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AX15 w/ Hydraulic Clutch... Possible?

Goody

New Member
Joined
Sep 12, 2018
Messages
30
Loc.
Pensacola, FL.
So I’m wrapping up my motor rebuild and staring at a nasty rat/ran 3 speed and Dana 20 sitting in a concrete tub on my garage floor. Doing my normal web viewing of EB stuff, I come across a kit on WH for a AX15 w/ clutch(which I need anyway) w/ Dana 20 adapter and all the goodies. My clutch linkage assembly is mostly garbage from my inspection after motor was removed, clutch fork adjustment rod is all jacked to the max(probably from burnt out clutch... but whatever). Is there anybody w/ experience w/ converting this trans input shaft to a hyd. setup? I am looking for a complete conversion to not have a clutch fork anymore, unless it’s out of bounds thinking that way, and could fall back to having the slave cylinder(?) mount to the bell housing perimeter bolts that pushes the fork to engage the throw out/pilot bearing. Something similar to this Summit setup below:
https://www.summitracing.com/parts/...MI-NrBkdeM3gIVRFuGCh3jAAZvEAQYGSABEgLnvfD_BwE

Also, is there a way to determine if flywheel is trash? Do they wear out, per say? I’ve cleaned mine up in the parts washer but would hate for a $150 part to be the issue after everything buttoned up!

And last, I intend to convert to a 4bt cummins, later on, and if there is a better option that’s not NV4500 price for trans kit... that may force my hand to not have to buy stuff twice. Torque ratings are an issue b/t a v8 and diesel from what I’m seeing on ratings.
 
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bronconut73

Bronco Guru
Joined
Aug 7, 2012
Messages
9,916
Yes on hydraulic.
Guys here have done it.
I have seen their little slave cylinders ....

The 4BT torque "could" destroy the AX-15 or NV3550.
I guess if you were real careful but that ain't no fun, lol,
 

SDBMtber

Jr. Member
Joined
May 20, 2018
Messages
130
Not a guru or even experienced on this, but my plan is to go hydraulic clutch with AX15. There are some threads about doing it with the normal bronco bell housing, with various transmissions. The setup I plan to go with used he late 80s early 90s ford truck bell housing. These came with a hydraulic clutch which you can get the master and slave with hose pretty cheap. Not sure if this will fit exactly as-is or I’ll have to do a different master or something. That’s about all I know so far!

Here’s a pic of the bell housing and throwout lever where the hydraulic slave mounts.
 

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Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,821
The 4BT isn't a smooth engine. While the stock torque is respectable, that is average torque. the power pulses are a hammer. While it may be possible to bolt all the parts together, and on paper the torque is inside the ratings, it will still kill the transmission in short order.

GM did this in the early 80s. Half ton trucks with a 5.7 diesel and a 3-speed manual transmission. the warranty repair for the destroyed 3-speed was to put a big truck 4-speed in it with a block off plate over the granny gear. You still had the 3-speed. But it was a stout enough 3-speed to take the pounding of a lame diesel. The 4BT makes more power on fewer cylinders, it hammers harder on each firing cycle. Use a real transmission behind it. The 6BT NV4500 will bolt right to the 4BT. No high dollar aftermarket adaptors needed (transfer case will take an adaptor no matter what).
 

sykanr0ng

Bronco Guru
Joined
Aug 11, 2014
Messages
5,363
The 4BT is four cylinders each about the size of a gallon jug going BANG_BANG_BANG_BANG....
The difference between a V8 gas engine and the 4BT is like the difference between a breaker bar and an impact wrench.

The AX15 is prized for its car-like shifting not brute strength.
A brute strength engine should be backed by a brute strength transmission.
 
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Goody

Goody

New Member
Joined
Sep 12, 2018
Messages
30
Loc.
Pensacola, FL.
Would never think of intend of putting any of these typical bronco transmissions behind a 4bt. Was just wondering if anybody had a option for a trans that I could mount behind the v8 and 4bt, to keep me from potentially having to buy 2 transmissions. Am not against a auto but it just seems highly unlikely a TH400 or a heavier 47/48RE in that tunnel!! Haha
 

sykanr0ng

Bronco Guru
Joined
Aug 11, 2014
Messages
5,363
Would never think of intend of putting any of these typical bronco transmissions behind a 4bt. Was just wondering if anybody had a option for a trans that I could mount behind the v8 and 4bt, to keep me from potentially having to buy 2 transmissions. Am not against a auto but it just seems highly unlikely a TH400 or a heavier 47/48RE in that tunnel!! Haha

Both the NV4500 and the ZF S5-47 will stand up to a 4BT.
Why they are not the usual choice among the street Bronco crowd is they do shift like a heavy duty pickup truck transmission because that is what they are.
For your use the NV4500 is probably the better option; as Broncobowsher says it will not need an adapter on the engine side.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,821
Well what transmission do you want? You start off with a stick shift and now you are discussing automatic options.

Diesel gearing needs are different from that of a gas engine. You typically find diesels with higher final drive ratios and closer ratio manual transmissions. It just is a better match for the torque curve of a diesel.

Automatics are a bit of an oddity. for the most part they are designed for a gas engine and adapted to a diesel. The gearings isn't a match, but the convertor is enough of a crutch that they work.

Getting one transmission to work with both isn't going to work. If you drop the 4BT down to an ISB2.8 those do work with the AX15s, and the adaptors do exist in the aftermarket. It isn't the brutal hammer of torque of the 4BT. It has more RPM to it, so it behaves much more like a gas engine. A modern diesel.
 

Dbteak

Sr. Member
Joined
May 23, 2006
Messages
438
I think the NV3550 or the new AX15 can hold up fine behind the 4bt. I have almost 50,000 miles on my 4bt/NV3550 set up. It's my daily driver and take it to Moab and Rubicon. I have not had any issues with the transmission. I also did a hydraulic clutch converstion.

http://classicbroncos.com/forums/showthread.php?t=252720
 

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Goody

Goody

New Member
Joined
Sep 12, 2018
Messages
30
Loc.
Pensacola, FL.
Well what transmission do you want? You start off with a stick shift and now you are discussing automatic options.

Diesel gearing needs are different from that of a gas engine. You typically find diesels with higher final drive ratios and closer ratio manual transmissions. It just is a better match for the torque curve of a diesel.

Automatics are a bit of an oddity. for the most part they are designed for a gas engine and adapted to a diesel. The gearings isn't a match, but the convertor is enough of a crutch that they work.

Getting one transmission to work with both isn't going to work. If you drop the 4BT down to an ISB2.8 those do work with the AX15s, and the adaptors do exist in the aftermarket. It isn't the brutal hammer of torque of the 4BT. It has more RPM to it, so it behaves much more like a gas engine. A modern diesel.

I am not hung up on manual or auto... guess I should have spelled that out better. Just if there is an option to cover both setups and not have to buy another trans when I convert.
 

Mike Bernard

Newbie
Joined
Dec 4, 2015
Messages
30
I have an AX15 with an tilton internal hyd throw out bearing in mine for the last year no issues. I have not had any issues so far with the AX15 behind my 351w with around 450 torque.
 

pblackb592

Jr. Member
Joined
Apr 25, 2007
Messages
83
The 4BT is four cylinders each about the size of a gallon jug going BANG_BANG_BANG_BANG....
The difference between a V8 gas engine and the 4BT is like the difference between a breaker bar and an impact wrench.

The AX15 is prized for its car-like shifting not brute strength.
A brute strength engine should be backed by a brute strength transmission.
I just read this and looked up the bore on a 4bt. It's 4.020 so it's .020 over a 302. Not a gallon jug. SMH.
 
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