transmission noise

[Troy35]

When I bought my Jeep, just a little less than a month ago, the Transmission made a little noise on the test drive. It only happened when I let off the throttle in forth gear. The PO said that it has made the noise forever and it's never been a problem. I drove it home about 70 miles and no change. I got home and changed the fluids in everything. Unfortunately, there was water in the Transfer Case and tranny. I filled everything with the appropriate gear oil to the correct level.

Now as I continue to drive the noise appears to be getting worse. It's louder in forth gear and a little noisy now in third.

Two questions:
1. From reading on here it sounds like I have a bearing going out, correct? I know it is impossible to diagnose a problem over the internet, but does this need to be addressed right now. If I have to get into the Transmission right away I'm going to hear about it from my wife.

2. Is there a different gear oil or additive that the PO could have used to quiet the noise (besides water) or do you think I'm just lucky and the problem is worsening quickly for me.

Thanks!

 

[Torxhead]

I would try a heavier gear oil, then go talk to the wife.

 

[FiNorman]

I would try a heavier gear oil, then go talk to the wife.

I know next to nothing about transmissions.... I would try heavier gear oil only because Torx recommended it, and avoid talking to the wife.

 

[Troy35]

Ok, thanks guys. I'll switch it out to heavier oil. I'm gonna get the, "You just bought that thing and now you have to do WHAT?!" if I pull the tranny right now. I know it's a bandaid. I'll post updates when I get into it. It's a weird noise to me because it's only when I'm off the throttle and coasting.

I'm also curious why it has a T-98 . I thought that the '74 came with a T-18 , but it has T-98 stamped right on the case. Was that a common swap at all. I know that the T-98 has a real low first gear.

 

[Torxhead]

The T-18 was the new and improved version of the T-98 .

 

[Troy35]

Yes, so it appears the PO took a step backwards in regards to the tranny swap. It's not possible that my '74 came with a T-98 , is it?

 

[FiNorman]

Ok, thanks guys. I'll switch it out to heavier oil. I'm gonna get the, "You just bought that thing and now you have to do WHAT?!" if I pull the tranny right now. I know it's a bandaid. I'll post updates when I get into it. It's a weird noise to me because it's only when I'm off the throttle and coasting.

I'm also curious why it has a T-98 . I thought that the '74 came with a T-18 , but it has T-98 stamped right on the case. Was that a common swap at all. I know that the T-98 has a real low first gear.

which noise bothers you more... 4th gear or the nagging "I told you so" tone. I'll crawl through broken glass before picking her breaking my chops. It's a personal choice.... remember the jeep you can park and turn the key, the other????

 

[Troy35]

HAHA, truer words were never spoken sir! You understand my dilemma.

 

[FiNorman]

"The T-98 was used in the jeeps up thru 1971 I believe and the T-18 was used from 1972 till 1979 with the exception of the J-20 p/u wich still used it thru 1983. The big advantage of the jeep T-18 is it's basically a bolt up to any 1972 to 1979 jeeps."
Bob

from another site.... also you can use the vin to distinguish the original number of speeds.
Vehicle Identification Number (VIN) 1971-1986 Jeep CJ<
are both a 4 speed?

 

[FiNorman]

This may answer the mystery.

"The T-98 Transmission would slowly be phased out in favor of the improved T-18 Transmission . The T-18 Transmission would offer a number of upgrades over the T-98 . There is often much confusion and misidentification among the T-98 and the T-18 . It would seem logical that a Transmission stamped with “T-98 ” be a T-98 ; however, this is not necessarily true. Some Jeep T-18 transmissions used the exact same top covers as the T-98 . The stamped “T-98 ” top cover is where most misidentification occurs. It can pose confusion for those seeking specific gearing options and spare parts. Identification is also imperative when using one of our adapters do to input shaft and output shaft differences. We have put together a more detailed technical section on conversions with the T-18 and T-98 . Please review this section for a better explanation on the differences, commonalities, and adaption options for these often misidentified and misunderstood transmissions."

Jeep T98 | Tech Vault | Advance Adapters

 

[FiNorman]

"Identification
The T-98 's progeny, the T-18 , used the same top cover as the T-98 up through 1979. Many individuals assume they have found a T-98 upon seeing the "T-98 " cast into the top cover, when in fact, it is a T-18 .
The only way to rule T-98 out from being a T-18 is to open the top cover and count gear teeth. The T-98 will have a 43 tooth first-reverse sliding gear (the rearmost mainshaft gear, spur cut) and a 17 tooth cluster gear (also spur cut).
The T-98 's mainshaft features a smaller pilot tip than the T-18 and has needle roller bearings under second gear.
Jeep T-98 's may feature a casting code of 1301-174-6117. Some may have a T-18 -1P WG Division cast into them."

The T98 Transmission - Novak Conversions

 

[dschwab]

My '75 made a grinding noise while coasting and anytime I had the clutch in when I bought it 7 years ago. I changed out the fluids with a synthetic hoping new oil would fix it and it did not. I had the "Ill fix it when it breaks" attitude and 7 years later she was still going. Pulled the Transmission out last month since I am doing a frame swap and the throwout bearing was toast. hope this helps with the decision making process.
And good luck with the wife... I am ordering all new suspension next week and I got an earful for that.

 

[Troy35]

I was gone for a few days but I really appreciate the replies. I'll have to do some checking to confirm that I most likely do have a T-18 .

I'm also just going to run it for the time being. It sounds like catastrophic failure is not in my immediate future.