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MG TD TF 1500 - Bolts securing XPAG bellhousing?

I am attempting to fit a Hi-Gear 5 speed conversion into my TF1250. Committed now as the chassis is cut to accept the new bolt-in gearbox support.

Today I finally managed to get the (very nice) Hi-Gear bellhousing aligned and to fit nicely onto my XPAG block. All going well until I find the lower five bolts do not fit into the Hi-Gear bellhousing! They are a larger size (up from 13mm to a 15mm socket) than the upper five bolts!

My question, are there two bolt sizes for the XPAG block, or is this the "handy work" of a previous owner? My fault for not checking, but damn frustrating either way!

Kev S
TF6288


K Simonsen

Sorry, but a picture is worth a thousand words! Hmm! Should have been upside down, coming from Australia.

Lower half, lighter colour, where the "offending holes" are. The replacement Hi-Gear gearbox support is a very nice piece of work.

Kev S
TF6288

K Simonsen

Having fitted two of the Hi-Gear 5 speed conversions I would say it's the work of the previous owner. The reason I suspect that is the case is that the lower bolts go into the sump and being aluminium are prone to the thread being stripped. Have helicoils been fitted? Or did they drill and tap to accommodate a larger bolt?
JK Mazgaj

Just swapped my gearbox, all bolts are the same, 8mm x 1mm, watch the length.

Peter
P G Gilvarry

The Hi-Gear bellhousing is 3mm thicker than the original. Originally M8x1mm bolts were fitted. It looks like a modification was made by the previous owner as mentioned. Measure the depth to the flywheel before fitting longer bolts.

Regards
Declan
Declan Burns

I thought the High Gear kit came with the proper bolts. Yes/no?? The bell housing bolts on my TF are all the same size, must have been a POs solution for stripped-out threads for the subject car.
PJ Jennings

Hello, I have an XPAG which a previous owner had drilled all the bolts out to 3/8 NF in the pan where the bellhousing bolts up. I have installed 8mm x 1mm pitch timeserts into these holes which work perfectly with the threaded holes in my pan. The timeserts outer thread is 3/8 NF as well.
Kim Herford
W K herford

The threads all round should be 8mm dia x 1mm pitch. They are not ISO threads, but they are SI threads, which were the original standard metric threads - they are very similar to ISO threads, but have different pitches for some sizes. Also, the original bolts had imperial heads, and a 13mm socket should not fit - but a 14mm socket will be a loose fit.

Regarding the block threads, a metric bolt with a 13mm head will be ISO M8, for which the standard pitch is 1.25mm. If these have been used the threaded holes may be damaged.

Regarding the sump threads, a metric bolt with a 16mm head will be ISO M10, for which the standard pitch is 1.5mm. Thus oversize bolts have been fitted, and 8mm x 1mm timeserts or helicoils may solve the problem. It may be worth experimenting with M10 tapped holes in a spare piece of aluminium.
R WILSON

Should have said, for the block threads, there is an ISO M8 fine, for which the pitch is 1mm. Although not common, bolts using this thread are available, so you may have them fitted.
R WILSON

The socket size is irrelevant. Only thread size and pitch matters. It appears the pan holes are larger. The original 1.0x 8 threads virtually always strip in the aluminum and someone likely drilled out and tapped to a larger size. You have two choices- 1) find the existing thread in the pan holes and appropriate bolts. Then drill out the bell housing to fit. Or Helicoil the pan back to original size and diameter threads. The steel inserts will never strip. There are other brands such as Recoil. Suggestion: search the archive for stripped pan bolts or something, as there are many threads in there about this. Last but not least- a bolt that is too long will either lock the flywheel/engine or make a really terrible screeching noise. I have demonstrated this before 😳😂. George
George Butz III

To remind you Kev the bolts to the sump -if not all, should have Loctite applied to ensure no oil leaks as per Hi-Gear instructions. This is because certainly one in particular enters the sump area.
JK Mazgaj

Perhaps I should have said;- The original SI metric bolts used by Morris had imperial heads.
Surely all the ten bolts holding the bellhousing to the engine go into the flywheel space, so how do they enter the sump area?
R WILSON

They do not enter the sump, they are about 2” away.

Loctite is to secure the fastener not an oil sealant. The originals and replacement kits have spring washers.

Peter
P G Gilvarry

Peter, I'm quoting from HI-Gears fitting instructions which explicitly refers to this point.
JK Mazgaj

Hi. MG friends. I agree with R Wilson.None of the bolts are entering the sump.
Thoralf.NORWAY TD 4490
Thoralf Sorensen (TD4490)

Kev, just a different topic but since everything is open now down there, maybe worth to consider to move the petrolline to the other side, further away from that very hot exhaust pot.
Huib Bruijstens

They may refer to the whole alloy thing as the sump, however the bit with the oil in it is at least 2 inches forward of where you are screwing the bolts into.

The bolts would have to through the flywheel to be near oil. I have swapped the gearbox twice, not a drop of engine oil leaked out.

Take a look at a side on view of the engine, the gearbox flange has no engine oil nearby, except the bit that has leaked out of the rear seal.

Peter
P G Gilvarry

I must apologise for my misleading remark about bolts to sump. On re-reading the Hi-Gear instructions I was reminded that it was in bolts to the GEARBOX where caution should dictate the use of Locktite. It was my memory that once again failed me.
JK Mazgaj

The original bolts into the Aluminium sump would have had Whitworth heads on the metric threads. A modern metric bolt will have a different sized heads. I ended up using standard metric coarse thread screws. As an engineer I prefer coarse threads in castings specially alum.alloy (and cast iron) saving fine threads for rotating or parts subject to vibration. I havent converted the majority of threads in the block tho.Unless you are very unlucky nobody will see them !




AP Jones

This thread was discussed between 29/11/2021 and 02/12/2021

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