Dana 300 Gasket

Dana 300 Gasket


Senior Jeeper
1981 cj5 304 v8, 300 Dana,model 30 Dana and model 20 AMC rear end
In am pulling my dana 300 out to do the clutch. It has low miles on it. The dana seems to operate fine covered in oil though. Do I do just a seal reseal kit on it and put it back in if I cannot see anything wrong. Or do you ripp it apart and go through it. Having not done a case before I would then have to go to a shop. Hate to pay for something I do not really need to do.
I would check gears condition while you have the cover off. If the gears look good and it drives fine as you say I would do just the seals and gasket and be done with it. Remember to replace the 2 small shift rail seals, you can removed them with a small flat head screwdriver just be careful you don’t nick the seal seat or rail.
I take it the rails are the linkage that goes into the transfer case from the shifter? If so yes the rails look like they could be a bad area for leaks. Learning as I go I find it good thearpy.I will post pics when I get it out thanks.
Although this is a 20 housing you can see where I installed the 2 smaller seals using a socket.



This is my 300 before a 4.1 install

Got the tranny out can you tell me if it is a t176 by looking at the pick. the tranny has a bit of play on the shaft is this normal?
Clean the tag up driver, it could be a T176 or T177, the T177 has a lower first and second gear which is better for off road, both are good medium duty transmissions though.

A little play is fine, you can pull cover to get a look if you had concerns, since you have it out.
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The CJs only came from the factory with the T-176. The T-177 came in the trucks.

The casting numbers on the cover in your pic (C-2604208) tells me its an original T-176.
Good eye posi on the numbers thanks!
Posi - Cj's did come from the factory with T-177.

They are listed in the parts manual for CJ's. The truck T17x's had a considerably longer input shaft on them, so it is not a direct swap that people are likely to do for a realistically minimal first gear change.

I have 3 :eek: and all came from CJ's. In fact, most late model CJ owners who check the numbers on what they think is a T176 find that they are in fact a T177.

5359389=T-177 3.82 first gear
5359890=T-176 3.52 first gear

It really only makes a difference if you are replacing second or third gears or the cluster gear or input shaft. All the rebuild parts are the same, rebuild procedures are the same.

I’ve never saw a T-177 case in a CJ not saying it can’t be, and I’m not doubting you, just don’t understand the reasoning. The T-177 case was designed to mate with a 208 t-case so if used in a CJ the 300 wouldn’t be clocked correctly.

Is it possible what you had was a T-176 case and input shaft with the guts and top cover of a T-177? I’ve seen some unexplained things come out of the Jeep factory
Posi, it was factory, not modded.

You are forgetting the reason I had to buy my SECOND T177. The factory adapter. I was a little on the ignorant side then and bought the trans without it, hence the second purchase. The seller didn't want to split the package and sell only the adapter.

If you look at the parts list you will see the factory adapter. The T17x series was most likely developed for multiple vehicles. Just like the SR4,T4 and T5 used in CJ's from 81 on and AMC cars.

On the SR4, T5 and T4, the "second" half of the trans is primarily an adapter to what ever tcase (or 2wd vehicle) they were to be mated with. Automatics (again, used in multiple applications had an adapter for a t case or a tail for a 2wd.

On the SR4 and T4 the adapter is pretty much an empty case with the shifter on top. In the T5 it houses (covers) 5th gear and again the shifter.

The T17x Jeep series also didn't have an oil seal for the output shaft and bearing. The adapter has the seals. Same with the SR4,T4 and T5 IIRC.

If you look at the end of the T17x and the D300 adapter, they are not mirror images.

The adapter was probably used for multiple transmissions just like the trans was used in different applications.

And don't forget, Tremec ( the T in T17x, T4, T5) makes transmissions, AMC bought them, and installed in what they wanted. Who knows what other vehicles they may be in.

At any rate, I use the parts manual as a guide and then work that in with what I actually see.

Here's what the parts manual has listed for applications, and the blow up of the T17x and the adapter.


Posi - Cj's did come from the factory with T-177.

5359389=T-177 3.82 first gear
5359890=T-176 3.52 first gear

Yep, that was why I asked for the tag to be cleaned. It should list one of these numbers. Top cover's were most likely interchangable, t18's used t98 covers in the early years so it's possible those numbers won't tell everything.

*edit, although I will not pretend to be a pro on this tranny, I had researched as well. There are some other threads out there referencing long and short shaft (CJ5's and 7's)T177's so it may have been as an option or leftovers like the Dana 44 in 86 CJ's? Just a guess.
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I cleaned the tag hope it is readable. Pulled the oil pan off started on the main seals. One part just seems to connect to another. Well I am down there might as well do the seals.
Sorry for the bad pic the tag reads 5359389 1649 rgk Appears to be a t177 . Are they as bad as they are made out to be?
They are considered the more desirable option by most. 1st and 2nd (very minimal) are geared lower and give you a better crawl ratio off road. Not a huge difference, but better. 1st is 3.82 vs 3.52 on a T176.

If you have 2.73 rear end and Dana 300 is 2.62 low. Then multiply x your tranny to get final crawl ratio.

2.73 x 2.62 x 3.52=25.177

2.73 x 2.62 x 3.82=27.23

Off road, good final ratio is about 75 manual trans and 50 auto. It keeps your foot off the clutch and less wheel hop that tears out u joints, twists drive shafts and breaks axles.

Although lower torque also means more ft lbs of pressure on parts but IMO well worth it. You don't have to work hard to get through obstacles and thats what usually breaks things. Although , then you will take it the next level as you can do more crazy stuff, so you still break stuff :D
I have a new twist I showed the the pilot bushing to the boys at work and they were afraid that the bushing was so beat up they sent me home with a dial on a mag base to check the crank for movement. They also want to take a peek at the tranny to see if the input shaft is done for. I have never seen a bushing so beat up. I dumped the 2.72 gears and I am putting in 3.73
The fruit of labour a cleaner tranny.Thought the writing on the tranny still intact was cool.
Tooth brush and elbow grease WD40. Funny thing I thought it was smokn clean tell YellowCJ85 showed me a pic of his cleaned up. Hopefully he will post a picture of it here.I keep my hunting dogs in the shop over night so I do not do solvent tanks because of the smells. I prefer they use their nose on birds. I know I would hate to sleep beside a tank of varsol .Maybe at work I will hit the tank and get it better.
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Well was trying to show Driver007 something to look for on the out put shaft. If the output shaft splines look like this, might be time to replace the mainshaft. They have been worn down to a point almost.

They should look a lot closer to these. This was the new mainshaft.

Don't clean aluminum with a solvent cleaner, it turns it gray and is hard to shine up. Something like Purple Power or just soap and water and a hard scrub brush. Then a coarse wire wheel on a bench grinder, then a fine one. The case was empty so it's pretty easy to handle on the wire wheel. Takes about 20 minutes. Wouldn't even attempt a full trans.

You can see the shine a little better here.

Driver, here is the reverse idler gear (lower right). It tends to move easily, so make sure you get the fork on it first when the shifter goes back on or you'll be pulling the trans again.:D


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