Exhaust and tire size for my BJ42

[Mike G.]

I need to replace my exhaust system and was wondering if there is any advantage to going to a larger size pipe to help the engine breath better. My thinking is since larger pipes help the Ford, Dodge pickups, maybe it would help my Cruiser.
I am also thinking of some new tires and was wondering if 35x11.5 MTR's are too big for the 3B engine. I have a 4" lift, so clearance is not an issue.
Thanks for your advice!

 

[dieseldog]

Given stock ring gearing, the 35's are probably too tall for your 3B. I run 33's on my 3B-equipped cruisers and I feel it's just about right. If you turbocharge, change out your ring gear, and add a lift of at least 2 inches, you can probably run the 35's. Do you have the 4-speed or the 5-speed?

 

[Mike G.]

I've got the four speed with the split case transfer. I was wondering about upgrading to the 5-speed. I have one in my 60 and love it. Is the install into the BJ a simple swap, or is more involved?
Also, what ring gear size would you recommend if I went with 35's?

 

[crushers]

with the H55F instlled you will be able to turn the 35s easier but 5th gear is useless. i ran a BJ42 for years with 35s, it is a slow rig but rocks off road. add a turbo and the whole truck transforms into a much mor epleasent driving experience.

the H55F is a bolt up but you need to modify the driveshafts the front is 3" longer (i beleive, measure beor you modify) and the rear ends u being a 2" pipe when using a CV joint driveshaft (which i recommend) from a 60 series.
you will need to cut the shifter hole back 3" so the tower will fit through.
if you use the 4 speed gears make sure you get the 5 speed t;case and just swap most of the guts over. you need the 5th gear oiler that is in the 5 spd case...
cheers

 

[Diescipel]

There isn't a difference in the frames in the 83-84 BJ42s with the H55F? I thought the curly-tube cross member on the frame was moved back slightly to accomodate the longer 5 speed tranny?

I'm sure I'm wrong--just thought I heard this somewhere, sometime.

I will 2nd what folks are saying on tire size--I have 33x9.5s on mine and it seems just right though w/o turbo I am frequently downshifting into 4th on hills. It may be that 33s are a bit big for the higher 1st ratio in the H42? They are perfect down low in the gearing on the H55F.

B

 

[crushers]

i do beleive you are right. the conversion leaves about 1" between the back of the t/case and the cross member.
you need to stick the tranny and t/case on the engine then lift it up to put the mount in place...

 

[Diescipel]

Ok so you don't have to move the X member? Roger.

B

 

[Greg_B]

Correct.

However, I know some people have cut the tube right at the frame, attached a plate to each side, and now bolt it in and out, when they have to do work to the tranny.

I ran 255/85/R16's (33x10) for years on my H42 BJ42. Starting on a steep grade in 1st H can be a pain. For regular driving around (city and highway), it seems right. I can see 1st with an H42 being a real PITA with 35's.

gb

 

[crushers]

yes, i have seen this done but for the home do-it-yourselfer, a straight bolt up can be done...

 

[Tapage]

Correct.

However, I know some people have cut the tube right at the frame, attached a plate to each side, and now bolt it in and out, when they have to do work to the tranny.

I ran 255/85/R16's (33x10) for years on my H42 BJ42. Starting on a steep grade in 1st H can be a pain. For regular driving around (city and highway), it seems right. I can see 1st with an H42 being a real PITA with 35's.

gb

but 4.11 R&P .. ?

 

[Greg_B]

but 4.11 R&P .. ?

Yes, sorry. Stock 4:11 in the BJ42.

gb

 

[Mike G.]

OK, sounds like I should stick with 33's for now. The 5 speed man come sometime in the future. Any thoughts about increasing the exhaust pipe size?

 

[Diescipel]

LOL here we are talking about tranny swaps and you want to know about exhaust size...

I assume you are into your BJ42 for the long haul like me, and I assume you have not turbo'd it. I'm interested in a turbo in the (distant) future, so if I were you I would build your new exhaust for that possibility. Larger exhaust won't help you much now without turbo, but it will in the future with it, if you are considering it. With this in mind, I would go with a 2.5 inch galvy exhaust system and a very free flowing muffler (which you can remove easily when the turbo comes). That's what I would do.

My .02

B

 

[BJ40 3B]

4.56 would be enough?

Should a turbo'ed 3B @ 0,8bar, intercooled with stock 4speed gearbox and 4.56 R&P would be enough for pushing 35's, or should i go with higher R&P ratio? for now i have the stock 4.11 with the 35's but it seems it's not a good option.

 

[Greg_B]

LOL here we are talking about tranny swaps and you want to know about exhaust size...B

lol...yes: The main question. I did exactly as you mentioned, and built my exhaust for the future possibility of a turbbo. 2.5" with a free flowing muffler. I needed a new exhaust anyway.

Yes, I believe there is an advantage even without a turbo. The better you can exhaust the hot gases...well, the better! Are you going to be making full use of it? Probably not till you have a turbo, but if you have to do the exhaust anyway...do it.

gb

 

[crushers]

Should a turbo'ed 3B @ 0,8bar, intercooled with stock 4speed gearbox and 4.56 R&P would be enough for pushing 35's, or should i go with higher R&P ratio? for now i have the stock 4.11 with the 35's but it seems it's not a good option.

yep, that should turn 35s quite nicely...
cheers

 

[Tapage]

For a good fuel economy 4.11 for good power 4.56 ( not much top speed )

 

[blownbj]

You'll get your speed once you take the overall tire diameter into consideration in the final output ratio of your driveline, but will you have the power to get the tach up. Start saving for the AXT now and you won't regret it.

 

[crushers]

AXT makes a s***ty kit for the 2H, for that kind of money you would think they could design a clean install...

 

[Tapage]

AXT makes a s***ty kit for the 2H, for that kind of money you would think they could design a clean install...

Well I never seen the AXT 2H turbo Kit .. but anycase the second part of the sentence is right .. 3000 USD not a joke ..