Newbie looking for suggestions on Drivetrain

[Murkure]

Hello all. I am brand new to the site and essentially brand new the jeeps, again. Acquired 1978 Jeep CJ7 . Sat with a seized engine for over 10 years in my fathers backyard. Shipped it to CO last year and have been throwing money at it since. I replaced the engine, AMC 304 V8 to a 360 V8, replaced wiring harness and now looking to start working on the drivetrain.

I took it to a local shop and was given suggestions. First off, I am not familiar with Jeeps and I have a lot to learn. This was my first car and I am rebuilding to be a driver again. 85% on road and 15% off road. This jeep has been tinkered with for 10 years by my father, uncle and brother. So, there is a mix and match everywhere on this jeep, except for the tub, which is in good shape.

Local shop stated to replace Transfer Case and Rear Axle. Suggestions are Dana 300 T-Case and Dana 35 Rear Axle.

I plan on placing a 4 inch lift, installing 33 inch tires and I am looking for suggestions on T-Case, Axles suggestions and Gear Ratios based on 85% road/15% off road.

Will get pics up soon. Thank you for your suggestions.

 

[Old Dog]

The Dana 300 Transfer Case is good (nothing wrong with the Dana 20 in it now though) but do NOT use a dana 35 rear, they are very weak. The AMC20 (if you add one piece axles) in it now is much better.
For 33" tires I would go with 3:73 or 4:10 gears.

 

[Manhattan]

Old Dog is 100% correct. The local shop is confusing CJs and YJs (Dana 35 is a Wrangler axle). I'd be a bit concerned about that shop. That Dana 35 would be an expensive hassle to install - you'd even have to buy new wheels!

But back up a bit - Why did he say to replace the Transfer Case and axle? Unless they're cracked/bent, etc. I'd keep 'em. I could see rebuilding them - if that's what they need. If you're rebuilding the axle, swap in a set of one-piece axles, while you're at it. The stock 2-piece axles are kinda week.

But assuming the shop has reason to replace, I'd stick with a Dana 20 t-case or a Dana 300 - both are very stout cases and direct bolt-ins (assuming they came out of CJs). For axles - again, assuming the axle has to go - I'd stay with the Corporate 20 or a Dana 44 out of a 1986 CJ. These are the only direct bolt-ins.

This could be an opportune time to upgrade BOTH front and rear axles. In 1982 Jeep widened the CJ axles by 4.5" a.k.a. "Wide Tracks". Some '82 and all '83s and up have the same 20 (rear) 30 (front) combo - they're just wider. This is a common swap, because the spring perches (mounts) are identical to the older CJs. The wider axles bolt right in and make the Jeep more stable - on and off road. You'd also need to swap in the front shock mounts and the brake lines. But that's cheap and easy.

CJ axles - pre and post 1982 are VERY cheap. In fact, I gave a set of wide tracks away last year... after trying to sell them for $AMC 150 .

 

[Saddle Tramp]

Welcome to the Wonderful World of Jeeps! You will quickly lean that this is an addiction that can’t be cured with a 12 step program but can be medicated with the acquisition of jeep parts; I would guess by now you already know that.

The 1976 to 1986 CJs have a few advantages when it comes to upgrades as some of what you need is either already on your jeep or available on ebay, Craig’s List, or the bone yard. You state that it is your intention to make this rig a DD with limited off road. That tells me you want to keep the gearing in the differentials fairly tall (numerically lower) to keep the motor RPMs down when on the road however it is a great thing to be able to lower the gearing down when off road even if it to just drive down a dirt road at a leisurely pace. Jeep used a T18 transmission in CJs starting in 1972 through 1979. It came in two versions; with a 4.02 low (1st) from 1972 to sometime in 1976 (records of when the switch was made are unclear) then changed to a 6.32 low (1st) sometime in 1976 to 1979. The latter 6.32 low is the most coveted due to its lower gear. The bell housings used in 1977, 1978, & 1979 are drilled for both the CJ version of the T18 and what is called a Ford “butterfly” pattern to fit the T150 (same as the Ford T18) standard transmission of the day. This gives you the opportunity to use either a CJ or a Ford T18 transmission with minimal fuss. Check this out:

http://www.jeeptech.com/convtrans/cjt18/

http://www.jeeptech.com/convtrans/fordt18/index.html

As far as the transfer case you should have a Dana 20 which has a crappy 2.03 low gear ratio and yes the Dana 300 is a much better choice at 2.62 low from that stand point. Both are good strong cases however. If you select a CJ T18 the back of the T18 has a 1” adaptor that in reality is part of the transmission that allows the Dana 20 transfer case to be bolted to the transmission. The bolt pattern is known as the “Texas” pattern as the layout resembles the corners of the State of Texas. Should select the Ford T18 you need a shaft kit and adaptor to bolt up either a Dana 20 (Texas bolt pattern) or Dana 300 (round bolt pattern) to the transmission and should you want to use a Dana 300 may be the best way to go. As you have a CJ7 and not a CJ5 you do have enough room to add the round adaptor behind the transmission for a Dana 300 without making the rear drive line too short but not by much particularly if you plan a 4” lift.

Both the Dana 20 and the Dana 300 have aftermarket kits available to lower the low range gearing. Dana 20 = 3.15, Dana 300 = 4.0. This is important as a daily driver as if you get the gearing in the axles too low as I said above will not be a good thing. To do a transfer case gear reduction will allow you to keep your “street” gearing for the road while having a decent “crawl” ratio when not.

 

[JR74CJ5]

A lot of what I would mention has been, but please bare with the repetition...

1. You state On/off 85%/15% - I believe above is correct: Think about a T-18 and Dana 300 Combo. You can keep the Axel ratio high enough for comfort on the road, and only use granny / low tcase off road.
2. No on D35. Dana 44 or Corp 20 1 piece conversion.
3. 4" lift: What for? Looks? someone told you for 33's? etc. Not knocking your choice, just making sure you are fully informed. A 4" lift will be a LARGE project. For a 7 it;s not AS bad, since you have a few extra " in the rear, but your drive line angles, drive lines themselves, steering geometry, brake lines... all need to be addressed. Again, not to scare you off what you want to do, just be ready. It is my opinion 4" is too high for a 85% / 15% on/off rig with 33's. Nor reason except looks, I can't argue the looks
4. What is the purpose of the drivetrain swap? are things broke? in need of re-build? what do you have all around?

~ JR

 

[Murkure]

Thank you all for the replies and feedback. I really do appreciate it.

1. I am unsure which Auto Transmission is currently in Jeep. I will be taking/posting photos for everyone to view.

2. 85%/15% is my desired current setting as I have no need to purchase another vehicle at this time. When I move or get a new job (currently work across street), I will be turning this vehicle to a 80%/20% Off road/road vehicle. I told the tech that I will not be rock crawling, but want to drive around the ranch at a decent speed. And if I come across a tree, rock or whatever, I do not want to break anything while traveling 30ish (If I do not see it before it is too late). Of course, I reserve the right to change my mind in the future.

3. 4 inch lift with 33's for the looks and future playing around in the wilderness. I will ask my lift questions in the appropriate forum when I am ready to start thinking about that.

4. I think I am going to replace the front axle as well.

With my above desires, the 4wd.com store techs gave me the suggestions regarding the Dana 300 Transfer Case and the Dana 35. But I was unsure about the Dana 35 after reading about it.

I "plan" on having this Jeep until my they ban the use of gasoline vehicles and then I will convert to some other fuel source. So, I want to do it right the first time. And this vehicle was neglected for far to long.

Thanks for the suggestions and keep them coming. I hope to benefit from your experience.

 

[3QuarterTon CJ]

I'm guessing you have the Quadra-Trac Transfer Case , with the offset model 20 rear, which is why they suggested changing them out.

Do you want to keep it automatic, or are you adventurous enough for the 3rd pedal? If you keep the slushbox Transmission , just get the adapter for a Dana 300 t-case, and get a centered model 20 rear with a 1 piece axle kit. That axle whether it be narrow or wide track will be plenty strong enough to handle 33" tires and 15% wheeling.

I would suggest getting wide track axles front and rear. But I'd keep the 6 bolt lock out hubs that you should have on the front now, just swap them over to the wide track front axle. Also I'd say 3.73 gears should do ya good, however since you say you work across the street, I'd probably opt for the 4.10's for better crawling around, better control off-road.

 

[Saddle Tramp]

You have some big decision to make and they all involve money.

Murkure-

I would think hard about the 4” lift for running around the ranch. Having owned a CJ for much of my adult life in my opinion about 2-1/2” of lift is best and that is with springs not a shackle lift. Maybe pick up another 1/2” – ¾” with your shackles but that’s it. CJs are a little tippy by nature and raising the weight too high in the air is not a good thing. ThreeQuarterTon suggestion of swapping out your stock axles to wide track axles is not without merit as far as helping stability but may not be necessary for your intended purposes.

But before you can move forward it would be best to decide which transmission and transfer case you plan to use. The existing (assuming) Quadra Trac and the possible swap Spicer 18 are both offset rear drive while the other options, Dana 20 and Dana 300, are both centered rear drive. Once that decision is made it will dictate what axle choices you have.