had a major rebuild a few years before it was taken off the road 40 years ago so I don’t yet know what would be needed to get it up and running again. I have already had a 4.55 diff put in as the original (probably 5.125 as it has original wire wheels) had broken teeth and it seemed like a good idea at the time and was much cheaper than a 4.3!

In case I didn’t have enough things to ponder, recent reading on here has suggested that there is a potential problem with harmonic imbalance variously stated as being between 3500-4000 and 4100-4300 rpm. I am beginning to wonder if the reduction of cruising speed rpm from the various diff/gearbox conversions is likely to result in the engine spending extended periods in the suspect range. It seems to be something of a coin toss between that and the increased rate of wear that comes with higher revs.

Decision pending....

Chris

peter14222 Avatar
peter14222 Peter Gilvarry
Buffalo, NY, USA   USA
I am looking at doing the rear end as the easier option, but would prefer 4.1 Vs 4.3 as I have a TF1500.

Looks like Dave Clark may be the best option.

Peter

Buckdendave David Hill
St Neots, Cambridgeshire, UK   GBR
1954 MG TF
Dave Clark's half-shafts are also an excellent choice.
Dave H

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Paul J Avatar
Locust Grove, ok, USA   USA
I had Dave make me a 4.1 rear and installed his new half shafts. My 1500 rebuilt engine is fine with this setup, I'm very happy with it! PJ


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peter14222 Avatar
peter14222 Peter Gilvarry
Buffalo, NY, USA   USA
Not knowing much about this, is it hard to install half axles, do I need to get bearings/seals?

I guess the wire wheel hub goes on after the axles are installed? Are the half axles different from wire to disc wheels?

Thanks, I need to get a blown up diagram of how to do this.

Peter

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Buckdendave David Hill
St Neots, Cambridgeshire, UK   GBR
1954 MG TF
Replacing the half- shafts is much easier than rebuilding the differential. In any case its worth taking a good look at them, because they have a tendency to fail from the splined end, where cracks can often be observed. You need to get a copy of the Workshop Manual - plenty come up on ebay.
Dave H

Hawkmonster Avatar
Hawkmonster Joe Policastro
Flagstaff, Arizona, USA   USA
Hi Peter

Reference your questions. If you buy a rear from Dave he will install the shafts. It is then a simple R and R and all you do is ship him your old one back. I suggest you not wait. Dave splits his time between AZ and WA. Winters in AZ and only does diffs while in AZ. He has a beautiful machine shop there. Real nice guy. He has sold his TF and is into Jags.

Most of the Flat landers here install 4.3 gears but your 1500 should handle a 4.1. I run a 4.55 in the mountains with a supercharger and upgraded head and compression.

By the way did you ever buy those luggage straps. If so how do you like them.

Joe

skibum12g Avatar
skibum12g Silver Member Erik G
Clifton Park, NY, USA   USA
1952 MG TD MkII
1979 MG MGB
As usual, you guys have been way more than helpful. Dave H - where did you get your Ford Type 9 from? Was it a straight hook up or did you need to do some work? I have an 8" clutch.
Erik



Erik

'79 MGB
'52 MG TD MK II

peter14222 Avatar
peter14222 Peter Gilvarry
Buffalo, NY, USA   USA
Yes, I did, since this photo I added some holes in the long strap.

Works very well, weather permitting I will be on a Club drive on Sunday.

Thanks for the lead!

Peter


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Ctwidle Chris Twidle
Reesville, Queensland, Australia   AUS
1954 MG TF
Erik, a few options for you to consider:

Hi-Gear engineering in the UK is the source of the kit for a popular T9 change but he is in his eighties and hopes to retire within a year or so. Lots of references on here. I believe he sometimes has gearboxes but they are getting harder to find.

If you are not in a hurry Vitesse engineering, also in the UK, are trialling an MX5 (Miata?) transplant in later MGs and are considering extending their range to include some of the T series. I believe either swap would require the removal of the crossmember to be replaced by an alloy casting and a purpose made bell housing.

Dellow Conversions in Aus have the parts for a Toyota swap but I believe that gearbox is even harder to find.

I am at least a year away from needing to fit a gearbox to mine and am still looking at options.
Chris

Buckdendave David Hill
St Neots, Cambridgeshire, UK   GBR
1954 MG TF
I bought my Type 9 gearbox from a private seller on the MG Octagon Club website, and also the Hi Gear conversion kit which makes the job easy. The best places to look for one are Ebay uk and Turbosport forums, parts for sale, etc. They do appear from time to time in both of these. Lots of gearbox reconditioning outfits around that know the Type 9 well, and a few do specialise in them. Some require a gearbox in exchange, but some don't. Look at people like BGH Geartech and First Motion Transmissions. I believe that any Type 9 can be adapted for our purposes but some variants need more parts than others.
Dave H

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