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MG TD TF 1500 - TF diff upgrade

Searched the archive using the above wording including variations but returned zero information. What should I use to see what has been discussed in the past please?
JK Mazgaj

What upgrade are you looking for? Bud
Bud Krueger

I assume you are looking to replace your 4.875 differential gears with 4.3 gears from an MGA diff? I suggest searching for "4.3 differential" in both archives, and you will be overwhelmed with the volume of materials in the archives.

The bottom line is that you need a complete MGA 4.3 pumpkin, and that while it is humanly possible to install it yourself using Carl Cederstrand's booklet and the Chicagoland MG club (I think) instructions, it is far easier to have one of the experienced guys - like Butch Taras - do the conversion.

Tom Lange
MGT Repair
t lange

All you really need is the crown wheel and pinion.
Dave H
Dave Hill

Dave I'm sorry to say you are wrong. You also need the pinion flange(the splines are different), the pinion bearing spacer(it has a larger Id and od) and the spacer that goes between the pinion head and the bearing(it has a larger od and id). Also the pinion nut is a different thread.

Butch

R Taras

Yes, that is so - I forgot the flange. The spacer can be fabricated and the nut (I needed several) obtainable off the shelf.
Dave H
Dave Hill

Bud, I'm simply reviewing what changes will help my use of the car without a complete competion engine rebuild. I was looking at the 4.55 modification which I believe is a more simpler "upgrade". I have incidently already fitted a five speed box.
JK Mazgaj

JK, there's little that can be accomplished by changing the differential ratio except going to a numerically lower ratio. All of those available ratios are from later MG differentials and do require serious reworking. Your 5 speed box already gives a substantial move toward easy cruising. If you're thinking about performance boosting you might want to think of going to a roller cam system, such as available from Len Fanelli (see http://www.ttalk.info/Fanelli.htm). The archives should get you a good bit about the roller cam performance. Bud
Bud Krueger

JK - in terms of installation,the 4.55 is the same as the 4.3 - both require a certain degree of knowledge and experience. Your 5th gear is already an overdrive; I would consider carefully your goals and style/speed of driving. You already have a 4.875 and o/d, so a 4.5 would be a small step.

My ideal installation to run on American roads with a certain speed-confidence - is a 4.3 diff, a supercharger and a 5-speed. If you have no plans to rebuild or up-grade your engine any time soon, I would be very sure the present set-up is not adequate. Over here it costs about $1,500 plus the gears to make a diff gear swap.

Tom Lange
MGT Repair
t lange

JK,

I have exactly what Tom Lange suggests plus roller cam and rockers and unless you plan to blast up and down the A4 you will almost never get into 5th gear. I have driven all over the highlands, to the Orkneys and Mull and except for some few long straight stretches of road I could never envision using 5th or even 4th in some areas. I would imagine the same would apply to Cornwall although I have not yet visited my ancestral village of Luxulluyan (O'Bryan, Bryan, Bryant etc)

Your present setup with the 5-speed should give you the biggest bang for the buck.

Jim
James Neel

You can use the crown wheel and pinion from most of the 1950s/60s BMC cars e.g. Austin Cambridge, Morris Oxford, Riley 1.5 etc but don't ask me about ratios. I fitted an alternative rear end into a TD I owned some time ago and the new owner later asked me if I still had the original parts. He had had problems on a tour in the Lake District. I have recently completed a tour of the Scottish Highlands in my TF which has a 5 speed box and the car coped splendidly.

Jan T
J Targosz

The above is all good advice. Cornwall is not much like the Highlands, more a case of driving in the bottom of narrow ditches at times I would say, some quite steep down to the sea. For local advice you could probably do yourself a favour by speaking to Roger Furneaux (Devon), who probably has the means, or knows somebody who can do anything you want.
Dave H
Dave Hill

You do not want to go to a much higher ratio if you have a 5 speed box. Your present set up will be giving you around 18mph per 1000 revs. I have a 3.9/1 diff with a standard gearbox which gives 20mph per 1000 revs which just a tad too high. I have had to snap change into 1st a few times on road rallies in North Wales.
Ray TF 2884
Ray Lee

I have a 4.1 in the TF with a stock transmission and it works very well, but it's a rebuilt 1500 and has plenty of pep. I wouldn't recommend it in anything with less power. PJ
PJ Jennings

If the five speed gearbox is the Ford type 9, in which the fifth gear is 0.82:1, then with a diff ratio of 4.875:1, the over-all fifth ratio becomes 3.9975:1, or simply 4:1.
You will need a lot of power, or more important, torque, to pull this ratio.
R WILSON

Yes, but the point is that fourth, at 1:1, remains the same overall ratio as the original gearbox in fourth / top. This makes 5th a nice overdrive gear when running along on the level. I use it all the time and the diff is 4.55:1. Engine is 1350cc and stage 2.
Dave H
Dave Hill

The real issue, is finding a 4.3 or 4.1 CWP. They're getting VERY hard to find now. Autogear had a batch made abt 10 yrs ago, and those went quickly. Today, they'd likely not be competitive. Abt 2 yrs ago, I approached a local machine shop with the right machinery to cut CWPs, and was quoted $1,200 CAD per set in batches of 20, and I'd have to post $15 big ones to cover the set-up costs.

I have to agree with comments about a 3.9. Certainly living in the Rockies, it would not be in the least bit practical. A 4.2 from an MGA MkkII is good, but the 4.3 set-up is still the best all'round solution for our standard, 4-speed gearbox.

I have a couple of 3.9 pumpkins ... $250, if anybody is interested.

Gord Clark
Rockburn, Qué.
Gord Clark

Could I just remove the TF 1500 rear axle and install my spare MGA 1500 banjo rear end in its place? Anything special to consider?
thanks, Tyler
(PS: Don't tell my wife).
C.T. Irwin

I've no direct experience but understand there to be at least two major issues. Firstly the suspension mountings need to be moved. Secondly, the wheels and hubs will be different from the front (and the spare). No doubt others will jump in.
Dave H
Dave Hill

Hello Tyler. The other issue is the emergency brake on a t series is attached at the front of the backing plate and the mga attaches to the rear of the backing plate. As mentioned the spring mounts need to be cut off, re-located and welded back on. The wheel issue applies if you don't have wire wheels. Also you may need to shorten the drive shaft. It depends on the car. This conversion has been done in the past. Putting the Mga gears into the Td/Tf housing involves grinding the spacer under the pinion head to the proper thickness based on the factory tooling. Grinding the spacer between the inner and outer pinion bearing to give the correct bearing pre-load. Both those parts surfaces have to be parallel, I do that on my surface grinder. Then assembling the gears to the housing and grinding the carrier spacers to give the correct backlash between the pinion gear and the ring gear. If you have more questions contact me by email. I've done about 100 conversions over the years.

Butch
R Taras

Okay, So I'll gladly forget that idea. Thanks for the very quick responses.
By the way, there was a guy with a recent block (box) advert in Classic Motorsports magazine for 5-speed conversions for MGs (etc.). Can't remember his name, but I tried his web address and phone with no success. I think he inherited the business (buys quantities of conversion kits from England) from Butch White who passed away years ago. Does anyone have any info on him?

Tyler
C.T. Irwin

His name is Jim Hall of MG 5 Speed Company in Green Cove Springs, FL. Is ad is current in Classic Motorsports, but is he still in business?
Tyler
C.T. Irwin

Thanks all for your contributions. Looks like there is no real advantage to my present set-up and anticipated use.
JK Mazgaj

I have an eary MGB banjo rear with a 3.9 in it that will fit in a T rear and can't give it away.
PJ Jennings

This thread was discussed between 22/06/2019 and 25/06/2019

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