Looking for tranny sugestions

I have a friend who wants me to help him figure out what to do with his '73 CJ5

To start with he has a 304 and stock 3 speed.
As well as a stock d 20 Tcase.
It has built 60 axles with 5.38's , 36 inch Super swampers,that have to stay.

What he want's is lower crawl range and lower highway rpm...

Note; dont we all..

My first thought was a t18 which whould solve the crawling but do nothing for the highway.

I talked to Herm and he suggested his ford RTS overdrive tranny.
But that dosent do much for crawl ratio.
So then maybe add a terra low kit to the tcase???


What would you do???

 

Adjust the gears in the axles for the highway rpms. 4.88s or 4.56s would be great. I ran 35's on 4.56's. They wold get the RPMS down below 3K on the highway.

Then put in a granny low tranny and terra-low the t-case.

with 4.56 gears, t-18 wide ratio and terra-low 20, you would be looking at a crawl of around 91 to 1.

 

If money is no object/perfect word: GM 4.3, NV4500 granny 5 speed, D300 or atlas @ 4:1

In reality you already know there aren't many options, especially if your buddy wants to keep the 304. Swapping in a 4.3 opens up the possibilities if it is pushed all the way forward. I have a buddy who went that route and used a NV3550 5speed with and atlas 4:1 with 4.27's. It really was the best of both worlds.

Other options could include offsetting the rear axle and going with a D18 with an overdrive behind a T18.

Your overdrive 4speed with terra lows might work but you have to do the math on the crawl ratios and see if it would be comparable to one of the granny 4speeds.

 

With the stock trans, t-case and those gears the crawl right now is around 32 to 1.

The only way to get better highway RPM is to either do an over-drive tranny or regear the axles. The cheaper method would be to regear the axles. Then look at alternatives to fix the low range.

Terralow gears will give you a 3.14 to 1 reduction instead of 2 to 1. Keeping the same gears and transmission that will give you a crawl of around 50 to 1 which is about the same as a stock TJ rubicon but does nothing for your highway RPMS.

If you regear the axles to 4.56 and do the terralow then your crawl would be about 43 to 1. This would give you a 30% better low range and still improve your on-highway RPMS.

4.88s would get you 46 to 1 low range.

Now say you throw in a t-18. Your first gear goes from 3 to 6.32 to 1. you still maintain the highway performance improvement but your low range becomes 90.49 with 4.56 gears and 96.8 with 4.88 Gears.

This is why I was recommending the 4.56 gears. The 4.88s don't give you enough improvement in low range to compensate for the increased highway rpms.

 

I agree and that's probably what I would do. Just trying to give some out of the box ideas, since in general there seems to be an affinity for 5.38's in the rock crawling world. Great if you have a dedicated trail rig, but in my opinion the gains off road do not out weigh the negatives on the street.

 

I have been working the novak calculator also.

seems like a t18 and 4.56's would fix it.

We dont really rock crawl much,
this would give a Crawl of say 60 and around 2500 rpm on the hyway..... give or take with 4.56 to 4.88's

That seems reasonable
He is wanting a locker so axle would be open anyway....

 

I have a different view of the world. I believe the gears should compensate for the tire size changes. Leave the gear reduction to other components up the drive train.

My 5 with the 258/t-18/terra low 20/4.56 gears on 35s hardly ever saw 1st gear low range. It was normally in 2nd or even 3rd in low range. But for those very rare occasions where it was used it was amazing.

 

I agree completely, I love my 3.73's and T-18. No Terra low's yet, but it's coming.

 

Interesting. I’ve never heard of the Ford RTS transmission before. This came from a Ford board so I don’t know how reliable it is but here it is anyway.

 

The NV4500 has a removable bell housing doesn’t it? At least I’m assuming it does since most GM standards do.
The NV4500 is a good transmission and would give your buddy what he wants, a granny low first and OD fifth, but it’s an expensive transmission even before your buddy starts buying adapters to bolt it up to what he’s got.

 

http://hermtheoverdriveguy.com/id41.htm

Look here I wounder who copied who LOL.



Whouldnt just going for the gear change to 4.88 and a T 18 be the economical route??

 

Sorry for double post ERRR

Heres the rts on Herms site.
I wounder who copied whom.
Scroll down when you get there.

http://hermtheoverdriveguy.com/id41.htm


Just changing axles to 4.88 and a T18 would be least complicated

 

Is this actually a driver? Most people worried about crawl ratios haven't actually driven the rig yet. A 225 with a t-18 and 456 gears is crazy low in first gear low range. Like one of the above posts stated, a rig with that low a ratio will almost never see 1st or even 2nd gear in low range. It also makes reverse in low range useless as it feels like it takes ten minutes to back up ten feet.

 

I guess it all depends on where you wheel right?
Were talking about a rig that has a 304, t15, Dana 20 Tcase and 5.38 with 36's
This gives him 60 mph at 3012.8 rpm and a crawl ratio of 32.
It is a pain to use.
I and one other friend have 225's with sm420's.
Which puts us respectivly in the 50 to 60's for crawl range

He would like something around that for a crawl range and keep it in the 2500 rpm range on the blacktop.

For where we wheel this is perfect.
It is a driver and he has driven ours as well.
His is the Yellow one.

 

I expect these transmissions are the same as the SROD (Single Rail OverDrive) type, which is essentially a 3-speed with overdrive. It's a variant of the Ford Top Loader transmission, and a side shifter - I don't think there's any way it would work as a top shifter. It works by putting the overdrive gear in the same location on the cluster as 3rd would be on a conventional 4-speed. Thus if you top shifted it, you'd have to go 1-2-4-3 instead of 1-2-3-4. You can find a lot of discussion if you Google for SROD transmission. Here's a good page: http://www.5speeds.com/toploader.html

 

Tim, they are different. The RTS is a top shifter transmission with a special linkage in the case similar to the SROD and T-5 that allows the standard 1-2-3-4 shift. They are a 3 speed where 4th is overdrive but 3rd is a slight underdrive, not 1-1. They were used in only a couple years of full size Bronco's/F-150's and are getting darn hard to find. Hard parts are almost non existent. While I like the idea of the set up (I was going to put on in one of my projects), I shied away because of how hard parts are getting to find for them, and I have "in's" at transmission supply houses.

I'd like to add that fitting an NV-4500 in a CJ-5 isn't going to happen without pushing the motor way forward and lengthening the wheel base. They are just too long to fit in a stock length CJ-5, especially with 36" tires and the accompanying lift needed. I know, I have on in the '6.

 

NV4500 is also LONG, expensive, and extremely picky about getting its expensive fluid. IMHO it got over hyped as the silver bullet for gearing.

 

X2! Nice to be able to hit the highway speeds and still crawl on the trail.

 

The RTS is about the same strength as a T-176 and is considered a medium duty transmission. It definitely is NOT a heavy duty transmission in the league of a T-18, SM-465, or NP-435. That's why many of the hard parts are getting so hard to find. It also will NOT bolt directly to a Jeep model 20. Possibly the 4x4 version could bolt to an Early Bronco 20 which is a completely different animal and the front output is on the driver's side. Again, 3rd gear is not 1:1, at least not the couple I've had in my posession fwiw.

 

I just run GL4 AMSOIL Synthetic gear lube in my K3500, almost 100k since rebuild. IMHO You do not need the fancy expensive dealer fluid.