400 Turbo Trans/Dana 20 T-Case Shifting Problems

I am the proud new owner of a 74 CJ5. My first Jeep.

She has a Chevy 350 small block, 400 turbo trans adapted to a data 20 transfer case with Dana 30 front (3.73 open) and Dana 44 rear (3.73). It has a mini spool, which I'm going to have swapped out, probably for a Spartan locker.

I bought it a few weeks ago and have been doing various things, like spark plugs, installing a new Mojave heater (keeps things toasty) and putting on a top and doors (fiberglass body, so I had to do so mod work to make everything come together).

In any case, this weekend is the first weekend I've had a chance to get it out on the road. With the automatic transmission in "D" and the t-case in 2 HIGH, the tranny won't shift into 4th gear (or so). She gets up to about 25 MPH, then I can hear things whining from underneath. Rather than push it and risk breaking something, I've just backed off the throttle and slowed back down to 25 or so.

I'm not much of a gear head. Don't know if it's the tranny, the t-case (or both) or something else that is going wrong. The RPM's stay at about 1,000, even as the whining occurs, which makes me think it isn't the transmission causing the issue directly.

One more thing... Just to be certain that I wasn't in 4 LOW, I shifted the t-case to neutral and then went back through the gears to make sure I was right (since it isn't marked). When I shifted the t-case from neutral back to 2 HIGH, there was a lot of grinding. I pushed it through and into 2H just fine, but wasn't sure if it was supposed to grind like that - I'm guessing not.

Any suggestions?

 

A th400 is a 3 speed. non lock up.

and shifting a d20 should be done while stopped.

 

Well that explains why it won't shift to 4th!! I'm going to take it back out and see if I can better identify what is whining at that speed - maybe it's just the tires?!?

I did shift the D20 while the vehicle was stopped, but in Drive. That's where I heard the grinding. The t-case won't shift when the trans is in park, that's why I did it in drive.

 

The whining you hear could be driveline vibrations, since I assume your rear driveshaft is extremely short and at a steep angle of operation (the automatic is VERY long, and was never used by the factory for that reason). As stated above, the TH400 is a 3-speed, so it will only shift twice.

 

shift with the trans in neutral. and maybe at a 1-2 mph rolling speed, max.

 

You're sure it's a TH400 and not a TH350? A TH400 is pretty long for a CJ-5, and would make your rear driveshaft very short. The TH350 is a more common choice.

If you don't get on the throttle a lot, your transmission will shift into top gear at about 20 mph and go up to highway speed. Realize that a Jeep makes a lot more noise than a passenger car does. Noise comes through the uninsulated steel floors, you have more gears turning, and the tires make a lot of noise. And the low gearing makes engine speeds seem high on the highway, compared to passenger cars. it's just what you get with a Jeep.

Which shifter do you have? The original transfer case U-shifter used with the Dana 20 and TH400 can be very tough to get into gear. Plus they are often worn out...

You should be able to shift from 4WD high to 2WD high at any speed, as long as the front hubs are locked in. Don't try it with the hubs unlocked. You understand about high range and low range?

The shift into or out of low range is not meant to be done with the gears moving. But sometimes you have to bump the gears a little to get them to line up and go in.

Low range should be shifted when fully stopped. If you can't make it shift in Park, shift into drive, move ahead a hair, shift back into park, and try again. Your last resort is to try what Dante suggests - move in drive with foot on the brake at an absolute baby crawl, then shift into neutral and try to shift.

 

Thanks for all the replies. I think I was just paranoid about breaking something. I was driving around the neighborhood and could hear a lot of noise and backed off... I took it out on the highway and was able to get up to speed without issue and drove it 20 miles to work this morning at 40-50 MPH. The T-case does grind when I shift, even when completely stopped. I'll verify TH400 or TH350 and the shifter tonight.

 

CJ7 came stock with a turbo 400 and a 13" driveline.
Best to shift the transfer case with the trans in park. With the trans in neutral it will still allow the spinning of the transmission enough to cause grinding. Check the 4 1/4" bolts that hold the shifter into the housing. Often these bolts come loose and allow slop in the shifter allowing even more wear. The "j" type shifters are often misunderstood and not serviced so they are not liked by many.

 

yes it came with it....but cj7 were made for automatic trans with their 12 inch longer wheelbase. Also he doesn't have a amc v8 but a SBS 350, heard some did it but i would pretend that he have a th350 and a dana 20. Already seem people with this set-up having a short driveshaft so a th400 i'm realy not sure...
m2c