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When it comes to installing an automatic transmission, it’s easy to get lulled into thinking: “This is a piece of cake – all I have to worry about is the trans and converter”. Not quite so fast. There are a lot of critical little pieces you should pay attention to, aside from the transmission and torque converter. Some of those little pieces include the flexplate, flexplate bolts (to the crank and to the converter), bellhousing bolts, cylinder block dowels, transmission mount (and crossmember), cooler, cooler lines, shift linkage and more. It gets complicated – especially if you don’t do something right.
Getting it right is the backbone of this series. The idea is to provide you with a number of automatic transmission installation tips and tricks (the majority of them courtesy of ATI Performance Products – https://www.atiracing.com). None of this is difficult, but you really can’t afford to skip any of the steps. Check it out (and stay tuned for Part II):
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When installing a converter, it's easy enough to get it wrong. Plenty of good mechanics miss it. I use this simple ATI shipping tool to ensure the converter and transmission input splines are correctly engaged. It saves a ton of heartache if you don't get it right. Once installed, ATI advises that the converter must be free to move at least 1/8-inch to no more than 3/16-inch in order to contact the flexplate. If the converter is “locked” or extremely close to the flexplate, remove the transmission and double check the converter installation on the transmission input splines. If there is more than 3/16-inch clearance, add shims between the flexplate mount pad and the converter.
This is the ATI SFI 29.1 spec flexplate I’m using in my application. It’s a 168 tooth example for use with an internally balanced, two-piece seal big block Chevy (small block is the same). The configuration is critical! You must always ensure you use the right flexplate combination – internal balance, external balance, seal configuration, ring gear tooth count. Get the right flexplate. You can’t mix and match.
To mount the flex plate on the engine, you have to make sure it's oriented correctly (don't laugh -- some get it backwards). It’s difficult to see in this photo, but ATI marks the flexplate with the “Engine Side”. OEM flexplates often have stamped pads that can only go on one way.
I use ARP fasteners and torque them to ARP specs (not the OEM manufacturer specification). There’s a reason for the potential difference in torque specs: It is because assembly lube can change the amount of torque required to tighten a specific fastener. ARP includes a packet of assembly lube with the bolt kit. When using ARP assembly lube, it’s important to follow the included instructions. Not only does the threaded portion of the fastener require lube – so does the under head area.
: I prefer to use ATI's Grade 8 bolts for the converter (to the flexplate). The reason is, a six-point head allows open end wrench access up inside the transmission bell housing.
Another thing folks tend to miss is transmission bolt engagement (often too little). I use ARP 12-point fasteners here, and this photo shows how much thread engagement they offer.
Cylinder block and transmission case faces must be clean and free of burrs and old paint. ATI suggests you use a file to clean and smooth the surface. If the transmission does not sit flush, it will constantly hurt seals and bushings. It can also lead to transmission case ear failure.
When installing the transmission, you shouldn't draw it to the block by the bolt threads. Once on the dowels, you should be able to move it into place by hand (that's what is going on here). Dowels must be firmly in the block and in good condition.
Something small but incredibly important is the transmission dipstick. I use this setup from Dan Masta's Trick Stick company. With this assembly, the dipstick actually locks (NHRA requirement). This prevents it from blowing out, and if you've ever experienced a broken automatic that spews out a dipstick tube (and consequently oils down your back tires), you'll know why it's a great idea!
ATI notes that the transmission cooler and lines must be clean and in good condition. If you had a previous transmission or converter failure, thoroughly flush the cooler and lines with a radiator cleaner/flush (available at most local auto parts stores). Repeat the process in both lines and then blow air through the system (in both directions). If any restrictions are noticed in the cooler or lines, they must be replaced.
I try to follow OEM cooler line routing paths, or at least something similar (keeping in mind the hose I use is larger in diameter than the steel factory lines). Here you can see how the lines pass under the starter. I built a little bracket to affix the hose separator/clamp to an oil pan bolt. Remember when routing cooler lines, you need to stay away from the headers and at the same time, allow access to the starter.
