[27TRoadsterguy]

My 1975 Chev inline 6 was equipped with a Muncie 4 speed. I would like to use a 4 speed automatic in my new project car. If I find a flex plate that fits the crankshaft, can the th400 or L60E be bolted up to my 292 cid engine. Since my goal for this engine is 400 to 450HP I should probably be using a 4L85-E. Anyone with the info I need? Thanks.

[poncho62]

My understanding is that any Chevy trans should bolt right up....6 or V8

[Crosley]

4L85e trans is too much for the inline 6, I would suggest a 700r4 - 4L60 series trans mission if an over drive trans is needed

[27TRoadsterguy]

OK, that's what I thought it should bolt right up. Yes an OD transmission is a good choice with the torque available. My engine guy says the torque of the 6 will be close to 500 ft lbs with the boost and injection system, to take advantage of that the OD will give me a good top end, while taking advantage of a tire burning rear end ratio. I could do up an 700R4 that will handle the torque the 6 will deliver, but there is no cost difference between that and a 4L80E with the same power and torque handling capability. The 4L80E will give me full manual control that the R4 won't.(something I want). The R4 is somewhat smaller and lighter, that I will give you. I will make the decision in a bit, I have a while before I need to make that choice.

Thanks guys

[AutoGear]

4L80 is a BIG trans; We aren't concerned with you finding a trans to take the abuse; its more of the packaging and the amount of parasitic loss involved.

One of my customers builds 4L60E's and electronic control with cars in the 10's. PM me and I'll get you some information. They also do 4L80s, 700r's and the occasional very bad *** T56.

Note: you probably should have mentioned the ECM, Boost etc etc on your inliner and that you were going with a high-tech theme to the build.
a 'normal' 400hp I-6 builder probably has carbs and would feel more comfortable with the 700r or the 200-4r. Additionally I say keep 4 speed sticks alive but; I understand your thinking

[27TRoadsterguy]

Yes I do understand the issues with the 4L80E I have one in my trans am.It is a huge tranny, and yes the parasitic losses are huge. I am shooting for 500 hp and 500 ft/lb of torque in my ultimate goal. I love the SM465 muncie, it would probably handle all I can give it, but the ratios don't work, To get a decent top end speed I will need to go to a numerically low rear end. An OD unit solves the problems and gives me a good off the line and a decent top end speed. I know there are OD units around but they are pricey....I will make the decision when I get to that point

Thanks guys