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1965 4Speed Transmission Leak

My 4 speed transmission is leaking oil between the transmission and the bellhousing. I understand that its probably the shaft seal underneath the input shaft. Does anyone know how to fix this without pulling the transmission out. I understand it can be done! Andy

Submitted by: Andy Bedoian


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4 speeds don't have a front seal. Only an oil slinger. Counter shaft in case not sealed (someone else said that) too much oil in the case or the WRONG oil in the case Richard Rogers on 1/16/2019 6:37:06 PM
Thank you all for your thoughtful reply's. Actually an old timer told me a process I'd like to share with you. Depending on the severity of the leak (usually caused by racing and hard use) a small leak can be fixed by backing the transmission back on it's tranny to bell-housing bolts, (might need to get four one inch longer bolts) to gain about 1/2 to 3/4 of an inch clearance between the tranny and bell housing. Next drain the oil if you have not already done so, get a butter knife and with some brake clean on a rag, wipe around the shaft to get all the oil residue off. Then apply some good quality black RTV silicone seal and let dry. Bolt the tranny back into place, refill with oil. Done, well hopefully done. I'll let you know how that works out if the first suggestion doesn't do the job. Thanks again all. Andy Andy Bedoian on 1/29/2018 1:26:41 PM
Try Blue Devil Manual Transmission Sealer. David Grimshaw on 1/28/2018 4:12:37 PM
It could be the case where the cluster gear shaft is pressed in. Thats what it was on my M-21 box which I rebuilt using a new alum. housing. To do this see the shop manual. Glenn Hanna on 1/26/2018 10:27:56 PM
Are you sure it's transmission oil and not engine oil? Smell it to be sure. Gear oil has a pungent smell compared to engine oil. If it is the front transmission seal, the proper way to fix it is remove the transmission and install a new seal. It's an easy seal to replace. I would not recommend an additive sealer since that might affect the synchronizer rings. If it turns out to be engine oil, rear main bearing seals are quite a bit more involved to change. Either way you have to remove the transmission. Good luck with the repair. Jerry Rebman on 1/26/2018 5:28:15 PM
It's the front shaft seal, and I know, no other way to fix it other than yanking the trans. But my buddy had the same issue, a slight leak. So, he drained the oil, replenished it, but added an engine oil stop leak to it, and 3 days later, it stopped. Must have lasted a long time, he never spoke about it. Mike Posted by Administrator on 1/26/2018 4:34:21 PM

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