T5/T4 Correct Fluid

[JMark]

Hello Guys

My CJ is coming along very nicely, 4.5" BDS lift, regeared to 4.56, ARB air lockers and a host of other lovely toys. Heck, i even resolved almost all of the oil leaks!

The question i have is what SHOULD be in the T-5 Transmission ? FSM calls for dextron, looks like someone put 80w90 in it and its leaking from the fill plug.

Thanks!
-JMark

 

[PaRenegade]

Based on my research I used Penzoil Syncromesh in my T-4 .
The FSM calls for 4.0 pints of AMC/Jeep ATF or equivalent labeled Dexron, for the T-5 .

 

[Rube83]

I've always used 80-90 with no problems. the issue with it coming from the fill plug may be that water has got into the system.

 

[Dan86CJ7]

the original part# supers to an NV Transmission fluid i get right from my parts dept. here at the jeep dealer.. thats what ive run

 

[hole]

Synchromesh

 

[wm69]

Here you go. Post #14 has a link to the Scrambler board where an analysis was done by a guy on the original AMC "fish oil" fluid that was used in the T-5 .

http://www.jeepforum.com/forum/f8/t-5-fluid-question-1926993/

In short, it is CLOSE to 90W oil, but not exactly. That is the BEST info I have seen in 20+ years of Jeeping as to what the "original" T-5 fluid was.

I would use some sort of Synthetic 80-90W oil if you're keeping the T-4 -T-5 .

I've been using 75-90 in mine since around 1994, but I'm planning a T-176 swap....good fluid doesn't fix a marginal Transmission .

 

[hole]

I had several quarts of the AMC redish brown fluid that replaced the original ATF sitting on my shelf for years. It was nowhere near as thick as 90w but not as thin as ATF. The PO of my 8 said the Transmission (T-5 ) was rebuilt and builder said to use 75-90w gear oil. The PO didnt seem to have any complaints, but he was eldery and never took the 8 out of the city limits. When I first got it, I had problems grinding 3rd to 4th under high rpms (enter freeway) and downshifting almost any gear produced grinding. After reading an article from a Transmission builder that specializes in BW T5s he recommends nothing but Synchromesh. I tried it and had immediate results, no more grinding on any shift up or down and reverse was even easier. I'll try and find the article and post it. It seems that many of us have had luck/success with a variety of different oils, which leads me to why? I could understand some differences due to climates, but it seems to be much more than just that.

 

[Tinman22]

Many people have used many lubricants in t-5s with different levels of success.
One of the biggest issues is the design of the T-5 and it's use of bushings rather than bearings under the gears and bronze syncros. Many shifting problems have been "cured" with syncromesh wich is a 5w30 with friction modifiers but may take a toll on the bushings. Calling tremec will get an answer of 50 w synthetic or 70 w synthetic such as shells spirax. Wich is the same lube required by eaton in our 13 and 18 speed truck transmissions rated at 2000 ft/lbs behind 600 hp engines pulling 120k lb loads. We have had pretty good luck with it.