What to look for in a transmission

[psimet]

So I have the drivetrain torn down back to the transmission. I do have to replace the input shaft due to switching to the single plate clutch but what else should I look for or inspect? Do I just pull it and tear it down and clean everything? If so is there a good guide for what to look for?

I don’t feel like just replacing everything “just because”. Thoughts?

 

[Marshall V. Daut]

If the gear teeth are worn to points across their tips instead of being flat and there is pitting in their faces, it's time to replace those gears. I disassembled a transmission last week, whose teeth looked good. When the cluster gear was pulled out, the long bearing inside was missing one roller from its cage. It fell out at the same time, broken in two. I have no idea how the transmission acted previously because I had not driven the car. My bet is that it was noisy because of the damaged roller bearing. I suggest that even if your transmission looks good upon a cursory examination, take it apart anyway to check for hidden damage or wear. It doesn't take long to disassemble a Model A transmission once separated from the bellhousing and the U-joint has been removed from the rear. Check the two main bearings for smoothness and replace the gaskets. Make sure the little spacer ring is still on the snout of the main shaft. This often gets forgotten when a rebuild has taken place.
Marshall

 

[nkaminar]

I am not the expert on the multi disk clutches, but from what I have read, the input shaft has to be replaced when switching to a single disk clutch. There may be other changes. Search the Barn Forum for information.

Marshall has some good advice.

 

[Gene F]

It looks fine to me. Swap the input shaft (bearing too of course), clean the thing up and go. I have seen way worse.

 

[Bigsnapper43]

If my memory is correct the case must be changed also.

 

[Keith True]

Yes,the case has to be changed unless you are capable of machining the bearing hole,and drilling and threading holes to hold the front bearing retainer/throwout bearing tube.You do know that you also need to change the bellhousing and pedals,right?

 

[Bigsnapper43]

I think the case must also be changed. That makes the input and the case ,Flywhell and pressure plate, clutch disc and throw out bearing necessary for this operation.

 

[psimet]

Yeah I had another thread about all of this. There seemed to be disagreement on the transmission case. I have another one.

Yes I have: flywheel, clutch, pressure plate, flywheel housing, pedals, throw out bearing, etc, input shaft, etc. still in process.

I still haven’t finished building the long block. Not much of a point in finishing things until I have everything done and everywhere I turn there’s something new. Was hoping to get away with existing housing. I do have another one so hoping that’s one I can repurpose.

 

[psimet]

Not the right side of the case but it’s the only picture I have with me. Maybe someone can tell from that. Otherwise I’ll grab a shot tomorrow at the shop.

 

[Mulletwagon]

Good time to change out the cluster and idler shafts for the O-Ring type. The throw out bearing and U-Joint are also good candidates for change if any wear is noted.

 

[ThirstyThirty]

If you can pull the trans and related parts, change input, then... I (me, too!) see no reason not to tear the entire assembly down, piece by piece, inspect and clean everything of everything to include the finite particles of crud that accumulate in any motor mechanical assembly's small spaces from many miles of use. replace what is worn or broken. look for any chipped teeth! done right, the reassembled assembly will be a source of pride and confidence!

a vs .

 

[nkaminar]

Psimet, If you can afford it, a Mitchell transmission with synchro on 2nd and 3rd is nice. You might be able to sell that transmission to someone who is restoring an early car with a multiple disk clutch.

 

[rackops]

I just took my transmission apart, inspected, cleaned, and replaced some of the parts. I watched George Bell's videos on YouTube and they were super helpful.

As far as a new transmission case, they're cheap and can be found in decent shape on eBay. I'd buy a single-disk case rather than trying to mess with the multi-disk case. Also, your input shaft is very different, so that will have to be replaced as well.

I'll take some photos later of the differences.

 

[katy]

Suggest you replace the front and rear main bearings w/new ones with a seal on one side. Put the "seal side" facing out.

 

[rackops]

Here are some photos of the transmission cases. The primer grey one is for a multidisk; the other is a single disk. There are enough differences between the two where it's worth spending $30-$50 to buy the correct transmission case instead of trying to get the multi-disk one to work.

 

[psimet]

Here are some photos of the transmission cases. The primer grey one is for a multidisk; the other is a single disk. There are enough differences between the two where it's worth spending $30-$50 to buy the correct transmission case instead of trying to get the multi-disk one to work.

As I mentioned above I have another case I picked up with a bunch of other parts.

Interesting for me to note is that my multidisk case has shaft holes the same size as the later case, not the large shaft you’re showing on yours. I did see there were effectively 3 variants. My car is a Sept ‘28 car so after the switch in shaft sizes it appears.

 

[psimet]

Just got to the shop and the other case I have is drilled and bored correctly for the single disc setup it looks like.

 

[psimet]

Psimet, If you can afford it, a Mitchell transmission with synchro on 2nd and 3rd is nice. You might be able to sell that transmission to someone who is restoring an early car with a multiple disk clutch.

I knew about their overdrive but I wasn’t aware until you posted this that they had a regular transmission with synchro. Project is already $$ for now. Between what I can find for a price and waiting 1-1 1/2 years I think I’ll just rebuild it as it was. I don’t plan on driving it a ton outside of short trips.

 

[psimet]

Good time to change out the cluster and idler shafts for the O-Ring type. The throw out bearing and U-Joint are also good candidates for change if any wear is noted.

I have to change the throw out due to changing to the single disc clutch anyway.

I pulled the u-joint and it’s one of the early ones that’s riveted together. I didn’t take many pictures as it seemed in decent shape and I didn’t realize there were 2 designs.

Also just checked and everyone is out of u-joints …. So…. Anything in particular I should check for in assessing the one I have? Doesn’t seem like there’s much is any play or backlash in it but looking for guidance here.

Took the pictures because I noticed the lock washer was completely flat and off center.

 

[Mulletwagon]

Some caution with U-Joints. The best ones are NOS USA made. My joint was bad so I ordered one from one of the standard suppliers. It was made off shore and had more play than the unit I was replacing. I was fortunate to locate an NOS unit from another Model Aer that answered my May Day. If your joint has very little or no play, and you csannot locate an NOS non-rivet type, certainly use what you have to get your ride back on the road but be on the look out for a quality replacement. Enjoy following your rebuild !